Hand-cranked insulation resistance tester (“Megger”-type), portable electrical test instrument. Calibrated in megohms (MΩ) with a 500-volt test output, generated by the built-in hand-driven generator. Instruments of this type were used by electricians and engineers to test the insulation resistance of wiring, cables, motors, and electrical installations to ensure safety and detect faults. Compact bakelite-cased field instrument typical of professional electrical maintenance equipment. Mid-20th century, c.1940s–1960s.
,%20portable%20electrical%20test%20instrument.%20Calibrated%20in%20megohms%20(M%CE%A9)%20with%20a...){kind=link}