Resistor Basics: Types of Resistors
I Introduction
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There is a wide range of types of resistors, and with the development of electronic technology, new types of resistors will continue to increase.
Resistors are generally divided into two categories: fixed resistors and variable resistors. Fixed resistors can be divided into two types of wire-wound type and non-wire-wound type according to the material of the resistor body. The non-wire-wound type resistors can also be divided into two types: film type and composite type; according to the structure of the resistor, it can be divided into tubular resistors, disc resistors and planar resistors, etc .; according to the form of the lead wire, the resistors can be divided into lead type, radial lead type, co-lead type and no lead type, etc. . According to different protection methods, resistors can be divided into unprotected, painted, plastic pressed, sealed and vacuum sealed.
This article will mainly introduce the classification of resistors, as well as the characteristics, advantages and disadvantages of different types of resistors. It is definitely worth reading as the basics of resistor.
Types of Resistor
Catalog
II Classification of Resistors Based on Material
2.1 Film Resistor
(1) Carbon Film Resistor
Carbon film resistors are made by depositing crystalline carbon which is thermally decomposed by vacuum high temperature on a cylindrical or tubular ceramic skeleton. Control the thickness of the carbon film and the groove to control the resistance value.
Carbon film resistors have good stability, low negative temperature coefficient, good high-frequency characteristics, less influenced by voltage and frequency, less electric noise, stable pulse load, wide resistance range, simple production process, low production cost. So it is widely used in various electronic products.
Figure1. The Appearance and Structure of Carbon Film Resistor
(2) Metal Film Resistor
Metal film resistors are made by heating and evaporating metal or alloy materials on a ceramic substrate to form a thin film on the ceramic substrate. They can also be manufactured by methods such as pyrolysis, chemical deposition, and infiltration.
Metal film resistors have good stability and heat resistance, a small temperature coefficient, a large operating frequency range, and a small noise electromotive force. They are often used in high-frequency circuits.
Figure2. Metal Film Resistor
(3) Metal Oxide Film Resistor
Metal oxide film resistors are made by spraying metal salt solutions (tin tetrachloride and antimony trioxide), such as tin and antimony, onto the surface of the hot ceramic skeleton in a heating furnace at about 550 ° C and depositing them. The conductive film layer of this kind of resistor is uniform, the film and skeleton matrix are firmly combined, and some performances are better than metal film resistors. The shape of the ordinary metal oxide film resistor is basically the same as that of the metal film resistor, and its structure is mostly cylindrical and is an axial lead-out wire.
Metal oxide film resistors have stronger oxidation resistance, acid resistance and salt resistance than metal film resistors, and have good heat resistance. The disadvantage of metal oxide film resistors is that due to the limitations of material characteristics and film thickness, the resistance range is small, and the resistance range is 1Ω ~ 200 kΩ; the rated power is 1/8 ~ 10 W; 25 W ~ 50 kW.
Figure3. Metal Oxide Film Resistor
2.2 Composition Resistor
Composition resistors can be divided into solid core resistors and paint film resistors according to resistor shape; they can be divided into organic types (such as phenolic resin) and inorganic types (such as glass, ceramics, etc.) according to the type of binder. It can be divided into general-purpose type, high-resistance type and high-pressure type according to usage.
The most prominent advantage of synthetic resistors is high reliability. For example, the reliability of high-quality solid-core resistors is usually 5 to 10 times higher than that of the metal film and carbon film resistors. Therefore, despite its poor electrical performance (large noise, poor linearity, low accuracy, poor high-frequency characteristics, etc.), due to its high reliability, it is still widely used in some special fields, such as the aerospace industry, submarine cables Wait. Here are some common synthetic resistors.
(1) Solid Core Resistor (model S)
The common model is RS11 type, the resistance value range is 4.7Ω &#; 22MΩ, the accuracy is ± 5%, ± 10%, ± 20%, the volume is the same as the metal resistor at the same power.
(2) High Voltage Composite Film Resistor
Common domestic models are RHY-10 and RHY-35. The withstand voltage of the former can be 10kV, and the latter can reach 35kV; the resistance range is 47MΩ ~ MΩ, and the accuracy is ± 5% and ± 10%.
(3) Carbon Film Composition Resistor
Carbon Film Composition resistors are made by mixing carbon black, filler and organic binder into a suspension, coated on an insulating skeleton, and polymerized by heating. Its resistance range is high, which can reach 10 ~ 106 MΩ; rated power is 1/4 ~ 5 W; maximum working voltage is 35kV. The disadvantages are poor moisture resistance, low voltage stability, poor frequency characteristics, and high noise.
This kind of resistor is not suitable for general-purpose resistors, but mainly suitable for high-voltage and high-resistance resistors. It is usually packaged in a glass shell to make a vacuum megohm resistor for micro-current testing.
(4) Organic Solid Composition Resistor
Organic Solid Composition resistors are made of carbon black, graphite and other conductive substances and fillers mixed with organic binders to form powders, which are hot pressed by special equipment and made into plastic shells. The leads of solid resistors are compression molded in the resistor body. One is a resistor without end cap, and the other is a resistor with end cap and using the end cap as an electrode.
This resistor has high mechanical strength, good reliability, and strong overload capacity; small size and low price; large inherent noise, large distribution parameters, poor voltage and temperature stability, and resistance range of 4.7Ω ~ 22 MΩ; Working voltage is 250 ~ 500 V; rated power is 1/4 ~ 2 W.
However, such resistors are not suitable for use in demanding electrical circuits. At present, common organic synthetic solid resistors are RS11 type and RS type. RS type organic solid resistors are commonly used in automobile instruments (oil pressure gauges).
