M580 output to intelligent positioner SRD998

[AlexandrePPrado]

Dear All, 

We are going to participate in an exhibition in the field of sugar and alcohol and one of the main technical schools will exhibit a skid with our products.
The chosen PLC was M580. For skid flow control, the SRD998 was selected.
As both are Schneider products the presentation of this working set will have a big impact on customers.
We currently have a problem with the 4 to 20 mA output signal: The maximum output impedance of the M580 (BMXAMO0802) is up to 300 ohms and the impedance of a smart positioner (SRD998) is approximately 450 ohms.
Does anyone have any suggestions on how to make them compatible? Maybe with external power?

 Thank you,

Alexandre Prado

[MatthewM]

We have experienced possibly the same issue when upgrading Quantum I/O to X80, where on some field devices the X80 AO just can't drive enough mA in the loop to get proper actuation.  In these cases the sparkies have been putting in loop isolators like these:

https://www.intech.co.nz/product/xid-l/

https://www.intech.co.nz/product/xid-p1/

which has resolved the issue we encountered.

[AlexandrePPrado]

Thanks Matthew,

Unfortunately I believe that using this isolator (or similar) is the only alternative.

[alidav]

Like you, I have a problem with this positioner, which turns on with the output of the PLC, but cannot be commanded correctly. I tested it with the fluke calibrator and it doesn't turn on  but it turns on with the druck calibrator. 

the load impedance of positioner is 420 ohm and the analog output of siemens has a max impedance of 500 ohm Which apparently shouldn't be a problem because they are within the allowed range.

[AlexandrePPrado]

Hello Alidav,

The positioners are intelligent but require a little more energy from the electronic card (DCS or PLC). This impedance matching issue is occurring more frequently. In your case, theoretically, it should work. Perhaps the impedance of the cable or a small deviation in the card's power supply is limiting operation.
In my case, it was necessary to add a repeater with greater load capacity as another M580 card was not available at the time (BMEAHO0412 or BMEAHO0410).

Thank you for commenting on this issue.

[alidav]

hello alexandre

I used an isolator and the problem was solved

Thnks for your reply