A multimeter is the tool you reach for first — before the oscilloscope, before the logic analyzer. Voltage, resistance, continuity, current, capacitance, diode testing. A good one is accurate, safe, and fast. The used market is full of ex-industrial Fluke meters that will outlast you.
Multimeter accuracy is specified as ±(% of reading + number of counts). More 'counts' = more digits of resolution. 4000 counts: 0.000-3.999V on the 4V range. Fine for general use. 6000 counts: The current standard (Fluke 117). 20000+ counts: Precision work, 4-20mA loops, battery testing. The difference between 12.6V and 12.63V matters when diagnosing a charging system.
CAT I: Protected electronics. CAT II: Single-phase outlets, appliances. CAT III: Three-phase distribution, breaker panels. CAT IV: Utility connection, outdoor feeders. For mains work, CAT III 600V minimum. The safety rating isn't marketing — it's the difference between a meter that survives a voltage transient and one that explodes in your hand. Cheap meters lie about CAT ratings.
True RMS meters accurately measure non-sinusoidal waveforms (VFD outputs, dimmer circuits, switching supplies). Average-responding meters (cheaper) assume a pure sine wave and can be 30-40% off on distorted signals. Worth the small premium — most modern electronics work involves non-sinusoidal signals.
Auto-ranging: Don't buy a manual-range meter in 2026. Continuity beeper (fast latch): Instant beep when probes touch — slow beepers are infuriating. Min/Max/Average: Captures transients. Backlight: Essential for panel work. Magnetic hanger: Underrated feature. LoZ (low impedance): Ghost voltage detection.
Budget ($30-80 used): Fluke 15B+, Brymen BM235 (EEVblog), Uni-T UT61E. Good feature set, questionable CAT ratings on some.
Pro Standard ($100-250 used): Fluke 87V (the bench standard), Fluke 179, Agilent/Keysight U1272A. Lifetime meters. Buy once.
Precision ($300+): Fluke 287/289 (data logging), Keysight 34461A bench meter. Lab-grade accuracy.
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