(5) Glass Glaze Resistor
The glass glaze resistor is made of metal silver, rhodium, ruthenium and other metal oxides mixed with glass glaze adhesive to form a slurry, which is coated on the ceramic skeleton and sintered at high temperature. At present, resistors are often made of ruthenium oxide and glass glaze adhesives. Metal glass glaze resistors have ordinary and precision types.
This resistor has high-temperature resistance, good humidity resistance, good stability, low noise, small temperature coefficient, large resistance range, resistance range is 4.7Ω ~ 200 MΩ; rated power is 1/8 W, l / 4 W, l / 2 W, 1 W, 2 W, high power 500 W; maximum voltage is 15 kV.
Figure4. Different Types of Resistors
2.3 Alloy Resistor
(1) Precision Wire Wound Resistor (model RX)
In the measurement instrument into other circuits that require high precision, precision wire-wound resistors can be used. The resistance of such resistors is generally ± 0.01%, up to 0.005% or higher, the temperature coefficient is less than l0-6 &#;, and the long-term working stability is high , The resistance range can be between O.O1Ω ~ lOMΩ. However, this type of resistor is not suitable for use in high-frequency circuits because the process is wire wound, so the distribution parameters are large.
Figure5. Presicion Wire Wound Resistor
(2) Power Type Wire Wound Resistor (model RX)
The rated power of this resistor is above 2W, the maximum power can reach 200W, the resistance range is 0.15Ω to hundreds of kΩ, and the accuracy level is ± 5% &#; ± 20%. This type of resistance is divided into fixed type and adjustable type. The adjustable type draws a sliding head from the resistor body, which can adjust the resistance value, which is convenient for debugging in the whole machine.
(3) Precision Alloy Foil Resistor
This resistor has the function of automatically compensating for the temperature coefficient of the resistor, and can maintain a very small temperature coefficient in a wide temperature range, so it has the characteristics of high precision, high stability, high frequency and high-speed response, making up for the metal film and wire winding Insufficient resistance. The accuracy of this type of resistance can reach ± 0.001%, the stability is ± 5 × 10-5% / year, and the temperature coefficient is (0 ± 1) × 10-6 / &#;.
III Classification of Resistors Based on the Purpose
(1) General Type
Refers to the resistance that can meet the general technical requirements, the power is 0.05 (1/20 ~ 2W, the resistance value is 1Ω ~ 22MΩ deviation is ± 5 ~ ± 20%.
(2) Precision Type
Resistance with high precision and stability, the power is generally not greater than 2W, the resistance value is 0.01Ω ~ 20MΩ, the deviation is 2% ~ 001%.
(3) High Frequency Type
The inductance of the resistor itself is extremely small, often called non-inductive resistance. Used in high-frequency circuits, the resistance is less than 1kΩ, the power range is wide, and the maximum can reach 100W.
(4) High Voltage Type
Suitable for high-voltage devices, working at V ~ 100KV, high up to 35GV, power between 0.5 ~ 100W, resistance up to MΩ.
(5) High Resistance Type
The resistance is above 10 MΩ, up to Ω.
(6) Integrated Resistance
Combined with mask, lithography, sintering and other process technologies, multiple resistors with consistent parameters and performance are formed on a substrate, and connected into a resistor network. It has the characteristics of small size, regularization and high precision. It is suitable for electronic instruments and computer products.
(7) Insurance Type
Made of non-combustible metal film, it has the dual function of resistance and fuse, the resistance value range is 0. 33Ω &#; 10 KΩ. When the actual power is 30 times the rated power, 7s is off. When the actual power is 12 times the rated power, 30 ~ 120s off.
Figure6. Different Resistors
IV Types of Sensitive Resistors
(1) Thermistor
The thermistor can be divided into MF: negative temperature coefficient; MZ: positive temperature coefficient.
The thermistor is a resistor whose resistance value changes with temperature and is usually made of a semiconductor material such as single crystal or polycrystal. It is made of barium titanate as the main raw material, supplemented with trace amounts of strontium, titanium, aluminum and other compounds. It can be divided into negative temperature coefficient thermistors whose resistance decreases with increasing temperature and resistance increases with temperature The high and rising positive temperature coefficient thermistor has a slow change type and a sudden change type.
Thermistor is mainly used for temperature measurement, temperature control (temperature control of electromagnetic oven), fire alarm, meteorological sounding, microwave and laser power measurement, temperature compensation in radio, and demagnetization current limiting resistor in TV.
Figure7. Thermistor
(2) Photoresistor
A photoresistor is a kind of element made by using the photosensitive effect of semiconductors. The resistance value changes with the intensity of incident light. The stronger the light, the smaller the resistance. When there is no light irradiation, the high impedance resistance value can reach 1.5MΩ or more; when there is light irradiation, the material excites free electrons and holes, and its resistance value decreases. With the increase of light intensity, the resistance value can be as low as 1kΩ.
The photoresistor is made by coating materials sensitive to light on the glass and drawing out the electrodes. Depending on the material, a photosensitive resistor sensitive to a certain light source can be made. Such as: visible photoresistor, the main material cadmium sulfide, used in photoelectric control. Infrared photoresistor, the main material is lead sulfide, used in missile and satellite monitoring.
Figure8. Photoresistor
(3) Varistor
The varistor is a semiconductor ceramic element made of zinc oxide as the main material, and the resistance value changes according to the non-linear characteristics with the change of the voltage applied at both ends. When the voltage applied to both ends does not exceed a certain value, it shows high impedance, and the current flowing through the varistor is very small, which is equivalent to an open circuit. When the voltage exceeds a certain value, its resistance suddenly decreases, and the current flowing through the resistance increases sharply. Varistors are widely used in electronic and electrical circuits and are mainly used for overvoltage protection and as voltage stabilizing components.
