Hello
What are some of the typical reasons for receiving PV_BAD signals?
Cheers for your help!
pv current > "(20mA+3%)" or < "(4mA-3%)"
If using a HART PV then a BAD status from a transmitter may cause PV_BAD, even if the 4-20mA is in range.
In reply to andrewduffy:
The BAD status on the CHANNEL propogates up to the AI Block in the module and the block erro mask can be configured to set BAD ACtive on the block, and this is used for BAD_PV alarm.
If the signal is within range, then this is no NAMUR status option on channel.
If channel is not bad due to IO card internal issue (i.e. bad a/d converter, or other), and HART is enabled on the channel, then the HART Errors should be checked. If these are "not ignored", check which is set and address at the source. You can also ignore the HART based errors so the signal reverts basically to a non-HART 4-20 mA behavior.
The variable status in HART may be set due a transmitter issue. But if there are problems with HART communications, you can ignore the HART information on the 4-20 signal to avoid spurious PV_Bad alarms, but keep the device alerts working for maintenance purposes.
Andre Dicaire