Military Trim Pot Part Number Breakdown App
How do Trimmer Potentiometers Work?
Trimmer Potentiometers or “Trim Pots” as they are often called are basically miniature three terminal variable resistors (potentiometers). Trim pots work on the same principle as potentiometers. Trim pots have three terminals two of which are connected to a resistive strip or resistive track, the third is connected to an adjustable wiper. The position of the wiper on the resistive track determines the output voltage (as shown in the diagram). The material that’s used for the resistive element typically is made out of a carbon composition(Wirewound) or cermet. Usually trim pots are installed onto PCB’s (Printed Circuit Board) for fine tuning, (re)calibration, or any other type of adjustments in a circuit. When trim pots are used as replacements for regular potentiometers, adjustments should only be done when it’s absolutely necessary. Due to their size trim pots are very fragile, and most manufactures rate their lifespan at 200 cycles so frequent adjustments are not recommended. This rating applies to both Mil-Spec and commercial variants of trim pots.
RT/RTR & RJ/RJR Series Trim Pots
RT/RTR and RJ/RJR series trim pots are made to military specifications and are listed on the QPL (Qualified Parts List). Which simply means that they are on a government approved list of parts that are approved for government and military use. RT/RJ series trim pots are made to the MIL-PRF-22097 and the RTR/RJR series trim pots are made to the MIL-PRF-39035. The major difference between RT/RJ and the RTR/RJR series is that the RTR/RJR trim pots are offered with a failure rate. A failure rate is the frequency at which a component fails during testing over a set period of time. RTR/RJR series of trim pots are offered in three failure rate levels:
Note: Failure per 1000 hours of testing
- M = 1.0%
- P = 0.1%
- R = 0.01%
Although the RJ/RJR series and the RT/RTR series look pretty much identical, they have two different restive elements used for the resistive track that the wiper follows.
- RT/RTR = Wirewound
- RJ/RJR = Cermet
Please note that we at Federal Connectors recommend the RJ/RJR series trim pots over the RT/RTR series trim pots. Due to the RT/RTR series slowly becoming obsolete, there has been an increase in price of trim pots in that series. Another factor to take in consideration is longer lead times for trim pots that are out of stock from the RT/RTR series.
All the series of trim pots mentioned above are a sealed style trim pot, which means that the resistive track and the wiper are covered by a protective material. These trim pots are available in a wide variety of resistance ranges. Depending on the series, these trim pots they may either have a temperature rating of -55°C to 150°C or -65°C to +150°C. Since trim pots are designed for making small adjustments to electrical circuits and are usually mounted to a PCB (Printed Circuit Board), they relatively have a low rotational life. Both the RT/RTR and the RJ/RJR series of trim pots are rated at 200 cycles (For more info take a look at the spec. tables below). Differentiating between manufactures is relatively easy, Bourns trim pots are blue in color and VRN trim pots are green (As shown in the images below).
RT12 - Bourns
RT12 - VRN
| RT/RTR Specifications | ||||||||
|---|---|---|---|---|---|---|---|---|
| Series | Mil-Pref | Power Rating | Size (in") | Standard Resistance Range | Absoulute Minimum Resistance | Temp. Range | Adjustment Travel | Torque |
| RT12 | MIL-PRF-27208 | 70°C 1 Watt | 1 1/4 | 10 - 20K ohms | 0.1% or 1ohm max | -55°C to +150°C | 22 turns nominal | 5.0 oz-in. max |
| RT22 | MIL-PRF-27208 | 85°C 0.75 Watt | 1/2" | 50 - 20K ohms | 0.1% or 1ohm max | -65°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RTR22 | MIL-PRF-39015 | 85°C 0.75 Watt | 1/2" | 500 - 20K ohms | 0.1% or 1ohm max | -65°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RT24 | MIL-PRF-27208 | 85°C 0.25 Watt | 3/8" | 10 - 10K ohms | 0.1% or 1ohm max | -65°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RTR24 | MIL-PRF-39015 | 85°C 0.25 Watt | 3/8" | 500 - 10K ohms | 0.1% or 1ohm max | -65°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RT26 | MIL-PRF-27208 | 85°C 0.25 Watt | 1/4" | 10 - 5K ohms | 0.25% or 1ohm max | -55°C to +150°C | 11 turns nominal | 3.0 oz-in. max |
| RJ/RJR Specifications | ||||||||
|---|---|---|---|---|---|---|---|---|
| Series | Mil-Pref | Power Rating | Size (in") | Standard Resistance Range | Absoulute Minimum Resistance | Temp. Range | Adjustment Travel | Torque |
| RJ12 | MIL-PRF-22097 | 70°C 1 Watt | 1 1/4 | 10 ohms - 1 megohm | 1% or 2ohms max | -55°C to +150°C | 22 turns nominal | 5.0 oz-in. max |
| RJ22 | MIL-PRF-22097 | 85°C 0.25 Watt | 1/2" | 10 ohms - 1 megohm | 1ohm max | -65°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RJ24 | MIL-PRF-22097 | 85°C 0.50 Watt | 3/8" | 10 ohms - 1 megohm | 2% or 20ohms max | -55°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RJR24 | MIL-PRF-39035 | 85°C 0.50 Watt | 3/8" | 10 ohms - 1 megohm | 2% or 2ohms max | -55°C to +150°C | 25 turns nominal | 5.0 oz-in. max |
| RJ26 | MIL-PRF-22097 | 85°C 0.25 Watt | 1/4" | 10 - 1 megohm | 2% or 20ohm max | -65°C to +150°C | 12 turns nominal | 3.0 oz-in. max |
| RJR26 | MIL-PRF-39035 | 85°C 0.25 Watt | 1/4" | 10 - 1 megohms | 2% or 2ohms max | -65°C to +150°C | 12 turns nominal | 3.0 oz-in. max |
| RJ50 | MIL-PRF-27208 | 85°C 0.50 Watt | 1/4" | 10 - 1 megohms | 1% or 2ohms max | -55°C to +150°C | 1 turn (240°) nominal | 5.0 oz-in. max |
| RJR50 | MIL-PRF-39035 | 85°C 0.50 Watt | 1/4" | 10 - 1 megohms | 1% or 2ohms max | -55°C to +150°C | 1 turn (240°) nominal | 5.0 oz-in. max |
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Federal Connectors is a supplier of Military Connectors, Military Fuses, Military Potentiometers, Military Resistors, Military Relays and other electronic components to the US government and various subcontractors. Our team at Federal Connectors has been serving government agencies and industrial organizations throughout the electronics community for over 25 years. We provide our customers with an easy shopping experience and reliable fulfillment.