MESR-100 ESR Capacitor Meter – In-Circuit Resistance Tester
MESR-100 ESR Capacitor Meter – In-Circuit Resistance Tester
MESR-100 Professional ESR & Low Ohm Capacitor Meter
The MESR-100 is a precision auto-ranging capacitor ESR (Equivalent Series Resistance) and low-ohm meter designed for electronics technicians, hobbyists, and repair professionals. Using a true 100 kHz sine wave measurement method — identical to capacitor manufacturer testing standards — this compact tester lets you accurately evaluate capacitor condition while components remain in-circuit, saving you hours of desoldering work.
Whether you're servicing TVs, LCD monitors, audio amplifiers, or other circuit boards, the MESR-100 tells you instantly whether a capacitor is good or degraded — without removing it from the board.
Made in Mainland China.
Why ESR Testing Matters
A capacitor can test at its correct capacitance value yet still be faulty — a high internal series resistance (ESR) is the real culprit in most capacitor failures. The MESR-100 targets exactly this: it applies less than 15 mV DC (peak-to-peak) across the component, keeping voltage low enough for safe in-circuit measurement while still delivering a highly accurate ESR reading.
Key Features
- Auto-Ranging: Automatically selects the best measurement range from 0.001 Ω to 100.0 Ω — no manual range switching needed.
- True 100 kHz Sine Wave: Cancels capacitive reactance so you measure only the true series resistance value.
- In-Circuit Testing: Apply less than 15 mV peak-to-peak — safe for components still mounted on the board.
- 4-Digit LCD Display: High-resolution 0.001 Ω readout at the 1 Ω range for precise results.
- Dual Test Clips Included: Spring-loaded clips for fast, hands-free component contact.
- Built-In Reference Table: Printed ESR chart on the meter body for instant pass/fail comparison.
- Dual Power Options: 5V Micro-USB or 2 × AA batteries (not included) for bench or field use.
- Long Battery Life: Over 80 hours on a set of AA batteries.
- Compact & Lightweight: Just 139.6 g — easy to handle during board-level diagnostics.
Measurement Ranges & Accuracy
| Range | Accuracy | Refresh Time |
|---|---|---|
| 0.000 – 1.000 Ω | 1% + 2 Digit | ~0.4 s |
| 1.000 – 10.00 Ω | 1% + 1 Digit | ~0.4 s |
| 10.00 – 100.0 Ω | 2% + 1 Digit | ~0.4 s |
Auto mode: 0–2 seconds (longer for higher capacitance values). Accuracy verified after zeroing with 1 Ω, 10 Ω, and 100 Ω reference resistors.
Full Specifications
- Color: Black
- Measurement Range: 0.001 Ω – 100.0 Ω (ESR / Internal Resistance)
- Minimum Capacitance: >1 µF
- Resolution: 4 digits / 0.001 Ω at 1 Ω range
- Test Frequency: 100 kHz sine wave
- Test Voltage: <15 mV DC peak-to-peak
- Power: 5V Micro-USB OR 2 × AA 1.5V batteries (not included)
- Operating Current: 0.02 A
- Battery Life: >80 hours
- Item Dimensions: 14.5 × 8 × 3 cm (5.7 × 3.1 × 1.2 in)
- Item Weight: ~139.6 g (4.9 oz)
- Package Dimensions: 17 × 9 × 5 cm (6.7 × 3.5 × 2.0 in)
- Package Weight: ~218 g (7.7 oz)
What's in the Box
- 1 × MESR-100 Capacitor ESR Meter
- 2 × Test Clips
- 1 × User Manual
- Batteries and USB cable not included
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Frequently Asked Questions
Q: What exactly does the MESR-100 measure — capacitance or ESR?
A: The MESR-100 measures ESR (Equivalent Series Resistance) — the internal series resistance of a capacitor — not its capacitance value. A capacitor can have the correct capacitance yet still fail due to elevated ESR, making this meter an essential tool for diagnosing faulty capacitors in circuit boards.
Q: Can I test capacitors while they are still soldered onto the circuit board?
A: Yes. The MESR-100 applies less than 15 mV DC peak-to-peak during testing, which is low enough to safely perform in-circuit measurements on most capacitors without desoldering them. Always ensure the board is fully powered off and discharged before testing.
Q: What power sources does the MESR-100 support?
A: The meter supports two power options: 2 × AA 1.5V batteries (not included, providing over 80 hours of use) or a 5V Micro-USB connection for continuous bench use. This makes it flexible for both workshop and field repair scenarios.
Q: What is the minimum capacitor size I can test with this meter?
A: The MESR-100 is designed to test capacitors with a capacitance value greater than 1 µF. Very small capacitors (below 1 µF) may not provide reliable ESR readings with this instrument.
Q: How accurate is the MESR-100 and how do I ensure best results?
A: Accuracy reaches up to 1% in the lower ranges after proper zeroing. Before use, always zero the meter with the test clips shorted together, then verify with known 1 Ω, 10 Ω, and 100 Ω reference resistors. The built-in printed ESR reference table on the unit body helps you quickly determine whether a measured value is within an acceptable range for a given capacitor type.
Production & Packaging Notice
To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.