status of field point modules

[ltok]

I would like to know how to detect the status of the channels of some of the field point modules.

For example, for RTD-124, if there is no device connected to a channel or the device connected is broken, it will gives a "Open RTD Detected" when using FP Read.vi. What about for AI-110, AO-200, DI-304, DO-403.

For AO-200, there are two range settings possible for the channels of this module. (i) When set to reading range of 0.0035 to 0.021 amps, it will gives “Open current loop” if there is nothing connected to a particular channel. But, (ii) when reading range set to 0 to 0.021 amps, the status shows always success even when it is not connected. Correct me if I am wrong. Is there any other way of detecting the connection status of AI-110 and other modules??

Thank you & Regards

Lee

[Wayne.C]

lee,

The RTD-124 can provide status because a RTD sensor has an expected range of resistance.  Module can then make the decision that the RTD is open when resistance is much greater than expected range.  The AO-200 can detect an open loop on the .0035-.021 range because when this range is used, a current of 0 amps is far below the normal operating range and thus is open.  Also remember that the AO-200 is actively monitoring the output current via a sense resistor.  The feedback from the sense resistor is used to regulate the output current.  So when the module is trying to output .004 amps and sensing 0 amps, it can decide that the loop is open.  In the case of the 0 to 0.021 amp range, 0 amps is an expected state of operation, therefore it is not automatically a fault condition. 

In some cases you can evaluate the measurement from an input module and decide based on your application if the input is open. 

In the case of an output driving a 0 - .021 amp current loop, you could wire your loop such that it is monitored by an analog input.

[ltok]

Thanks for your reply.

But what about DI and DO modules?? Is there any way to detect the status of the device connected to it??

Thank you & Regards

Lee

[Wayne.C]

Lee,

I can think of one way to monitor a DI.  Kind of goofy but if someone really needed redundancy, it would work.  Wire AI and DI to same signal.  If a weak pullup resistor  to +VCC and pulldown resistor to COM were placed on DI input, the input would be 1/2VCC when input was open/floating.  Input signal could still drive the DI high and low.  AI could monitor voltage level on DI to detect open condition.

Not sure how to do a DO