RECORDING RAPITJLY CHANGING CYLINDER-WALL TEMPERATURES

The present report deals with the design and testing of a measuring plug suggested by H. Pfriem for recording quasi-stationary cylinder wall temperatures. The new de-vice is a resistance thermometer, the temperature-suscep-tible part of which consists of a gold coating applied by evaporation under high vacuum and electrolytically strengthened. This resistance layer, being located on the surface of the wall, enables an immediate surface temperature reading not obtainable heretofore with the conventional ” thermocouples. Its inertia is negligible. The uncertain and tedious conversion of the test data to the surface is eliminated. A further advantage over the thermocouple lies in the much higher current fluctuations which permit the charting of the temperature curve with-out amplification. The new method combines substantially higher instrumental accuracy with a maximum of simplicity in,operation. Eventual correction of test data is greatly simplified by the laminated structure of the measuring plug. After overcoming initial difficulties, calibration of plugs u’p to and beyond 400 ° c was possible. The meas-urements were made on high-speed internal combustion en-gines. ‘. The increasing effect of the carbon deposit at.the wall surf-ace with increasing operating period iS indicated by means of charts. *ltMessung schnellver~nderlicher Zylinderw’a’ndt’emp’e”ratUren.