Figure9. Metal Oxide Varistor
(4) Magneto-resistor
Magneto-resistors are made of materials such as indium arsenide or indium antimonide, based on the magnetoresistance effect of semiconductors, and the resistance increases with the increase of the magnetic flux passing through it. It is a semiconductor element sensitive to the magnetic fields, which can convert magnetic induction signals into electrical signals. Mainly used to measure the strength of the magnetic field, magnetic card text recognition, magnetoelectric coding, AC-DC conversion.
Figure10. Magneto Resistor
(5) Force Sensitive Resistor
The resistance becomes larger as the applied stress changes. It is a special element that can transform force into an electrical signal. Commonly used in sensors such as tensiometers, accelerometers, semiconductor microphones.
Figure11. Force Sensitive Resistor
(6) Gas-sensitive Resistor
Made of semiconductor materials such as tin dioxide. After absorbing a certain gas on the surface of the semiconductor, an oxidation or reduction reaction occurs, and the resistance changes with the concentration of the measured gas.
Gas-sensitive resistors are often used in gas detectors, such as the electronic nose mounted on range hoods, and are also used to measure automobile exhaust, drunk driving and other devices.
Figure12. Gas-sensitive Resistor
(7) Humidity Resistor
The resistance of the humidity-sensitive resistor changes with the change of the relative humidity of the environment, and the surface moisture content can be measured.
Figure13. Humidity Resistor
V Types of Potentiometer
5.1 What is a Potentiometer?
The potentiometer is a kind of resistor with adjustable resistance, which is derived from the variable resistor. The general potentiometer is composed of a resistor body, a sliding arm, a rotating handle (sliding handle), a housing and a soldering piece.
In addition to ordinary potentiometers, there are potentiometers with switches, which are controlled by the rotary handle. Traditionally, the adjustable resistance with handle and housing is generally called a potentiometer, the one without handle or without housing is called a trimming resistor, and it is also called a preset resistance.
5.2 Classification of Potentiometers
(1) Classification by Material
Carbon film: Carbon film is used as a resistance film.
Metal Film: A special ceramic film made of ceramic and metal is used as a resistance film.
Wirewound: A metal wirewound is used as a resistor. Compared with carbon film or porcelain gold film, it can withstand greater power.
(2) Classification by Structure
Rotating: common form. The usual rotation angle is about 270 to 300 degrees.
Single-turn type: a common form.
Multi-turn type: used for occasions requiring precise adjustment.
Linear sliding type: usually used in the mixer, it is easy to immediately see the position of the volume and do fade control.
(3) Classification by Quantity
Single connection: One rotary shaft only controls a single potentiometer.
Double-connected: Two potentiometers are controlled by the same shaft, which is mainly used in dual-channel, which can control two channels at the same time.
(4) Classification According to the Change Scale of Resistance Value
Linear scale type: The change in resistance value is linearly related to the rotation angle or moving distance. This type of potentiometer is called a B-type potentiometer.
Logarithmic scale type: The change of resistance value is a logarithmic relationship with the rotation angle or moving distance. The main purpose of this type of potentiometer is volume control, of which the type A potentiometer is commonly used, suitable for large volume in the clockwise direction and counterclockwise direction. For low volume; in addition, there is a C-type potentiometer with a logarithmic scale that changes in the opposite direction.
(5) Classification According to the Material of the Resistor
Potentiometers can be divided into wire-wound potentiometers and non-wire wound potentiometers according to the material of the resistor body. Wire-wound potentiometers can be divided into general wire-wound potentiometers, precision wire-wound potentiometers, high-power wire-wound potentiometers and preset wire-wound potentiometers. Non-wire wound potentiometers can be divided into two types: solid potentiometers and membrane potentiometers. The solid potentiometer is divided into an organic synthetic solid potentiometer, inorganic synthetic solid potentiometer and conductive plastic potentiometer. Membrane potentiometers are divided into carbon membrane potentiometers and metal membrane potentiometers.
(6) Classification by Adjustment Method
Potentiometers can be divided into rotary potentiometers, push-pull potentiometers, straight slide potentiometers, etc. according to the adjustment method.
(7) Classification According to the Change Law of Resistance Value
Potentiometers can be divided into linear potentiometers, exponential potentiometers and logarithmic potentiometers according to the change rule of resistance value.
(8) Classification According to Structural Characteristics
Potentiometers can be divided into single-turn potentiometers, multi-turn potentiometers, single-connect potentiometers, double-connect potentiometers, multi-connect potentiometers, tapped potentiometers, switch potentiometers, locking potentiometers There are many types of non-locking potentiometers and patch-type potentiometers.
(9) Classification by Driving Method
Potentiometers can be divided into manual adjustment potentiometers and electric adjustment potentiometers according to the driving mode.
Figure14. Potentiometer
VI Introduction of Common Resistors and A List of Advantages and Disadvantages
6.1 Mind Map of Resistor Classification
Figure15. Mind Map of Types of Resistor
6.2 Brief Introduction and Advantages & Disadvantages of Commonly Used Resistors
Resistor
Introduction
Application Range
Advantage
Disadvantage
Carbon Film Resistor (RT)
Hydrocarbons decompose in high temperature and vacuum and deposit on porcelain rods or tubes to form a crystalline carbon film. Different resistance values can be obtained by changing the thickness and length of the carbon film.
&#;The main tolerances are:
± 5%, ± 10%, ± 20%&#;
&#;Mostly used in less demanding circuit occasions.
Low cost of carbon film
Poor stability and large errors
Metal Film Resistor (RJ)
Heating the alloy in a vacuum, the alloy evaporates, forming a conductive metal film on the surface of the ceramic rod. The resistance can be controlled by changing the thickness of the metal film.
&#;The allowable errors are: ± 0.1%, ± 0.2%, ± 0.5%, ± 1%.
