How to Test a Potentiometer with Analog Multimeter

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How to test a potentiometer with analog multimeter: choose an ohms range whose scale center is close to the part’s value, short the leads and turn the zero-ohm knob until the needle sits on zero, then read across the outer terminals and sweep the wiper while you watch the needle. A steady glide is the sign of a healthy track, while twitching or sudden swings point to a worn wiper. The needle bands for common values are in the table below.

Electrical safety first

Work on mains circuits can kill. OSHA’s fact sheet on working safely with electricity says that if the ground path is broken, fault current may travel through a worker’s body, causing electrical burns or death. A meter’s category rating must suit the circuit: Fluke’s page on IEC category ratings places receptacle-connected loads in CAT II and service entrances in CAT IV. Panel and service work belongs to a licensed electrician. OSHA’s general-industry rule allows only qualified persons to work on circuit parts that have not been de-energized, and Simpson’s manual for its 260 meter says the instrument should only be used by personnel qualified to recognize shock hazards.

The pages checked here are uneven on ratings. The GMT-312 manual describes measurement category II and ties its leads to CAT II 300 V. The Simpson 260 and Sanwa YX360TRF manuals, in the text opened for this guide, state no category. Sanwa describes its tester as designated for weak current circuits and says never to use it on circuits that exceed 3 kVA. If the listing or manual for your meter does not state a CAT rating, do not call it safe for household mains. This guide stays on the bench, on loose potentiometers or unpowered boards, in the ohms function only.

Quick answer

• Turn power off, discharge capacitors, and isolate the potentiometer before measuring.
• Pick the ohms range whose scale center is nearest the part’s value.
• Short the leads and set the needle to zero ohms again every time the range changes.
• Read the outer pair against the marked value, then sweep the wiper and look for any twitch or dropout.

What an analog ohmmeter does differently

An analog ohmmeter drives a small current from its own battery through the part and shows the result as a needle position. Two things follow. The ohms scale is not evenly spaced: the University of Hong Kong physics lab handout says the scale is usually non-linear, and the GMT-312 manual puts zero ohms at the right end of the scale. The battery also weakens with use, which is why the Simpson manual says its single ohms-adjust control compensates for variations in battery voltage and lets the user zero the instrument before measuring resistance.

Lead polarity is a smaller issue. The Hong Kong handout notes that the internal battery’s positive pole connects to the negative terminal of the meter, which matters for diodes and transistors. The Simpson manual says either function-switch position works for resistance, and the GMT-312 manual says lead polarity is not a factor in continuity checks. A potentiometer is a plain resistive track, so you can ignore polarity here. For a meter built mainly for resistance work, see our guide to ohm meters.

Choose the range by the scale center

The handout gives the rule: the part’s resistance and the meter’s internal resistance should be comparable. In practice, that means the needle should land near the middle of the scale. The Simpson 260-6XLM lists ohms centers of 6, 600, 6,000 and 60k ohms for its R x 1, R x 100, R x 1k and R x 10k ranges. The Sanwa YX360TRF lists a center value of 20 ohms and a maximum of 2 kilohms on its lowest range, and the handout adds that the reading is multiplied by the range factor. The table applies the Simpson figures to common potentiometer values. The needle band is our own arithmetic: the Bourns 3310 datasheet gives plus or minus 20 percent for its linear tapers, so the band runs from 0.80 to 1.20 times the nominal scale reading.

Marked value (ohms)	Range	Scale center (ohms)	Value ÷ center	Scale reading at nominal	Needle band, plus or minus 20 percent
1,000	R x 100	600	1.67	10	8 to 12
5,000	R x 1k	6,000	0.83	5	4 to 6
10,000	R x 1k	6,000	1.67	10	8 to 12
50,000	R x 10k	60,000	0.83	5	4 to 6
100,000	R x 10k	60,000	1.67	10	8 to 12

The scale reading is the part’s value divided by the range factor, and the handout’s own example shows the reverse: a needle at 7 on the x10k range means 7 × 10k, or 70k. Our reasoning, consistent with the handout’s remark that the scale is non-linear, is that a compressed scale makes each small needle movement near the left end stand for a larger change in ohms, so a range that puts the needle mid-scale is also the more readable one. Another series may have a different tolerance, so use the datasheet for your own part. The Simpson manual states its ohms accuracy as a figure of the scale arc, not of the reading.

The Simpson 260 also has low-power ohms ranges. Its manual says the 100 mV open-circuit voltage will not damage the circuit or have its resistance affected by conducting diodes. That helps on a board that has diodes in parallel, but it does not remove the other parallel paths, so isolate the part anyway. Our guide to the analog multimeter covers what to look for in the meter itself.

