HART Multiplexer Issue


Thread Starter


Dear Members,

I need some advice regarding HART Mux problem. I tried to retrieve HART data from our 4-wire pH transmitter using P+F KFD2-HMM-16. But I also need to split the signal into two outputs, going back to PLC and DCS. I use MTL5544D to split the signal. I put the splitter after HART mux. The problem is, after I installed the splitter, I could not retrieve the HART data. 4-20 mA signal was perfectly split into two signals. I still got HART data before I added the splitter. Below is the order of our circuit :

4-wire transmitter --> P+F KFD2-HMM-16 through Hart Termination Block P+F FI-PFH-NS0137 --> MTL554D splitter (terminal 1 and 3) --> PLC and DCS

Does different grounding on transmitter, hart mux, and splitter affect the HART signal?

Appreciate your opinion or any idea on this issue.

Dear Ikhtiander,

Thank you for your reply. I know that 5544d can not support hart for 4 wire transmitter. That's why I put it after hart mux. My idea was to strip the hart data first by hart mux, then let the 4-20 ma signal split by mtl5544d. But it did not work either. I lost the hart data after i added mtl5544d into circuit (but not before). Is that possible because I added mtl5544d into circuit, somehow the hart data get "grounded" or something?

Does anyone now what circuit inside splitter that does not allow hart to pass?