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Incorrect voltage reading

1050 Views - Created 14/08/2020


Posted by:

jevers99 Avatar


We're having problems when trying to read two voltages, on different channels at the same time on our ADC Pi. We have a voltage divider set up and can verify that when reading one channel at a time, the voltage is correct. When we attempt to read off two channels we've seen three different things

1) No voltage on the second channel but normal on the first

2) A higher voltage on the first channel and nothing on the second

3) Both channels reporting a voltage but one or both possibly incorrect.

We are using the appropriate voltage multiplier.

Kind regards,



Posted by:

andrew Avatar

United Kingdom

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Hi Jon

The ADC Pi contains an onboard voltage divider on each channel so adding an additional voltage divider on the inputs can cause it to show an incorrect voltage. You can increase the voltage range by adding a single resistor in series with the input. We have a calculator that you can use to get the correct resistor value for your desired voltage range.

If the voltage still does not read correctly after making the above changes can you try reading on channels 5 to 8 and see if they have the same problem? Channels 1 to 4 and 5 to 8 are on two different ADC chips so if the voltages read correctly on one chip but not the other that would indicate that one of the ADCs is faulty.

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