Temperature measurement
First Claim
1. A temperature measuring system comprising a temperature sensing element delivering a signal voltage representative of temperature, a reference voltage source, a transformer, switches controlling the application of said signal voltage and the reference voltage to a primary winding of the transformer, a digital processing unit, an analogue-to- digital converter converting signal voltages appearing on a secondary winding of the transformer to digital signals and applying them to said digital processing unit, and a switch control channel whereby said switches are controlled by periodic outputs from the digital processing unit, said control channel including transducers that electrically isolate the switches from the digital processing unit.
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Abstract
In a temperature measurement region, a thermocouple and a reference voltage source in turn supply voltages via solid state switches to the center-tapped primary winding of a transformer. The output voltages of the transformer secondary winding are applied via an analogue-to-digital converter to a crystal-clock-regulated digital processing unit that obtains the difference of positive and negative voltages derived from the thermocouple signal, the positive and negative voltages derived from the reference voltage, for subsequent ratiometric processing. The switches are operated by a switch control unit that responds to signals arriving via electrically-isolating transducers from switch control latches that receive switch control outputs from the digital processing unit.
26 Citations
6 Claims
- 1. A temperature measuring system comprising a temperature sensing element delivering a signal voltage representative of temperature, a reference voltage source, a transformer, switches controlling the application of said signal voltage and the reference voltage to a primary winding of the transformer, a digital processing unit, an analogue-to- digital converter converting signal voltages appearing on a secondary winding of the transformer to digital signals and applying them to said digital processing unit, and a switch control channel whereby said switches are controlled by periodic outputs from the digital processing unit, said control channel including transducers that electrically isolate the switches from the digital processing unit.
Specification