simulating hall effect sensor

[VTChris]

I am developing a HIL system with LabVIEW, and using a PXI-6713 analog output card to simulate the output of some 2-wire Hall effect wheel speed sensors.  The manufacturer of these sensors doesn't give a whole lot of information:

http://www.bendixvrc.com/itemDisplay.asp?documentID=2685

I have 8 sensors to simulate, so one sensor per channel on the AO card;  I have to connect them as single-ended.

I tried sending just an AC triangle wave on one of the wires, but the receiver did not detect a wheel speed.  I tried this with the other lead to the sensor connected to AO_GND, and also connected to the same AO pin as the first, but with a 2k resistor between them.  None of these scenarios produced a valid signal as far as the receiver is concerned.

After failing to get results, I made some more measurements, and found that the receiver that these sensors normally plug into has 5VDC across each sensor terminal pair when a sensor is not connected.  So now I'm also not sure about connecting an AO to the 5V on the controller terminal;  hope that wasn't a bad idea.

I'm wondering if I need to use something like a differential op amp to change the AO output from single ended to differential.

Anyone else have some better ideas?

[Henrik_Volkers]

Maybe your DUT can detect that there is no current sink attached, you might need to add a resistor of 1k-2k in parallel.

 Take a look into the Spec of your 6713 and check if it can drive 1k-2k Ohm at its output.

However this should have been noted the HIL-Test spec 😉 and be a part of the test (broken wire).

For a more realistic simulation  you should pick up the phone and ask the sensor manufactor for simulation model (shematic).

[VTChris]

Thanks for the reply.

I had already checked if I was in an over-current situation.  But the 6713 can source up to 5mA; with the 2k resistor I used as a load, that gives up to 10V, so I am fine in that respect.

The manufacturer has been less than cooperative.  I stripped the insulation off of one of the sensors, and tried to capture the waveform while the sensor was in use.  The non-isolated ground of my scope caused the sensor to fail.  I'm going to try to simulate the sensor with a differential op-amp because I believe I need an isolate differential signal.

[rtj_fl]

Did you ever get this working?