BX-08AD-1 Analog Cards

[jrayb]

I have several of the cards installed & operating correctly. I have a warning. I open I/O System View & select the module that has the warning & it has Missing External 24VDC. I have verified that I do in fact have 0 volts & 24VDC at the required terminals. I have a two of these modules on the Master PLC, 4 on one slave & 4 on another slave. They are all triggering this warning. Any help would be appreciated.

[Greg]

I assume when you say "slave," you are using BX-DMIO. Are you using the 24VDC supplied by the BRX PLC's (or DMIO's) power terminal? Or an external 24V supply? If an external one, is there a difference between the grounds (0VDC) of the 24VDC supply of the BRX PLC (or DMIO) and the one supplied to the analog module? Because, obviously, the BX-08AD-1s "think" they don't have 24VDC supplied and are reporting this back to the various CPUs. As a test, if you are using an external 24VDC, can you disconnect that and try using the BRX PLC's (or DMIO's) 24VDC supply?

[jrayb]

I am using a BX-DM1E-M-D. I am using an external power supply as the DMIO nor the BX-DM1E-M-D don't offer 24VDC power output. In one cabinet I have a BX-DM1E-M-D & the analog cards +24vdc wired to one common point & the 0VDC of each unit wired to a common 0VDC point. How can I use the 24VDC of a unit, if that unit doesn't supply 24VDC?

[Greg]

How can I use the 24VDC of a unit, if that unit doesn't supply 24VDC?

Well the fact that you are using the BX-DM1E-M-D and the BX-DMIO-M-D, of course, means you can't. I installed a BX-08AD-1 here and tested it. Of course, mine worked as expected. With no +24VDC then I got the warning. With +24VDC, no warning. Also, by default, the 08-AD-1 is 4-20mA and will report "broken transmitter" with no connection. But if I configured it for 0-20mA, then no "broken transmitter" error.

The analog cards have the supply terminals inverted than what is normally expected. 0V is on top, 24VDC is on bottom. Are you sure they are wired up properly? And you are measuring the 24VDC at the terminals of the analog modules themselves? Because, otherwise, I'm running out of ideas. It should just work.

[jrayb]

I will check the 24VDC wiring at the terminals.

[jrayb]

I finally had time to check the wiring. All wiring is correct. I have two BX-08AD-1 analog cards on the PLC which have no warnings. All of the BX-08AD-1 cards on my BX-DMIO-D units are reporting missing 24VDC. The BX-DMIO-D cards are on the same 24VDC power supply as the BX-08AD-1 analog cards are in their respective panels.

[Greg]

What happens if you try these two things?

• Power cycle just the analog modules after CPU power up? (e.g. unplug the +24VDC from the analog but not the CPU, then plug it back)
• Power down, unplug the CPU from power, power up (so that just the analog module is powered), then plug the CPU to power.