Introduced in 1983; see HP Journal of February 1983.

The 3478A multimeter is a low-cost HP-IB (IEEE 488) programmable instrument for system measurements. A compan ion product to the 3468A with similar display and measurement features, the microprocessor-based 3478A is an autoranging, 5 1/2-to-3 1/2-digit, five-function digital multimeter […]

This model also has a lot in common with the 3457A (similar calibration data, LCD protocol, etc).

• Ranges : 30mV to 300V
• Sensitivity: 100nV
• Basic accuracy: +-(0.0034% reading + 2 counts)
• Input resistance : 10GΩ (?!) on ranges up to 3V; 10MΩ +- 1% on 30V and 300V ranges

• 300kHz true RMS
• Ranges: 300mV to 300V
• Input impedance: 1MΩ shunted by < 60pF

• Ranges: 30Ω to 30MΩ
• Sensitivity: 100 μΩ
• Open-circuit voltage: 6.5V

• Ranges: 300mA, 3A
• Burden voltage : 0.1V / 1V

• Ranges: 300mA, 3A
• Burden voltage : 0.1V / 1V

The 3478A contains one main CPU (Intel i8039) and one CPU in the analog domain (i8049).

• Main CPU ROM dump, datecode 118?
• Analog CPU ROM dump

• replacement LED display & protocol analysis
• some info on Calibration RAM contents
• firmware patch adding a relative mode

• Python driver for remote communication over GPIB as part of PyMeasure
• Another python driver which also supports reading/writing the cal memory
• Sophisticated control software which also supports editing the calibration data, but only works with Prologix compatible USB-to-GPIB adapters