description Heathkit IM-28 Overview
The Heathkit IM-28 is a solid-state electronic voltmeter sold by Heathkit in kit form. Its high input impedance was intended to reduce the loading effect that a measuring instrument can impose on the circuit under test, an important consideration when working with electronic equipment. The unit belongs to Heathkit's line of hobbyist and service instruments and is relevant to collectors, restorers, and electronics enthusiasts interested in building or using vintage bench test equipment. It was designed for practical voltage measurements during circuit work.
help Heathkit IM-28 FAQ
What is a Heathkit IM-28?
The IM-28 is a Heathkit solid-state vacuum-tube voltmeter, or VTVM, sold as an electronic test instrument. It was supplied in kit form and intended for bench work such as checking voltages, resistance, and electronic circuits.
Why does the Heathkit IM-28 have high input impedance?
The IM-28's approximately 11-megohm DC input reduces the loading effect on the circuit being measured. That matters when testing high-resistance or sensitive vintage electronic circuits.
What can the Heathkit IM-28 measure?
Its published ranges include voltage and resistance measurements, with resistance coverage extending from about 1 ohm to 1,000 megohms. The exact usable range depends on the instrument's condition, probes, and calibration.
Is the Heathkit IM-28 a modern digital multimeter?
No. It is an analog VTVM from the Heathkit era, so it uses a moving meter and requires more care with warm-up and calibration than a modern digital multimeter. Its value today is mainly in vintage repair, restoration, and period-correct test work.
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