I want to thank everyone which could give me more information about the possibility to manage a wachdog digital output on the ION device , this point is requested by the customer for bidding to a project of power monitoring
The aim of this request is to notify the DMS for the good avaibility of devices .
A possible software solution is to use a Data Monitor Module inside VIP that monitors some measurement from the ION meter.
However if you use the "Worst Case Limit" under certain limit, you might get a false alarm which can be confused with the device response time.
Eg. let's say ... a meter in a long RS485 loop might require 5 sec. to respond in VIP (1sec min pooling). If you set the "Worst Case Limit" (setup register of the Data Monitor Module) to 5 sec you will get a false alarm (that the meter is not communicating).
I would say that 10 sec. for the "Worst Case Limit" would do it.
I don't have a standard approach to this, as we don't have a dedicated watchdog output. But we have great flexibility with regards to configuration of the meter. I think part of it is determining what is meant by "good availability" of the device. One possibility is to configure the meter so that the logic controlling a digital output is tied to a quantity that should always be present, and therefore the output would always be ON. The customer would then need to have a wired connection to the meter's output, to monitor its status. If that output's signal was lost, that would indicate a problem with the meter. If the intent is to simply monitor for possible communications loss, that should be done through the associated software.
I think there is an output register that is connected to the internal firmware watchdog on the device. If it is still present in the latest firmware then it is likely on either the Display Options module or may be the Factory module. On the original 7500 meter this was linked to the alarm LED on the front panel. Since this is just a normal output register it would be a simple framework change to link this to a digital output module to send pulses to the outside world.
Note that just because an output is ON does not mean that the device is still sane. It is quite possible that the device could lock up and still have an output asserted (at least while the device is still powered up). Determining availability is actually a complex problem to solve once all the possible failure modes start to be analyzed (both internal and external to the device).
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