AN AUTOMATIC GUARD-RING TEMPERATURE CONTROLLER FOR THERMAL-CONDUCTIVITY MEASUREMENTS
Abstract
An automatic controller is described, which maintains the guard ring at the same temperature as the hot plate in an apparatus formeasuring thermal conductivity. Control is maintained in response to the signal from a 6-power thermopile, which actuates a commercialelectronic null detector. The output of the null detector drives a commercial magnetic amplifier. Proportional control is obtained bysuperposing an oscillating signal, generated by a Wien-bridge oscillator, on the control signal, so that the control relay continuallyopens and closes with a period of about 5 seconds. An increase in the demand for power causes the "closed" intervals to become longerand the "open" intervals to become shorter. Opening or closing of the relay changes the power input by only about 2 percent whenconditions suitable for making measurements exist. Temperature control to within + 2 mdeg C can be achieved under favorable conditions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1962
- Accession Number
- AD0291096
Entities
People
- Alan H. Woodcock
- Francis W. Botsch
- Michael J. Sacco