I have noticed that the 2/4AI RTD ST (6ES7134-4JB51-0AB0) module varies a measured temperature of my pt100 climatic with steps of 0.03 degrees Celsius where my sm1231 varies a measured temperature with steps of 0.01 degrees with a similar pt100 climatic sensor as I would have expected from the et200s module as well.

In theory, both should respond the same, as both do 15bits + sign. Both have separate 4 wire pt100 sensors connected. The temperatures do not need to match, but the steps between measurements should be in 0.01 degrees Celsius and not 0.03.

This is what I am talking about:

Tips anyone?

mopS04

hi norbert,

do you look at the input_word direcly?

regards,

 Hi,

yes, I look at %IW80, that shows me 1843 for instance. I change that integer to real and divide that by 100. That would result in 18.43. I have tried all smoothing options, but pt100 sensors on the et200s RTD module keep showing steps of 0.03 instead of 0.01

These are 2 pt100 sensors of different brands on the et200s RTD module, as you can see, they both vary the measured temperature with 0.03 degrees Celsius:

To be absolutely sure, I traced the %IW of both sensors in parallel to the "calculated" value and the result is exactly the same. The %IW value shows resolution steps of 3 instead of 1:

After having exchanged e-mails with Siemens Technical Support, I was told that they know of no other customer with similar issues and if I would like to escalate to development, no fix would be issued, no matter if they could reproduce the error or not. This, because the product is being phased out.

We have 50 sensors with ALL OF THEM showing this out of spec behavior. For me a clear indication that firmware is the issue and just to be sure, I purchased a 2 AI RTD HF module, also for the ET200s. A 6ES7 134-4NB51-0AB0 module to be exact. I removed one of the modules that was producing out of spec results and replaced it with the HF module. Same wiring, same base-unit, same programming, same everything and guess what...the problem is gone. Clearly a firmware issue as I had expected all along. I have researched this so much that I think that I know what the issue is in the firmware. A very silly mistake that only surfaces when using high resolution.

Unfortunately, it won't be fixed, because this module is being phased out and that trumps a product performing out of specs apparently.