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Allen Bradley Isolator model 931-TD002 query

Allen Bradley Isolator model 931-TD002 query

Allen Bradley Isolator model 931-TD002 query

Hello Support,

I'm on site trying to commission application with several Allan Bradley isolators model 931-TD002. This is a new system not being tested before.
Isolators were installed to isolate/split 4-20mA signal into two outputs.
As per dwg. we are simulating signal directly to isolator terminals 41&42 and for a very short period of time mA signal is present on isolator output and than it goes to "open loop". In order to get it work again need to recycle the power for isolator.
All isolators are same model and have identical behavior.
Could not find detailed manual for this particular isolator. Any suggestions, similar experience.

Thanks a lot

RE: Allen Bradley Isolator model 931-TD002 query

931-TD002 is the publication number.

If you have the basic 931N-C122 splitter, input is on terminals 3 &4, outputs on 1&2 and 5&6. It needs 24VDC power.

If you have the A222, then you get to play with the DIP switches

And if you have the X422, it's designed for bipolar inputs and presumably 4mA in is an elevated output on -20 to +20mA input range.

RE: Allen Bradley Isolator model 931-TD002 query

Thanks Danw2 for prompt reply. In fact the model is 931S-U561 and it doesn't have dip switches. See attached photo showing more details.

RE: Allen Bradley Isolator model 931-TD002 query

1. Splitter or not, that is the question.

The 931-U561 is listed as a splitter in the 931 product brochure, but A-B does not use the term 'splitter' like I do.


I use the term splitter for one 4-20mA input, two 4-20mA outputs.

But the minimalist description and the product description for 931 universal input modules describes the U561 as having a single 4-20mA output and a discrete digital output. So, yeah, two outputs, but only one is a 4-20mA.



The product migration bulletin (from the old series to the new series) does not refer to the -U561 as a splitter, but as a single output device.


2. Wiring

The -U561 wiring diagram shows
- the 4-20mA input on terminals 11 (+) and 12 (-).
- The single 4-20mA output is on terminals 41 and 42.
- The 4-20mA output is loop powered, so one of those terminals must be +24Vdc from the loop power supply.
- The other output is the digital output on terminals 51/52


If you're expecting a 2nd 4-20mA output on terminals 51/52, I think the -U561 is the wrong module.

3. Configuration necessary for a simple isolating repeater?

Configuration for a simple splitter is not necessary, but the -U561 is not a simple splitter.
The product description in one doc (screen shot 03 above) states, "Configure analog and digital output options" and "Configuration via on-board buttons/enocder or FDT/DDTM program".

Another doc with the wiring diagram says the current input is "Configurable".

I'm guessing you probably need the software configuration package (Pactware, a Windows app, the 931 DTM device descriptor file, and the USB/serial converter cable, p-n 931A-CB) in order to tell the box which input it's looking for, what the digital function is, and what the 4-20mA should do in a fault condition. Maybe the 4-20mA action is telling you, "I'm not configured".



The module might not know which input it's looking for and setting the failsafe fault mode to 'open circuit', which is why the 4-20mA momomentarily appears then disappears.

I tried loading the DTM in Pactware, but when Pactware could not detect the USB/serial cable, it stalled and wouldn't open the device, so there's no way to tell what's next in Pactware.

The instruction sheet for downloading the DTM and installing it in Pactware is attached.

RE: Allen Bradley Isolator model 931-TD002 query

Thanks Danw2 for taking time on this.
In the meantime we have also received a confirmation from our vendor saying this isolator/splitter is not correct type for our application i.e wrong parts were installed inside control cabinet.

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