I/O current or voltage check with switching matrix

[Vincent90]

Hi all,

I want to use a switching matrix to test current and voltage terminals of an electrical cabinet. For this I have an injector voltage, injector current, a voltage measurement and current measurement from one side of the matrix (line side) and a 20 rows for I / O test. Is there a way to check (through a hardware or software solution) that we are willing to test a voltage or current in automatic mode.
The ideal would be to have a keyed physical indicating that we test the right card but if the operator uses the wrong card, I would check that is not injected +-24V on a 0-20mA input current card input.

I wish you will illuminate me !

Best Regards,

Vincent

[johnsold · Accepted solution]

Vincent,

Some approaches for you  to consider:

1. Add a resistor or a few resistors to each card.  Measure the resistance before applying any power to the I/O lines.  Code the resistance(s) to identify the class of board (Current or Voltage) and range (if applicable).  Simple jumpers on unused pins of the connector may also be used.

2. Measure the input impedance (or at least the resistive component) before applying power.  A Voltage input device probably has a high input impedance while the Current input device has a low input impedance. This could detect and reject some devices with incorrect input resistors installed.

3. Use a camera to determine which device is connected.  (This should satisfy your request to be illuminated!)

4. You could replace the operator with a robot, but the robot would still need to use something like 1, 2, or 3 to identify the  boards.

5. Use physically incompatible connectors/card edge congfigurations so that the board cannobe plugged in to the wrong tester.

Lynn

[Vincent90]

Thank you so much for your fast reply.

I am going to add resistor measurement to each connector.

Do you know what does the difference is between a switching matrix one wire and two or four wires ?

For instance, the NI PXI-2531 gets a 8*64 switching matrix (1 wire) and a 8*32 switching matrix (2 wire).

[johnsold]

Look at the NI Switches Help document.  In the N-Wire Switching Modes page it describes the differences among 1-, 2-, and 4-wire modes.  2-wire basically switches pairs of relays simultaneously.  This is useful for differential channels.

Lynn