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General => Technical support => Topic started by: psayesr on November 16, 2002, 04:28:54 PM

Title: rtd
Post by: psayesr on November 16, 2002, 04:28:54 PM

I need read 2 rtd (pt100) sensor with T100MD888+PLC, please give me any sugestion.

Thank alot

Title: Re: rtd (PT100 sensor)
Post by: support on November 17, 2002, 07:23:07 AM

The quickest means is to buy a commercial PT100 signal conditioner that will output 0-5V, 0-20mA or 0-20mA (the latter two can be converted into voltage by using a 250 ohm resistor) and connect to the T100MD888+'s analog input.

You can also build a two-resistor voltage divider using the PT100 as one of the resistors and construct a simple opAmp to amplify the voltage drop across the PT100 resistance into 0-5V.  A sample circuit can be found at the following link:

http://www.tri-plc.com/applications/PT100Interface.pdf

Title: Re: rtd
Post by: rosssyscon on September 10, 2003, 04:04:42 AM

We just hooked up an RTD using the diagram from page 6 of the installation guide. Rather than a 1K Ohm Pot, we have a 100 Ohm RTD. (Using T100MD-1616+)

So far it works just fine. This allows us to bypass the expensive converter. Are there any problems with this? Are we going to experience problems later?

Title: Re: rtd
Post by: support on September 10, 2003, 11:00:09 AM

I assume you are using the RTD in series with a resistor to provide the voltage dividing effect as outlined in the document:

http://www.tri-plc.com/applications/PT100Interface.pdf

The only thing you need to check may be whether self-heating of the RTD may affect the readings slightly, but there should not be any long term ill effect on the connection.