MESR-100 ESR Meters Compared: 5 Listings Reviewed

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The MESR-100 is a small ESR meter that measures the internal series resistance of a capacitor, and a mesr 100 search turns up several near-identical listings. Five of them qualify, each from a different seller, and they do not describe the same level of detail. This guide compares them on the specs that matter for capacitor repair work: measuring range, resolution, in-circuit use, power source and how much the listing actually tells you. It also explains why 100kHz testing works and where the listings contradict themselves, so you know what to confirm before you order.

Quick answer

If you want the listing that states the most, choose the second choice: it gives a 0.000 to 100.0R range, a 4-digit display with 0.001Ohm resolution at the 1 Ohm range, up to 1% accuracy and two ways to power it. If you want a listing that names the V2 model and a stated 0.01R-100R span, choose the first. The other three, from different sellers, repeat the same theory text and give almost no specs.

Only five listings carry the right product type, so there is no sixth. Nothing in the other results, such as a pack of 1.5 volts AAA batteries, a 120W DIN rail power supply, a 600A clamp meter, a 3 W wind instrument, toothpick flags, miswak sticks or ovulation strips, is an ESR meter.

What an ESR meter does and why 100kHz matters

ESR means equivalent series resistance, the small resistance inside a capacitor that adds to its real behavior. A capacitor can hold its labelled capacitance and still have a high ESR, which is why a capacitance-only meter can miss a bad part.

The listings explain the method in the same way. They say the meter uses 100kHz so that the capacitor’s impedance, given as 1/(2πF·C), becomes small. With the capacitive part small, what is left is the series resistance. The listings also state the meter applies less than 15mV DC or peak to peak on a good capacitor, which is why it is described as suitable for in-circuit testing. Use cases named in the listings are repairs on TVs, LCDs and audio boards.

None of the listings states a CAT rating, and none describes mains testing. Treat the tool as a bench instrument for powered-down boards, and follow the manual for how to prepare a capacitor before measuring. The listings do not cover that step, so do not guess.

What matters when you choose a MESR-100

The measures change with this keyword. A general multimeter is judged on CAT ratings and counts. An ESR meter is judged on the low-resistance range and how clearly it shows tenths and thousandths of an ohm.

Measurement range and resolution

The top choice states 0.01R-100R in its title. The second states 0.000 to 100.0R and 0.001Ohm resolution at the 1 Ohm range. Good capacitors have very low ESR, so a resolution of 0.001Ohm matters more than a high top end. The other three give no range at all.

In-circuit use

The 15mV figure is the key. Four listings state it, and the second choice adds that you can check a capacitor without removing it. The first states “Auto Ranging in Circuit” in its highlight. For repair work on boards, in-circuit testing saves unsoldering.

Auto-ranging and display

The first and second state auto-ranging. The second adds a 4-digit display. The first lists the measurement type as LCR Meter and adds a printed ESR table for quick checks. The three remaining listings do not say how the reading is shown.

Power source

The second runs on 2 x AA batteries, not included, or a 5V Micro USB external supply. The listing’s power field says Corded Electric, which does not match the battery choice, so check before buying. The first is battery powered, the fourth battery powered, and the fifth lists Ac. The third lists no power source.

Listing completeness

Three of the five repeat the same theory bullets and little else. That is not a reason to avoid them, but you will be buying with fewer facts. Where a listing is silent, you will need the manual or the seller to confirm the range, accuracy and accessories.

MESR-100 listings that qualify

Five products fit. The cards show specs, pros and cons from each listing.

How each choice compares

Top choice: the one that names the V2 model

The title says MESR-100 V2 ESR Meter, Capacitor Tester/Low Ohm Meter 0.01R-100R. It is battery powered and weighs 8 ounces, and the listing describes a dual terminal for general capacitors or resistors and a printed ESR table. Auto-ranging and in-circuit use appear in the highlight, and the measurement type is LCR Meter.

If you were searching for mesr 100 v2, this is the only listing that says V2. The listing gives no resolution or accuracy figure and its bullets are short, including a bare line that reads “Wide Measurement Range”. Skip it if you need a stated accuracy.

Second choice: the most detailed specification

This listing states 100kHz testing, less than 15mV DC or peak to peak, a 4-digit display with 0.001Ohm resolution at the 1 Ohm range, and up to 1% accuracy over 0.000 to 100.0R. Power is 2 x AA batteries (not included) or a 5V Micro USB supply, and it includes a printed ESR table. It comes with test clips.

Its limits are the contradictory power field, Corded Electric against a battery choice, and the missing weight and size. Skip it if you want batteries supplied or a single clear power source.

Third choice: theory text, a 3.31 pounds weight and little else

The third listing repeats the 100kHz and 15mV explanation and says you can check TVs and LCDs in circuit. The specs list 3.31 pounds in weight and package dimensions of 0.39 x 0.39 x 0.39 inches, which do not fit together. Rely on neither number.

It also gives no range, resolution, accuracy, power source or included parts. Skip it unless you can confirm those with the seller.

Fourth choice: battery powered with UL listed

This one is battery powered and lists UL under specification met. Its bullets are the same theory text: 100kHz, 1/(2π·F·C), less than 15mV, in-circuit TV and audio board work. The title adds the word Set A in a name, and the listing states no range, no resolution and no accessories.

Because the listing does not say what ships, check whether test leads are included. Skip it if you need figures to compare against the first and second choices.

