Fri Apr 25, 2008 5:30 am
A thermcouple type probe carries a voltage back to some conditioning circuitry, while an RTD or thermistor type probe represents temperature change with resistance change. This is usually biased by a voltage or forms part of a voltage divider and carried back to the conditioning / measuring circuitry (wheatstone bridge, op-amp, A/D, etc.) and generally need to be calibrated as a system.
A "digital probe" contains a sensing element, conditioning circuitry, A/D conversion, and some sort of micro or simple state machine logic to be able to transport this digitized representation in a serial fashion, all within the probe element. Additionally, they can contain serialization data, which means an individual probe can be identified no matter where in the system it is plugged in so that any calibration data, if needed, can be applied on a per probe basis. Some even have non-volatile memory right in the probe to store cal data there - once again, right in the probe itself. Digital transport of the temp data means no interference from external electrical noise and no worries about probe interconnects changing resistance due to corrosion, moisture, etc.
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