1941-01-01

An Instrument for Continuous Measurement of PISTON TEMPERATURES 410084

THE problem of developing an instrument for the continuous measurement of piston temperatures by the thermocouple method can be divided into three parts: 1. The measuring instrument or instruments necessary; 2. The installation of the thermocouples in the piston; 3. The necessary electrical circuit connecting the two.
After reviewing the principle of operation of the potentiometer method of reading temperatures, the authors describe the standard light-beam galvanometer selected for use with the intermittent contacts. The sensitivity of the galvanometer, they explain, is controlled by means of a variable-ballast resistor connected across its terminals. A multiple switch makes possible the continuous measurement of one temperature or the intermittent measurement of several temperatures.
Test data obtained with the instrument presented in this paper include temperature gradients of both aluminum and cast-iron pistons; the effect of load variation on piston temperatures; and the effect of spark advance on piston temperature.
They announce that a production engine fitted with the final design of the instrument has been run 25,000 miles at 60 mph on a dynamometer with no attention or adjustments, and that a test-car installation has shown that measurements can be made continuously on the road.

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