&#;Mostly used in occasions with high accuracy requirements.
Small size, low noise and good stability
High cost
Metal Oxide film resistor (RY)
The metal salt solution of tin and antimony is sprayed onto the surface of the hot ceramic skeleton and formed by hydrolysis and deposition.
It is suitable for non-combustible, temperature change resistance, humidity resistance and other occasions.
Good oxidation resistance and thermal stability
-
Wire Wound Resistor
(RX)
Suitable for circuits with low frequency and high accuracy requirements.
Precise resistance, stable operation, small temperature coefficient, good heat resistance, and high power
The resistance value is small, the distributed inductance and distributed capacitance are large, and the manufacturing cost is also high
High power wire wound resistor (RX)
It is made of constantan or nickel-chromium alloy resistance wire wound on the ceramic skeleton.
Suitable for high power occasions, the rated power is generally more than 1W.
Stable work, good heat resistance, small error range
-
Organic Solid Resistor (RS)
The organic solid resistor is a resistor composed of granular conductive materials, fillers and adhesives, evenly mixed and then hot pressed together, and then installed in a plastic shell. Its leads are directly molded in the resistor body.
Generally used in places where the load cannot be disconnected and the work load is large, such as the circuit where the audio output is connected to the headset
Strong overload capacity, high reliability and low price
Low Precision
Fusing Resistor (RF)
A fuse resistor is an element with dual functions of resistance and fuse.
It is used in series with high value and circuit components that need to be protected. It is commonly used in power supply and secondary power supply circuits.
-
-
Cement Resistor(RX)
Cement resistor is also a fuse resistor, which is formed by winding the resistance wire on the heat-resistant ceramics, and protecting it with heat-resistant, moisture-resistant and corrosion-resistant materials.
A Good choice in a circuit where a large amount of current is being passed through a resistor and with it needing to be resistant to high heat and flame.
Good explosion-proof performance, complete insulation, shock resistance, humidity resistance, heat resistance and good heat dissipation
Large size, high heat generation during use, easy to radiate
0 ohm Resistor
Zero-ohm resistors, also called jumper resistors, are resistors used for special purposes.
&#;On the PCB for debugging convenience or compatible design and other reasons
&#;Can be used as a jumper
&#;Wiring
-
-
Power Type Wire Wound Non-inductive Resistor (aluminum shell resistor)
&#;A special wire-wound method is adopted, which makes the inductance much lower than that of general wire-wound resistors.
&#;Adopt a metal shell to facilitate heat dissipation.
It is suitable for high-power circuits and harsh magnetic fields, so it is often called a power resistor.
-
-
Network Resistor(Wire-wound Resistor)
Network resistor is made by encapsulating several resistors with the same parameters together and combining them.
Generally used in digital circuits, instrument circuits and computer circuits, such as attenuators in instrument circuits.
Easy assembly and high installation density
-
6.3 The List of Types of Resistors
Classify by uses
Classify by Materials
Wire Wound Type
Film Type
Composite Type
Carbon Film Type
Metal Film Type
Metal Oxide Film Type
Glass Glaze Type
Composite Carbon Film Type
Metal Foil Type
Organic Solid Type
Inorganic Solid Type
General Type
&#;
&#;
&#;
&#;
&#;
&#;
&#;
Precision Type
&#;
&#;
&#;
&#;
High-resistance Type
&#;
&#;
&#;
Power Type
&#;
&#;
&#;
High-voltage Type
&#;
&#;
High-frequency Type
&#;
VII One Question Related to Resistor Classification
1. What are the functions of a resistor?
A resistor is a material which opposes or resists the flow of current in electronic circuits.
When the load connected at the output is larger i.e. if it draws higher current, it would be burnt and there are the chances of short circuit. So, in order to limit such current flow, we use resistors.
There are also resistors known as 0-ohm resistors which can be used as jumpers. That is, it connects one electrical path to another, and it may not affect the conductivity as it has 0-ohm resistance.
2. How does a resistor work?
Voltage is like water pressure and current is like flow-rate. If you have a big pipe with a high pressure and only want a small dribble then you can have a choke point in the pipe to restrict the flow-rate. We call these taps or faucets.
Resistors work in exactly the same way. We use a narrow wire to restrict the current. Sometimes we use a wire that is inherently worse at being a conductor. The difference between water and electricity is that a tap is a single point of restriction but materials resist electricity in proportion to their length and in inverse proportion to the cross-sectional area. A short thick wire resists less than a long thin wire. And different materials resist more or less than other materials.
So a resistor is just a length of some material that resists the current. It might be long thin wire or it might be some other material such as carbon.
3. Why are resistors important?
Resistors are the most basic & most important passive elements. There must be at least one resistor in every electronics circuit.
Resistors are used to mainly limit the current. But it is also used in many other occasions such as lower the voltage (by Voltage divider rule). It is very useful in low powered circuit, such as when we use any module with Arduino, most of the modules run at 3.3V, but Arduino can supply 5V. So, we use two resistors to convert 5V to 3.3V to avoid feeding 5V, where 3.3V is needed. We also use this voltage divider technique in fan speed regulators, dimmable light by using potentiometer (variable resistor, so that we can tune any amount of resistance by turning a knob).
4. How are resistors classified?
All modern fixed value resistors can be classified into four broad groups: Carbon Composition Resistor &#; Made of carbon dust or graphite paste, low wattage values. Film or Cermet Resistor &#; Made from conductive metal oxide paste, very low wattage values.
5. Where are resistors used?
In electronic circuits, resistors are used to reduce current flow, adjust signal levels, divide voltages, bias active elements, and terminate transmission lines, among other uses.
