The Keithley 179A is a 4½-digit True RMS digital multimeter engineered for precision measurement across DC voltage, AC voltage, DC current, AC current, and resistance. Built for laboratory and field deployment, it delivers waveform-insensitive AC measurements via TRMS technology and spans measurement ranges from 1 µV to 1000 V for voltage and 1 mΩ to 220 MΩ for resistance.
## Technical Specifications
**Display & Interface**
• 4½-digit LCD with backlight; 0.45-inch digit height
• Polarity, function, range, and status indication
• Overrange display: “OL”
• Conversion rate: 3 readings/second
**Voltage Measurement**
• DC: 200 mV to 1200 V (5 ranges); ±0.04% accuracy; 10 MΩ input impedance; 1 µV resolution
• AC (TRMS): Up to 100 kHz; ±(0.07% of reading + 2 counts); 3:1 crest factor; 2-second settling time
**Current Measurement**
• DC: 200 µA to 20 A (6 ranges); ±0.02% accuracy (up to 2 A); ±0.5% at 20 A; 1 nA resolution
• AC (TRMS): Up to 15 A continuous, 20 A periodic; ±(0.07% of reading + 2 counts); 3:1 crest factor; 2-second settling time
**Resistance**
• Range: 1 mΩ to 220 MΩ (11 decades)
• Accuracy: ±(0.01% of reading + 2 counts) on 200 Ω range
• HI/LO Ohms modes: HI provides 2 V compliance for semiconductor activation; LO offers 200 mV compliance for in-circuit testing
• 1 kV protection on Ω input
**Performance**
• Warm-up time: 1 hour to rated accuracy
• Temperature coefficient: ±(0.01% of reading + 0.2 digits)/°C
## Key Features
• Front-panel push-button range and function selection with automatic polarity
• 100-reading data storage with selectable rates from 3 readings/second to 1 reading/hour, plus manual trigger
• Continuous min/max recording
• Dual resistance modes for semiconductor and in-circuit applications
## Typical Applications
General-purpose electronics testing, troubleshooting, laboratory measurement, and field diagnostics where TRMS AC accuracy on non-sinusoidal waveforms is required.
