HEWLETT PACKARD (HP) 427A Multimeter (Side-Covers Removed)

Circa 1966

Designed to measure AC and DC voltages as well as resistance.

Use Cases:

A general-purpose lab instrument used for a wide range of electrical measurements before the advent of handheld digital multimeters.

• Voltage Measurement: It measures DC voltages from 1 mV to 1000 V and AC voltages from 0.3 mV to 300 V.

• Resistance: It functions as an ohmmeter for resistances from 0.2 Ω to 500 MΩ

• Field & Lab Use: Its battery-powered capability (optional) made it ideal for field work and for avoiding ground loops that occur with line-powered equipment.

• Audio & RF: Its AC frequency response ranges from 10 Hz to 1 MHz, making it suitable for audio and some radio frequency applications.

Historical Significance:

• Solid-State Transition: It was one of the first HP meters to fully utilize solid-state components (transistors), providing much greater ruggedness and reliability than previous tube models.

• Portability: At only 5.5 lbs and equipped with a carrying handle, it set an early standard for high-accuracy portable test equipment.

• Design Integrity: It is celebrated by collectors and engineers for its high-quality construction, including a large, mirrored analog scale for precise, parallax-free readings.

(H-16.5cm x W-13cm x D-20cm)