Instead of using an expensive logger, I'd like to measure and log temperature using a PC microphone port.

I'm going to use TMP36 Temperature Sensor. The output voltage of the sensor is measured by the mic port. The voltage is supplied from a USB port.

Here is the diagram.

enter image description here

But here are my concerns:

  1. the mic port might have a certain range of voltage it can measure
  2. the accuracy of voltage the port can measure might be impractical
  3. Windows might not have the feature to measure the voltage directly

Is it possible?

EDIT 2018-02-14 9:36

My huge misunderstanding was the mic port can measure any kind of voltage generated by a mic to detect sound. Here are what I learned from the comments and answers.

  • The mic port will likely be AC-coupled (i.e. for AC signals only)
  • There might be other obstacles (e.g. low frequency cut)
  • So what I planned is hardly feasible
  • To measure voltage by a mic port, you need to build a certain circuit or use a frequency converter
  • It might be better to take other options such as Arduino Nano clones(~$3.50 on eBay)
  • 1
    \$\begingroup\$ The mic port will likely be AC-coupled, also the sound card is trying to provide a voltage to power the mic. \$\endgroup\$ – user253751 Feb 14 '18 at 3:28
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    \$\begingroup\$ You are mixing apples and oranges. The mic port is for AC signals only. Frequencies below 20 HZ are filtered out. Not sure how you were going to 'measure' the temperature on your PC anyways. You can look into voltage to frequency converters. \$\endgroup\$ – Sparky256 Feb 14 '18 at 3:29
  • \$\begingroup\$ Is there any reason you don't want to use an Arduino or equivalent and then send that to a PC via serial? \$\endgroup\$ – jramsay42 Feb 14 '18 at 3:31
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    \$\begingroup\$ test in audacity and verify DC offset . some are DC balanced , others ac coupled . we dont know. aux in may be best \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 14 '18 at 3:38
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    \$\begingroup\$ "Instead of using an expensive logger..." - Arduino Nano clones with built-in serial-USB sell for ~$3.50 on eBay, including USB cable and shipping! \$\endgroup\$ – Bruce Abbott Feb 14 '18 at 6:31

If you want to read a TMP36 using a microphone port you'll most likely need to convert the signal to AC.


simulate this circuit – Schematic created using CircuitLab

This circuit chops the TMP36 output, producing an AC signal whose amplitude depends on the voltage output from the TMP36.

Changing the value of R3 to 1K will increase the amplitude of the signal to a range better suited to AUX ports.


I would recommend using a voltage to frequency converter. The soundcard input is AC-coupled, so it can't measure DC, but is good for frequency measurement (that what it is mainly designed for). Just google "voltage to frequency converter" and you will find many chips that can do this task.


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