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1945 - a foursome George Andrews, Leo Douville, Harold Horner and Herman Roemer devised a new circuit tester for communications


CD 1966044 E&MP29.009

Electric Machinery

January 15, 1945

To four young tool engineers in the electrical group at The Glenn L. Martin Company, Baltimore, Maryland, goes credit for devising a new tester for communications systems in Martin electric turrets.

Already installed at several locations in the company's plants, the new device - an unbalanced electronic bridge circuit - has resulted in a saving of 600 per cent of the time originally used for this testing work.

Most difficult of the problems faced by the engineering quartet, George Andrews, Leo Douville, Harold Horner and Herman Roemer, was to evolve a device which would remain consistent while testing circuits. This was necessary in order to permit acceptance only of parts which met manufacturing specifications. Also the wiring problem, due to leakage in the tester, was a complicated one.

The new circuit tester meets such exacting requirements as the insulation test of 100 meg-ohms at 600 volts and .01 resistance for all circuits. As to the leakage, an unbalance is set up when circuits are insulated at less than 100 megs and causes a relay to operate, automatically lighting an indicator signal. This light has to be released before tests can continue on other circuits.

Continuity of circuits is checked by passing approximately three amperes through each circuit and measuring the voltage drop as indicated on a meter. An open circuit is indicated by unbalancing the bridge and causing the red light to glow. An acceptable circuit is indicated on a calibrated meter.  

Original Caption by Science Service
Glen L. Martin Company

National Museum of American History


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