Zero the meter

Two zero adjustments exist, and both matter. The mechanical zero sets the needle at the left end of the scale when nothing is connected. The Simpson manual tells you to check it with the instrument in its operating position and to turn a screw below the center of the dial until the pointer rests freely over the mark. The GMT-312 manual describes the same screw and the same target at the left end.

The ohms zero is the one you repeat. For the Simpson 260 conventional ranges, turn the range switch to the desired range, short the test leads, and turn the ohms-adjust control until the pointer reads 0 on the black ohms arc. The manual says to replace the 1.5 V battery if it cannot reach 0, and to replace the 9 V battery if the R x 10k range cannot reach full scale. Sanwa gives the same steps and the same remedy: if the pointer fails to reach zero with the adjuster turned fully clockwise, fit a fresh battery. The GMT-312 manual warns that switching between ohms and other functions without re-zeroing gives inaccurate readings. All three procedures put the zeroing step after the range choice, so re-zero whenever you change range.

Keep the leads shorted only as long as the adjustment takes. The Simpson specification gives a maximum current of 250 mA from its 1.5 V battery on R x 1 with shorted leads, so a long short drains the cell. Lay the meter flat too: Simpson’s accuracy figures apply with the meter facing upward, and the GMT-312 manual advises a non-metallic surface.

Test 1: end-to-end resistance

1. Turn power off and isolate the potentiometer. Do not measure a component that is connected to a circuit, the Hong Kong handout says, and switch off the supply first.
2. Set the range from the table, short the leads and zero the needle.
3. Touch the probes to the two outer terminals and let the needle settle.
4. Multiply the scale reading by the range factor and compare it with the marked value and its band.

Turn the shaft partway. In an unloaded part the needle should not move, because the wiper is not part of the outer path. The Vishay Sfernice application note defines a potentiometer as a mechanically actuated variable resistor with three terminals, with the outer two linked to the ends of the track. If the needle rests at the infinity end, the track may be open, or the range may be too low.

Test 2: sweep the wiper

1. Keep one probe on an outer terminal and move the other to the middle terminal.
2. Turn the shaft slowly from stop to stop.
3. Repeat from the other outer terminal. The needle should move the opposite way.

This is where an analog meter earns its place. The Fluke 87 manual, describing the analog bar on its digital meter, says that like the needle on a VOM it excels at displaying trends or slowly changing signals, and that noisy resistance measurements create patterns. By our reading of those definitions, a healthy track gives a smooth glide, and a twitch, a flicker or a swing toward the infinity end points to a wiper that is losing contact. The Vishay note defines continuity as unbroken contact between wiper and element across the travel.

At each end of travel the reading should come close to zero ohms. The Bourns 3310 datasheet limits end resistance to 2 percent or 2 ohms, whichever is greater. We apply the percentage to the nominal value because the sheet does not say what it refers to, which gives 200 ohms for a 10,000 ohm part, or 200 ÷ 1,000 = 0.2 on the R x 1k scale. That is very close to the zero mark. The Bourns sheet also lists an effective electrical angle of 270 degrees and a mechanical angle of 295 degrees, so with nominal figures 295 − 270 = 25 degrees of travel do not follow the taper, and a still needle near each end can be normal.

Do not force the shaft. Vishay recommends axial efforts below 10 newtons and no radial effort, and on a multi-turn trimmer with a stop clutch it recommends not exceeding 10 screw turns at the clutch position.

Test 3: compare the halves with the total

With the wiper left in place, read A to B, then B to C, on the same range, zeroing first. Add the scale readings and compare them with the A to C reading. This check follows from the construction in the Vishay note, where the two sections are the track on either side of the wiper. Reading a needle by eye is coarse, so the sum will rarely match exactly, and the sources give no pass limit for the gap. Compare the gap at three or four shaft positions instead: it should stay small and steady as you turn.

Check the taper at mid-travel

The Vishay note defines resistance taper as the relationship between the position of the moving contact and the resistance. It uses code A for a linear taper and code L for a clockwise logarithmic, or audio, taper, with a checkpoint at 50 percent of electrical travel where the output ratio is 10 percent, give or take 3 percent. Other makers use other letters. For a 10,000 ohm part measured from the counter-clockwise end, which the note uses as its default reference, a linear taper should read 10,000 × 0.50 = 5,000 ohms at mid-travel, which is 5 on the R x 1k scale. An audio taper should read about 1,000 ohms, within 700 to 1,300 ohms, which is a small reading near the zero end of the R x 1k scale, so change to the R x 100 range, zero again, and look for 10 within 7 to 13, nearer the middle. Finding 50 percent of electrical travel by eye is rough, so use this only to tell a linear part from an audio part.