6. What are the 2 general classifications of resistor?
Fixed resistors: Fixed resistors are by far the most widely used type of resistor.
Variable resistors: These resistors consist of a fixed resistor element and a slider that taps onto the main resistor element.
7. What is the resistor formula?
To calculate the total overall resistance of a number of resistors connected in this way you add up the individual resistances. This is done using the following formula: Rtotal = R1 + R2 +R3 and so on. Example: To calculate the total resistance for these three resistors in series.
8. What is the difference between resistor and resistance?
Resistance is the property of a conductor, which determines the quantity of current that passes through it when a potential difference is applied across it. A resistor is an electrical component with a predetermined electrical resistance, like 1 ohm, 10 ohms 100 ohms ohms, etc.
9. What is a wire-wound resistor?
A wire-wound resistor is an electrical passive device that limits or restricts current flow in a circuit. ... The conductive wire can be made of varying alloys and thicknesses to control the resistance value. Wirewound resistors are typically used in high power and industrial applications such as circuit breakers and fuses.
10. What is a cement resistor?
Cement resistors are power resistors that are heat and flame-resistant. Cement resistors are made to handle a large amount of power flowing through it with it being undamaged by heat or flames.
bill williams
#
I am currently rebuilding some old test gear, and one piece in particular is a B&K tube tester from the mid-late 50s. In going through the schematic & parts list, almost all the resistors were identified as 'glass' and almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this description of a resistor. Can someone shed some light on what exactly a glass resistor is and its major characteristics? (pointers to correct descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the resistor from effects of moisture, but I am not sure about that because with a tolerance of 5%, changes in resistance due to moisture would be small in comparison to any variation due to 5% tolerance. Perhaps long term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but if I do, I don't know the appropriate material to use, e.g. metal film, etc., without understanding what I'll be trading off.
With much appreciation,-John
[Non-text portions of this message have been removed]
tronix_cal
#
glass encased metal film resistor. I've seen them used in aircraft UHF
transmitters, only time I've seen one - low capacity?. The Corning
units are usually grey enamel over the film, which is on the glass
rod/substrate "core" and usually have the Corning "CGW" printed on them...
On 03/06/ 04:49 PM, bill williams uniquelogin@...
[TekScopes] wrote:
I am currently rebuilding some old test gear, and one piece in
particular is a B&K tube tester from the mid-late 50s. In going
through the schematic & parts list, almost all the resistors were
identified as 'glass' and almost all the glass resistors had a
tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this
description of a resistor. Can someone shed some light on what
exactly a glass resistor is and its major characteristics? (pointers
to correct descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield
the resistor from effects of moisture, but I am not sure about that
because with a tolerance of 5%, changes in resistance due to moisture
would be small in comparison to any variation due to 5% tolerance.
Perhaps long term stability is of concern?
It is not clear that I need to replace any of these glass resistors,
but if I do, I don't know the appropriate material to use, e.g. metal
film, etc., without understanding what I'll be trading off.
With much appreciation,-John
Corning made a metal film over glass resistor, and Richey also made aglass encased metal film resistor. I've seen them used in aircraft UHFtransmitters, only time I've seen one - low capacity?. The Corningunits are usually grey enamel over the film, which is on the glassrod/substrate "core" and usually have the Corning "CGW" printed on them...On 03/06/ 04:49 PM, bill williams uniquelogin@...[TekScopes] wrote:
Bruce Griffiths
#
Victoreen used to make glass encapsulated high value carbon film resistors.
Bruce
toggle quoted message
Show quoted text
On 07 March at 10:49 "bill williams uniquelogin@... [TekScopes]" <TekScopes@...> wrote:
I am currently rebuilding some old test gear, and one piece in particular is a B&K tube tester from the mid-late 50s. In going through the schematic & parts list, almost all the resistors were identified as 'glass' and almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this description of a resistor. Can someone shed some light on what exactly a glass resistor is and its major characteristics? (pointers to correct descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the resistor from effects of moisture, but I am not sure about that because with a tolerance of 5%, changes in resistance due to moisture would be small in comparison to any variation due to 5% tolerance. Perhaps long term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but if I do, I don't know the appropriate material to use, e.g. metal film, etc., without understanding what I'll be trading off.
With much appreciation,-John
David Hess
#
The modern hermetically sealed glass resistors I have seen are
extremely high values with tight tolerances where contamination would
be a serious problem.
If the resistors are used at high voltages, then high voltage thin or
thick film resistors are probably suitable replacements.
toggle quoted message
Show quoted text
I am currently rebuilding some old test gear, and one piece in particular is a B&K tube tester from the mid-late 50s. In going through the schematic & parts list, almost all the resistors were identified as 'glass' and almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this description of a resistor. Can someone shed some light on what exactly a glass resistor is and its major characteristics? (pointers to correct descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the resistor from effects of moisture, but I am not sure about that because with a tolerance of 5%, changes in resistance due to moisture would be small in comparison to any variation due to 5% tolerance. Perhaps long term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but if I do, I don't know the appropriate material to use, e.g. metal film, etc., without understanding what I'll be trading off.
With much appreciation,-John
On Mon, 6 Mar 21:49:20 + (UTC), you wrote:
Fabio Trevisan
#
I think the term is not very used anymore but I think it refers to the
resistors' insulation material and, being glass (instead of lacquer), it's
capable of withstanding higher voltage.
For relatively high value resistors, for which voltage is not limited by
its power rating, a regular lacquer coated resistor is rated at around 300V
while a "not so special" glass coated resistor can withstand 3kV (again, as
long it's not being limited by the dissipated power).
In Brazil is still common, if you go to a parts store and ask the salesman
for a high voltage rating resistor, they refer to it as "glass" resistors.
