Needing some help with a SquareD to SLC500 Series Conversion...

[jmobley]

I am working on a conversion from a SquareD PLC to a SLC series PLC. I have run across one issue that I can not seem to overcome. The older system currently uses "Analog Devices AC2626" temperature probes to monitor the system. The signals ran to a RIM-125 Analog Input Module on the SquareD PLC. When looking at the DIP switch settings (SW1) on this module I first noticed that none of the standard ranges were set (such as 0-5V, 0-10V, 0-20mA, 4-20mA, etc.). When attaching these signals to an analog input card (1746-NI8) on the SLC PLC, I can not get the signals to work properly. I believe this to be because of the way the probes were set up on the old system.

On the orignal system there is 24VDC tied to one leg of the AC2626 and the other leg is tied to the analog input card (RIM-125). Because the card is not set up with a standard range as described in the SquareD manual, it almost seems like that card is just running wide open.

Is there a known way to interface an AC2626 probe to an SLC analog card and make it function as it does/did on the older system?

 

[jdbrandt]

I am working on a conversion from a SquareD PLC to a SLC series PLC. I have run across one issue that I can not seem to overcome. The older system currently uses "Analog Devices AC2626" temperature probes to monitor the system. The signals ran to a RIM-125 Analog Input Module on the SquareD PLC. When looking at the DIP switch settings (SW1) on this module I first noticed that none of the standard ranges were set (such as 0-5V, 0-10V, 0-20mA, 4-20mA, etc.). When attaching these signals to an analog input card (1746-NI8) on the SLC PLC, I can not get the signals to work properly. I believe this to be because of the way the probes were set up on the old system.

On the orignal system there is 24VDC tied to one leg of the AC2626 and the other leg is tied to the analog input card (RIM-125). Because the card is not set up with a standard range as described in the SquareD manual, it almost seems like that card is just running wide open.

Is there a known way to interface an AC2626 probe to an SLC analog card and make it function as it does/did on the older system?

That probe's data sheet says that its a current-source device, 2-wire, with micro-amp/degree C rating, so, you're right...it is not standard. the minimum output is 0.2 milliamps...

You'll need to rig up an op-amp and juice up the signal so that your plc can read it, I'm afraid.

OR, use 0-20mA, and see what kind of signal you can get out of it...depending on your precision needs.

 

[Mickey]

The data sheet I see is that probe you have is just a thermocouple. Type J,K or L. I would determine what type you have and buy a standard thermocouple transmitter (see link) to provide a standard 4-20ma output for your analog input card.

http://www.analog.com/media/en/technical-documentation/data-sheets/AC2626.pdf

http://www.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Temperature_Sensors_-a-_Transmitters/Temperature_Transmitters_%28Thermocouple_Input%29