Keep the battery and the meter healthy

Three habits come straight from the manuals. The Simpson manual says never to leave the range switch on the low-power ohms position, because power is drawn continuously from the battery. The Hong Kong handout says to turn the range to a voltage or current mode after measuring so the internal battery is not drained by accident. The GMT-312 manual says to keep the switch in the OFF position when the meter is idle to stop the needle bouncing, and to remove the battery if the ohms function will not be used for a week or more.

How we chose

The procedure rests on three analog meter manuals (Simpson 260-6XLM, Sanwa YX360TRF and the GMT-312 owner’s manual), a University of Hong Kong physics handout, a Vishay Sfernice application note, a Bourns datasheet, the Fluke 87 manual, two OSHA pages and a Fluke category-rating page, all opened on 2026-10-21. We kept a step only when at least one of those pages states it, and we label our own arithmetic. Tolerance and end resistance figures come from one Bourns series. The licensed-electrician advice is a site rule, since OSHA speaks of qualified persons.

What we could not verify

None of the pages gives a pass limit for needle jitter, a failure threshold for a worn track, or a limit for the gap in the sum check. The Simpson accuracy figure is written in terms of scale arc, and the pages opened do not translate it into ohms for a given needle position. The Sanwa table in the text we read is hard to map line by line, so only its center and maximum values are used. None of the meter manuals or the handout describes testing a potentiometer, so the steps here apply their resistance procedures to that part.

Frequently asked questions

Which ohms range should I use for a 10k potentiometer?

Use the range whose scale center is closest to 10,000 ohms. On the Simpson 260-6XLM that is R x 1k, with a center of 6,000 ohms, and the needle should land near 10 on the scale.

Why does the needle not reach zero when I short the leads?

The battery is probably weak. The Simpson, Sanwa and GMT-312 manuals all say to replace the battery when the pointer cannot be brought to zero.

Does lead polarity matter for a potentiometer?

Not for a plain resistive track. Polarity matters for diodes and transistors, because the battery’s positive pole sits behind the negative terminal on the meter the Hong Kong handout describes, and Sanwa’s manual notes the same reversal.

Is an analog meter better than a digital one for a wiper sweep?

It shows trends well, and Fluke says the same of the analog bar on its digital meter. Fluke also says the fast analog display suits approximate adjustments and the digital display suits the final reading, so use the needle to spot dropouts and a digital number when you need one.

Can I test a potentiometer while it is wired into equipment?

Only a loose part or an unpowered board, with the part isolated. Parts in parallel change the reading, and equipment on mains is outside this guide.

Bottom line

Match the range to the part, zero the needle after every range change, and let the needle’s smoothness during the sweep decide whether the wiper is healthy.

Sources

• Simpson Electric, 260 Series 6XLM operator’s manual: https://www.instrumentation2000.com//media/pdf/simpson-260-6xlm-manual.pdf (opened 2026-10-21)
• Sanwa, YX360TRF multitester instruction manual: https://hardwarecity.com.sg/uploads/product/1633596688_SANWA%20YX-360TRF%20MANUAL.pdf (opened 2026-10-21)
• GMT-312 analog multimeter owner’s manual: https://images.homedepot-static.com/catalog/pdfImages/ff/ffac1e2b-008c-42dd-a57d-57e8d1ce4f50.pdf (opened 2026-10-21)
• University of Hong Kong physics laboratory, Multimeters and CROs handout: https://www.physics.hku.hk/~physlab/cyp206/multimeters%20and%20CROs.pdf (opened 2026-10-21)
• Vishay Sfernice, Potentiometers and Trimmers application note: https://www.farnell.com/datasheets/2884008.pdf (opened 2026-10-21)
• Bourns, 3310 9 mm square sealed panel control datasheet: https://www.bourns.com/docs/Product-Datasheets/3310.pdf (opened 2026-10-21)
• Fluke, 87 True RMS Multimeter Users Manual: https://assets.fluke.com/manuals/87______umeng0800.pdf (opened 2026-10-21)
• OSHA, Working Safely with Electricity fact sheet: https://www.osha.gov/sites/default/files/publications/OSHA3942.pdf (opened 2026-10-21)
• OSHA, 29 CFR 1910.333 selection and use of work practices: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.333 (opened 2026-10-21)
• Fluke, IEC Category Ratings: Use the Right Tools for the Job: https://www.fluke.com/en-us/learn/blog/safety/iec-category-ratings-use-the-right-tools-for-the-job (opened 2026-10-21)

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