Nowadays, it's much more about the ratings and the different brands'
classes / categories and one is no longer much more concerned as of what
material the darn thing is made of, as long as it meets the specs... But
back when that particular quality was introduced (e.g. such as being able
to stand 3kV) the term was coined relating that particular outstanding spec
to the material that it was made of.
I'm not sure, today, if all resistors capable to stand 3kV are necessarily
coated with glass, or if there maybe new materials that do as as good as.
Brgrds,
Fabio
On Mar 6, 6:50 PM, "bill williams uniquelogin@...
[TekScopes]" <TekScopes@...> wrote:
The modern hermetically sealed glass resistors I have seen are
extremely high values with tight tolerances where contamination would
be a serious problem.
If the resistors are used at high voltages, then high voltage thin or
thick film resistors are probably suitable replacements.
On Mon, 6 Mar 21:49:20 + (UTC), you wrote:
I am currently rebuilding some old test gear, and one piece in particular
is a B&K tube tester from the mid-late 50s. In going through the schematic
& parts list, almost all the resistors were identified as 'glass' and
almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this
description of a resistor. Can someone shed some light on what exactly a
glass resistor is and its major characteristics? (pointers to correct
descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the
resistor from effects of moisture, but I am not sure about that because
with a tolerance of 5%, changes in resistance due to moisture would be
small in comparison to any variation due to 5% tolerance. Perhaps long
term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but
if I do, I don't know the appropriate material to use, e.g. metal film,
etc., without understanding what I'll be trading off.
With much appreciation,-John
[Non-text portions of this message have been removed]
Hi Bill,I think the term is not very used anymore but I think it refers to theresistors' insulation material and, being glass (instead of lacquer), it'scapable of withstanding higher voltage.For relatively high value resistors, for which voltage is not limited byits power rating, a regular lacquer coated resistor is rated at around 300Vwhile a "not so special" glass coated resistor can withstand 3kV (again, aslong it's not being limited by the dissipated power).In Brazil is still common, if you go to a parts store and ask the salesmanfor a high voltage rating resistor, they refer to it as "glass" resistors.Nowadays, it's much more about the ratings and the different brands'classes / categories and one is no longer much more concerned as of whatmaterial the darn thing is made of, as long as it meets the specs... Butback when that particular quality was introduced (e.g. such as being ableto stand 3kV) the term was coined relating that particular outstanding specto the material that it was made of.I'm not sure, today, if all resistors capable to stand 3kV are necessarilycoated with glass, or if there maybe new materials that do as as good as.Brgrds,FabioOn Mar 6, 6:50 PM, "bill williams uniquelogin@...[TekScopes]" wrote:[Non-text portions of this message have been removed]
David Holland
#
tube tester from B&K in the 50's. 300V resistors might be a little
low on the voltage rating, but 450V's would likely be more than
sufficient.
All I've ever seen in a service grade tube tester is standard carbon
comp's, an occasional power resistor, and *maybe* a precision wire
wound buried away in the meter. Service grade testers aren't
exactly precision equipment. Perhaps the wiz-bang Hickok's are
better, but I wouldn't hold my breath.
What make and model of B&K tester?
On Mon, Mar 6, at 7:00 PM, David davidwhess@... [TekScopes]
<TekScopes@...> wrote:
The modern hermetically sealed glass resistors I have seen are
extremely high values with tight tolerances where contamination would
be a serious problem.
If the resistors are used at high voltages, then high voltage thin or
thick film resistors are probably suitable replacements.
On Mon, 6 Mar 21:49:20 + (UTC), you wrote:
I am currently rebuilding some old test gear, and one piece in particular is a B&K tube tester from the mid-late 50s. In going through the schematic & parts list, almost all the resistors were identified as 'glass' and almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this description of a resistor. Can someone shed some light on what exactly a glass resistor is and its major characteristics? (pointers to correct descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the resistor from effects of moisture, but I am not sure about that because with a tolerance of 5%, changes in resistance due to moisture would be small in comparison to any variation due to 5% tolerance. Perhaps long term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but if I do, I don't know the appropriate material to use, e.g. metal film, etc., without understanding what I'll be trading off.
With much appreciation,-John
------------------------------------
Posted by: David <davidwhess@...>
------------------------------------
------------------------------------
Yahoo Groups Links
I'd consider neither criteria applicable in a standard service gradetube tester from B&K in the 50's. 300V resistors might be a littlelow on the voltage rating, but 450V's would likely be more thansufficient.All I've ever seen in a service grade tube tester is standard carboncomp's, an occasional power resistor, and *maybe* a precision wirewound buried away in the meter. Service grade testers aren'texactly precision equipment. Perhaps the wiz-bang Hickok's arebetter, but I wouldn't hold my breath.What make and model of B&K tester?On Mon, Mar 6, at 7:00 PM, David davidwhess@... [TekScopes] wrote:
Dennis Tillman W7pF
#
Tube testers do not use unusually high voltages. 200V volts is more than enough to test all of the + tube types used in common appliances (radios, TVs, stereo's, etc). Many tube testers test at much lower voltages.
You can tell most of what you need to know about the quality of a tube at lower plate voltages (under 100V). One exception are gas filled tubes like voltage regulators which need at least 80 to 100V to start the gas conducting current.
Dennis Tillman W7PF
toggle quoted message
Show quoted text
From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, March 06, 4:43 PM
To: TekScopes@...
Subject: Re: [TekScopes] Glass resistors - characteristics?
I'd consider neither criteria applicable in a standard service grade
tube tester from B&K in the 50's. 300V resistors might be a little
low on the voltage rating, but 450V's would likely be more than sufficient.
All I've ever seen in a service grade tube tester is standard carbon comp's, an occasional power resistor, and *maybe* a precision wire
wound buried away in the meter. Service grade testers aren't
exactly precision equipment. Perhaps the wiz-bang Hickok's are better, but I wouldn't hold my breath.
