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Azur Electronics
The HP 3478A is a versatile multimeter with dc and ac rms volts, dc and ac rms currents, 2 & 4 wire resistance measurement. The reading can be displayed in 5½, 4½, or 3½ digits. Features auto-ranging, auto-zero, HP-IB remote programming and electronic calibration. The Operation, Calibration and Service Manual was downloaded. The HP 3478A cost $1,295 in 1993.
The push-button switch by the 4mm sockets selects front or rear inputs.
Top view with cover removed
Bottom view with cover removed
Specification
dc Voltage: 30mV, 300mV, 3V, 30V, 300V ranges.
ac Voltage: 300mV, 3V, 30V, 300V (true rms) ranges.
Resistance: 30Ω, 300Ω, 3kΩ, 30kΩ, 300kΩ, 3MΩ, 30MΩ (2 or 4 wire) ranges.
dc Current: 300mA, 3A ranges.
ac Current: 300mA, 3A (true rms) ranges.
April 2007
Just needed a clean-up and powered-up with 'Self Test OK' displayed.
Unusually for HP, the line frequency 50Hz/60Hz is set by the left hand switch of the Rear Panel DIP Switch, set to '1' (Up) for 50Hz. Also the line voltage is set by the grey wire, next to the power transformer, set to the appropriate pin.
I use the 3478A when I need to check readings on my other multimeters or require extra accuracy. As it has a LCD display it can be difficult to read in low light situations. Apart from this it is an excellent multimeter.