One possible problem when using the Dual-Channel Amplifier of the Current and Voltage System is that you always have to plug in the Channel 1 cable. If you do not, the amplifier circuitry of the Dual-Channel Amplifier does not get power and the readings will be way off.

A good rule is: Always plug both the the cables coming out of the Dual-Channel amplifier box, even if you are only using one probe plugged into it.