What make and model of B&K tester?
On Mon, Mar 6, at 7:00 PM, David davidwhess@... [TekScopes] <TekScopes@...> wrote:
The modern hermetically sealed glass resistors I have seen are
extremely high values with tight tolerances where contamination would
be a serious problem.
If the resistors are used at high voltages, then high voltage thin or
thick film resistors are probably suitable replacements.
On Mon, 6 Mar 21:49:20 + (UTC), you wrote:
I am currently rebuilding some old test gear, and one piece in particular is a B&K tube tester from the mid-late 50s. In going through the schematic & parts list, almost all the resistors were identified as 'glass' and almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this description of a resistor. Can someone shed some light on what exactly a glass resistor is and its major characteristics? (pointers to correct descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the resistor from effects of moisture, but I am not sure about that because with a tolerance of 5%, changes in resistance due to moisture would be small in comparison to any variation due to 5% tolerance. Perhaps long term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but if I do, I don't know the appropriate material to use, e.g. metal film, etc., without understanding what I'll be trading off.
With much appreciation,-John
------------------------------------
Posted by: David <davidwhess@...>
------------------------------------
------------------------------------
Yahoo Groups Links
------------------------------------
Posted by: David Holland <david.w.holland@...>
------------------------------------
------------------------------------
Yahoo Groups Links
-----Original Message-----From: TekScopes@... [mailto:TekScopes@...]Sent: Monday, March 06, 4:43 PMTo: : Re: [TekScopes] Glass resistors - characteristics?I'd consider neither criteria applicable in a standard service gradetube tester from B&K in the 50's. 300V resistors might be a littlelow on the voltage rating, but 450V's would likely be more than sufficient.All I've ever seen in a service grade tube tester is standard carbon comp's, an occasional power resistor, and *maybe* a precision wirewound buried away in the meter. Service grade testers aren'texactly precision equipment. Perhaps the wiz-bang Hickok's are better, but I wouldn't hold my breath.What make and model of B&K tester?On Mon, Mar 6, at 7:00 PM, David davidwhess@... [TekScopes] wrote:------------------------------------Posted by: David Holland ------------------------------------------------------------------------Yahoo Groups Links
#
http://bama.edebris.com/manuals/b&k/700/ http://bama.edebris.com/manuals/b&k/700/
Looking at the schematic, the highest voltage is approx 400 VDC.
I think Favio comment about the insulation quality is somewhat on point. They wanted to achieve a higher breakdown voltage. Still a little strange to me as I had my head in a lot of tube TVs in the mid 60s and don't remember glass resistors - then again, I was (very) young and poking around my dad's shop.
Also, Favio comment triggered a long forgotten repair effort. I accidently crushed the resistor in a 30KV HV probe that was used to check cathode voltage on CRTs. Disassembling it resulted in finding a long wire wound resistor on a glass rod (or form-dont recall) all encased in a glass tube. I assume the glass was for insulation/breakdown voltage....
So to be safe, I guess I should try to find resistors that have at least a 400v breakdown voltage, and probably 450 v or higher would be better...
J
It is a model 700. For the curious, the manual can be found here:Looking at the schematic, the highest voltage is approx 400 VDC.I think Favio comment about the insulation quality is somewhat on point. They wanted to achieve a higher breakdown voltage. Still a little strange to me as I had my head in a lot of tube TVs in the mid 60s and don't remember glass resistors - then again, I was (very) young and poking around my dad's shop.Also, Favio comment triggered a long forgotten repair effort. I accidently crushed the resistor in a 30KV HV probe that was used to check cathode voltage on CRTs. Disassembling it resulted in finding a long wire wound resistor on a glass rod (or form-dont recall) all encased in a glass tube. I assume the glass was for insulation/breakdown voltage....So to be safe, I guess I should try to find resistors that have at least a 400v breakdown voltage, and probably 450 v or higher would be better...
David Holland
#
missing decimal point.)..
All those "glass" resistors look like 3W, or 7W power resistors to me.
If I recall correctly, carbon comps were generally available up to
about 2W, and after that you had to get more esoteric. But
generally speaking, beyond power dissipation, higher wattage resistors
(usually) have higher voltage ratings as well.
I don't think there's much of anything special about those resistors
beyond their power rating.
In your 30KV probe example, in that case, yes, they wanted the higher
voltage rating. In this case, I don't think it matters much. I
agree with Dennis, I think the most anything is going to see is about
200V.
IMHO, YMMV, of course...
David
On Mon, Mar 6, at 8:25 PM, uniquelogin@... [TekScopes]
<TekScopes@...> wrote:
It is a model 700. For the curious, the manual can be found here:
http://bama.edebris.com/manuals/b&k/700/ http://bama.edebris.com/manuals/b&k/700/
Looking at the schematic, the highest voltage is approx 400 VDC.
I think Favio comment about the insulation quality is somewhat on point. They wanted to achieve a higher breakdown voltage. Still a little strange to me as I had my head in a lot of tube TVs in the mid 60s and don't remember glass resistors - then again, I was (very) young and poking around my dad's shop.
Also, Favio comment triggered a long forgotten repair effort. I accidently crushed the resistor in a 30KV HV probe that was used to check cathode voltage on CRTs. Disassembling it resulted in finding a long wire wound resistor on a glass rod (or form-dont recall) all encased in a glass tube. I assume the glass was for insulation/breakdown voltage....
So to be safe, I guess I should try to find resistors that have at least a 400v breakdown voltage, and probably 450 v or higher would be better...
J
[Non-text portions of this message have been removed]
------------------------------------
Posted by: uniquelogin@...
