The Model 503 Milliohmmeter permits rapid, accurate, low resistance tests. It combines a ruggedness and ease of operation not possible with bridges. Measurements are read directly on a mirror scale meter. Balancing is unnecessary, calibration stability is excellent, and the instrument is not damaged by overload. Features include: 13 full-scale ranges from 0.001 to 1000 ohms; accuracy of ±1% of full-scale meter indication and ±0.5% of full-scale output voltage; no zero drift; rise time of 0.25 second to 90% of final value; sample dissipation of less than 10 microwatts; 100-millivolt dc output for chart recordings or control functions; and front panel calibration. The measurement technique involves an ammeter-voltmeter method using an ac test current. Typical uses include measurements of internal resistance of dry cells, resistivity profiles of thermo-electric materials; measurements of temperatures with thermistors; dry-circuit testing of contacts, and safe measurement of fuses and squibs.