Dear All,
I am trying to use analog inputs of 6025E in differential mode to measure the voltage across a high power LED driven by an external circuit . The anode is connected to +Vcc (24V) and Cathode is sunk in to a MOS gate of the external circuit. I have made a potential divider of 100K/10K across the LED and I am feeding the 2 ends of the 10K to two AI inputs (AI0 & AI8). If I remove the 2 wires from the card, the circuit works even in presence of the potential divider. As soon as I connect the wires, the 6025E analog inputs provides a leakage path, sinks the cathode and the LED glows when it is supposed to be off.
The manual says that the input impedance is >10G ohms. So this should not have happened. Should I have connected the 100K bias resistors (+ve of AI0/AI8 to AIGnd) while using the differential mode ? How will this eliminate the leakage path ?