Fifth choice: handheld with an AC power field

The fifth listing calls the style Handheld and lists power as Ac. Its model number is the same as the third choice’s, 1005005533683632, so these two may be the same unit sold by different sellers. Its bullets repeat the theory text with one extra line that adds nothing about the device.

A power source labelled Ac needs a check against the manual, since the other listings describe batteries or USB. Skip it if you want clear power details.

Side-by-side comparison

Feature	First	Second	Third	Fourth	Fifth
Stated range	0.01R-100R	0.000 to 100.0R	Not stated	Not stated	Not stated
Resolution	Not stated	0.001Ohm at 1 Ohm range	Not stated	Not stated	Not stated
Accuracy	Not stated	Up to 1%	Not stated	Not stated	Not stated
Power	Battery powered	2 x AA or 5V Micro USB	Not stated	Battery powered	Ac
Weight	8 ounces	Not stated	3.31 pounds (unreliable)	Not stated	Not stated

Which one to choose

You want to compare readings against a datasheet. Choose the second. It is the only one with a resolution and an accuracy figure.

You want the model you searched for. Choose the first if you typed signstek mesr 100 v2 or just signstek mesr 100. Only that listing mentions the maker.

You are comfortable confirming details with the seller. The third, fourth and fifth are the same theory text with little else, so ask about range, power and accessories first.

For related reading, see the best MESR-100 V2 ESR meter, the best ESR meter, a capacitor meter and what a voltage meter does.

The listings give impedance as 1/(2π·F·C). With F = 100kHz = 100,000 Hz, 2π × 100,000 ≈ 628,319. Now take three possible capacitors.

• 1 µF = 0.000001 F. The product is 628,319 × 0.000001 = 0.628. So 1 ÷ 0.628 ≈ 1.59 Ω.
• 10 µF = 0.00001 F. The product is 6.283, so 1 ÷ 6.283 ≈ 0.159 Ω.
• 100 µF = 0.0001 F. The product is 62.83, so 1 ÷ 62.83 ≈ 0.0159 Ω.

Check the pattern: each tenfold increase in capacitance cuts the impedance tenfold, so 1.59, 0.159 and 0.0159 are consistent. Check one another way: 1.59 ÷ 10 = 0.159 and 0.159 ÷ 10 = 0.0159.

Compare with the second choice’s 0.001Ohm resolution at the 1 Ohm range. The 100 µF example gives about 0.0159 Ω of reactance, which is 15.9 times the 0.001Ohm step (0.0159 ÷ 0.001 = 15.9; check: 15.9 × 0.001 = 0.0159). That is why, for larger capacitors, the reactance becomes small enough that the series resistance dominates what the meter shows.

What this changes for buying: small values such as 1 µF still carry about 1.59 Ω of reactance at 100kHz, so for small capacitors the series resistance is a smaller part of the total. Check the manual for how the meter handles them, because the listings do not say.

Worked example: comparing the listed span

The top choice’s title states a 0.01R-100R span, which is 100 ohms minus 0.01 ohms, or 99.99 ohms of span. The second choice lists accuracy over 0.000 to 100.0R, so both listings end at 100 ohms. The upper limit therefore does not separate these two choices, and the difference has to come from the other listed features.

Common mistakes with a MESR-100

1. Buying on the name alone. Five listings share the same MESR-100 label but give very different detail. Compare range, power and accessories.
2. Trusting a contradictory field. The second choice lists Corded Electric next to battery power, and the third pairs 3.31 pounds with a 0.39-inch package. Confirm before relying on either.
3. Treating it as a mains tool. The listings describe board repair. None states a CAT rating, and mains circuits can kill. Panel work belongs to a licensed electrician.
4. Skipping the manual. The listings do not say how to prepare a capacitor for measurement. Read the manual first.
5. Expecting a verdict from one number. ESR tables and the maker’s limits decide whether a capacitor is good. The first and second choices both mention a printed ESR table.

For other bench instruments, see an ohm meter and a digital volt meter.

FAQ

What is a MESR-100?

It is a small meter listed for measuring a capacitor’s ESR, the series resistance inside it, in circuit. The listings describe 100kHz testing and use on TVs, LCDs and audio boards.

Is there a difference between the MESR-100 and the MESR-100 V2?

Only the first listing says V2. The others use the plain name. The listings do not explain any differences, so check with the seller if the version matters.

Can I test a capacitor without removing it?

Four listings say yes, because the test voltage is less than 15mV DC or peak to peak. The first lists in-circuit auto-ranging. Follow the manual for how to prepare the board.

What range should I look for?

The first states 0.01R-100R and the second 0.000 to 100.0R with 0.001Ohm resolution at 1 Ohm. The other three give no range.

How is it powered?

The first and fourth are listed as battery powered. The second lists 2 x AA batteries (not included) or a 5V Micro USB supply. The fifth lists Ac.

Is a CAT rating stated?

No. These are bench instruments for powered-down boards, so a CAT rating is not part of the listings.

Are the listings the same product?

Two share model number 1005005533683632, and four share nearly identical theory text. They may be the same design from different sellers, but the listings do not say. Ask before assuming.

Bottom line

Choose the second choice if you want numbers: range, resolution, accuracy and two power choices. Choose the first if you want the V2 name and a printed ESR table. Treat the other three as unconfirmed until the seller answers on range, power and accessories.

Sources

• Measurement category (Wikipedia): explains CAT classification and the 500 V to 12,000 V impulse withstand range, relevant to why a bench ESR meter with no stated CAT rating should not be used on mains circuits
• NOTE: The listings for this keyword carry little data beyond shared theory text, so this is the longest honest version without padding.