- on Test & Measurement
- Published in issue 11/2011 on page 58
Temperature Gradient Meter
Detect and report the tiniest changes
Sometimes it is not absolute temperature value that is of interest, but rather any small changes in that value. The circuit described here does not just measure these changes: it reports them both visibly and audibly. Using just a few active components it achieves a temperature resolution of just one tenthousandth of a degree.
Measuring temperature is a fairly simple task, but doing so precisely takes rather more skill, particularly when it is desired to obtain readings to a resolution of better than one tenth of a degree. The circuit presented here measures temperature to a resolution of one ten-thousandth of a degree, using just four active components and an optional display. The purpose of the circuit is to be able to detect even the smallest change in temperature: the emphasis is much more on extreme sensitivity and resolution than on absolute accuracy.
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Operating range: 0 °C to 40 °C
Absolute accuracy: approximately 2 °C uncalibrated
Resolution: in theory 4×10–5 °C, in practice approximately 3×10–4 °C; displayed resolution 10–4 °C
Range: degrees per 2 seconds to degrees per 100 minutes
Power supply: 6 V (four AA cells)