15v on protoboard reads 30v on multimeter - how do I correct this?

[dcasey3]

When i use the mydaq to read the voltage from the -15v, +15v ports on my protoboard, the reading is over 29v. If i measure the battery or 5v ports, the reading comes out correctly. Am I doing something wrong?

[Henrik_Volkers]

You should read 30V if you measure between -15V and +15V 🙂

If you measure between AGND and +/- 15V you should read +/- 15V.