LCR / ESR / Component Tester
Test Instrument
Measures what a multimeter can't: inductance, real capacitance at frequency, and ESR — the equivalent series resistance that reveals a worn-out electrolytic even when its µF still reads fine. The repair bench's lie detector.
What it looks like
LCR / ESR / Component Tester
A typical test instrument — exact shape, colour and markings vary between manufacturers.
Types & variants
Key specs
Parameters
—L, C, R, plus ESR, dissipation factor (D), quality factor (Q), impedance (Z) and phase angle θ.
Test frequency
Hz–kHz100 Hz/120 Hz/1 kHz/10 kHz/100 kHz. Electrolytics are specified at 100/120 Hz, ceramics and inductors at 1 kHz+; values genuinely differ with frequency.
Basic accuracy
%0.1–0.5% bench, 1–2% handheld — fine for sorting and repair.
Range
—Good meters span pF to tens of mF and nH to kH. Check the extremes you need (big electrolytics, tiny RF inductors).
In-circuit ESR
—ESR meters test below 0.1 V so semiconductor junctions don't conduct — allowing capacitor checks without desoldering.
Markings
4-wire Kelvin clips or a multi-pin ZIF socket (component testers). Auto-detect testers show the part type, pinout, and measured values on screen.
Standard values
TC1/LCR-T4 auto testers (identify + measure almost any 2/3-pin part), MESR-100 ESR meter, UNI-T UT603/612 handhelds, DE-5000 as the respected budget LCR, GW Instek bench units in labs.
How to choose
1) Repair-focused: prioritise ESR + in-circuit ability — bad ESR is the #1 electrolytic failure signature. 2) Design-focused: bench LCR with multiple frequencies and D/Q readouts for magnetics work. 3) Every bench deserves a ₹500 auto component tester — it identifies mystery transistors, pinouts and gain in seconds. 4) DISCHARGE capacitors before testing; a charged cap kills these meters.
Pinout & package
Kelvin (4-wire) connections eliminate lead resistance for milliohm-level ESR readings. ZIF socket testers: insert any leaded part in any orientation, press test.
Example circuits
- Sweeping a monitor PSU's electrolytics in-circuit for the one with 5 Ω ESR causing the no-start
- Sorting a drawer of salvaged inductors by actual µH
- Matching capacitor pairs for a filter design
- Identifying an unmarked SOT-23 as NPN with hFE 320 via the auto tester
Common failures
Blown input from charged capacitors (the classic killer), oxidised ZIF sockets (erratic IDs), and drifting calibration. Component testers misidentify exotic parts (MOSFETs with internal diodes, TRIACs) — trust but verify.
How to test
Verify against known-good 1% parts: a 100 nF film cap, 100 µH inductor, 10 Ω resistor. Short the Kelvin clips and zero/relative-out the residual. ESR sanity: a new 1000 µF/25 V should read well under 0.1 Ω.
Substitutes
A DMM's capacitance range covers rough µF checks (no ESR). A scope + function generator measures L and C via resonance or RC/RL time constants — the classic lab method. Nothing cheap substitutes for in-circuit ESR in repair work.