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Topic: Adding thermometer feature to a regular digital multimeter (Read 1142 times) previous topic - next topic

Adding thermometer feature to a regular digital multimeter

Hi guys,
I recently added the thermometer feature to my digital multimeter using an analog temperature sensor (TMP35) and a couple of resistors. The technique is very simple. The TMP35 provides a linear output voltage proportional to the Centigrade temperature. The scale factor is 10mV per degree C. The sensor output is divided by 10 using a resistor divider network and is fed to the input terminals of the multimeter which is set to measure voltage between 0-200 mV. The meter displays temperature in degree Celsius.
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Although this sounds pretty straight forward, there are some issues that should be taken care of to make this technique work. For instance the reference voltage of the multimeter's A/D converter and the sensor's ground terminal are at different potential when you power both of these with the same battery. You will find details on this here.
http://embedded-lab.com/blog/?p=4951

Thanks,