------------------------------------
------------------------------------
Yahoo Groups Links
If I read (quickly skim) the parts list right.. (and there isn't amissing decimal point.)..All those "glass" resistors look like 3W, or 7W power resistors to me.If I recall correctly, carbon comps were generally available up toabout 2W, and after that you had to get more esoteric. Butgenerally speaking, beyond power dissipation, higher wattage resistors(usually) have higher voltage ratings as well.I don't think there's much of anything special about those resistorsbeyond their power rating.In your 30KV probe example, in that case, yes, they wanted the highervoltage rating. In this case, I don't think it matters much. Iagree with Dennis, I think the most anything is going to see is about200V.IMHO, YMMV, of course...DavidOn Mon, Mar 6, at 8:25 PM, uniquelogin@... [TekScopes] wrote:
Ed Breya
#
I think Fabio called it right - it's glass coating. There may be some confusion in the terminology used over the years - I'd guess that the original part type is the common vitreous enamel (like a molten glass glaze used in ceramics) coated wirewound power resistor. The wire is wound on a ceramic slug, and the outside is glazed, which makes a good high temperature insulation and seal.
Unless the parts were cooked or otherwise damaged, they should be impervious to most environment factors, and should not need replacement.
Ed
David Hess
#
being labeled "glazed". Except for thick film resistors, I always
considered film resistors to be low voltage until I ran across these.
(1)
Like I have described in the past, Tektronix replaced the carbon
composition resistors in high voltage circuits in the late 22xx series
with film resistors which seem to be related to the currently produced
VR or HVR film resistors (2) and the former are described as "glazed"
but I wonder what the difference is between these are and why one is
specified to be glazed and the other is not:
http://www.vishay.com/resistors-fixed/list/product-/
http://www.vishay.com/resistors-fixed/list/product-/
Even at 100s of volts, I would use these types of high voltage film
resistors to get enough voltage derating for reliability.
(1) Looking up metal glaze resistor reveals what is going on. They
*are* thick film resistors made from metal and glass powder fired onto
a substrate.
http://www.physics-and-radio-electronics.com/electronic-devices-and-circuits/passive-components/resistors/metalglazeresistor.html
(2) I never found specifications for the Mepco/Centralab resistors
that Tektronix used to replace the carbon composition resistors in
high voltage applications but I did find a reference indicating that
they became or were equivalent to the VR series of high voltage film
resistors.
That fits with some modern high voltage and high value film resistorsbeing labeled "glazed". Except for thick film resistors, I alwaysconsidered film resistors to be low voltage until I ran across these.(1)Like I have described in the past, Tektronix replaced the carboncomposition resistors in high voltage circuits in the late 22xx serieswith film resistors which seem to be related to the currently producedVR or HVR film resistors (2) and the former are described as "glazed"but I wonder what the difference is between these are and why one isspecified to be glazed and the other is not:Even at 100s of volts, I would use these types of high voltage filmresistors to get enough voltage derating for reliability.(1) Looking up metal glaze resistor reveals what is going on. They*are* thick film resistors made from metal and glass powder fired ontoa substrate.(2) I never found specifications for the Mepco/Centralab resistorsthat Tektronix used to replace the carbon composition resistors inhigh voltage applications but I did find a reference indicating thatthey became or were equivalent to the VR series of high voltage filmresistors.
toggle quoted message
Show quoted text
Hi Bill,
I think the term is not very used anymore but I think it refers to the
resistors' insulation material and, being glass (instead of lacquer), it's
capable of withstanding higher voltage.
For relatively high value resistors, for which voltage is not limited by
its power rating, a regular lacquer coated resistor is rated at around 300V
while a "not so special" glass coated resistor can withstand 3kV (again, as
long it's not being limited by the dissipated power).
In Brazil is still common, if you go to a parts store and ask the salesman
for a high voltage rating resistor, they refer to it as "glass" resistors.
Nowadays, it's much more about the ratings and the different brands'
classes / categories and one is no longer much more concerned as of what
material the darn thing is made of, as long as it meets the specs... But
back when that particular quality was introduced (e.g. such as being able
to stand 3kV) the term was coined relating that particular outstanding spec
to the material that it was made of.
I'm not sure, today, if all resistors capable to stand 3kV are necessarily
coated with glass, or if there maybe new materials that do as as good as.
Brgrds,
Fabio
On Mar 6, 6:50 PM, "bill williams uniquelogin@...
[TekScopes]" <TekScopes@...> wrote:
The modern hermetically sealed glass resistors I have seen are
extremely high values with tight tolerances where contamination would
be a serious problem.
If the resistors are used at high voltages, then high voltage thin or
thick film resistors are probably suitable replacements.
On Mon, 6 Mar 21:49:20 + (UTC), you wrote:
I am currently rebuilding some old test gear, and one piece in particular
is a B&K tube tester from the mid-late 50s. In going through the schematic
& parts list, almost all the resistors were identified as 'glass' and
almost all the glass resistors had a tolerance of 5%...some had 10%.
In all my dealings with electronics, I haven't come across this
description of a resistor. Can someone shed some light on what exactly a
glass resistor is and its major characteristics? (pointers to correct
descriptions?) Are they WW? carbon film? etc.
My initial reaction was a resistor encased in a glass tube to shield the
resistor from effects of moisture, but I am not sure about that because
with a tolerance of 5%, changes in resistance due to moisture would be
small in comparison to any variation due to 5% tolerance. Perhaps long
term stability is of concern?
It is not clear that I need to replace any of these glass resistors, but
if I do, I don't know the appropriate material to use, e.g. metal film,
etc., without understanding what I'll be trading off.
With much appreciation,-John
[Non-text portions of this message have been removed]
On Mon, 6 Mar 21:07:02 -, you wrote:
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