open collector acquisition of open collector output data

[Rakesh Kumar]

the output data that comes from a single wire from the instrument without the ground signal from the instrument , ie , the open collector output data. which is the cheapest and the best NI hardware to acquire open collector output data ?

[Rolf Kalbermatter]

the output data that comes from a single wire from the instrument without the ground signal from the instrument , ie , the open collector output data. which is the cheapest and the best NI hardware to acquire open collector output data ?

You will need some ground reference somehow (so two wires at least) and also some biasing of the signal with a resistor to pull it to the passive level. Otherwise you can't measure an open collector signal properly. The cheapest will most likely be one of the USB DAQ boxes.