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I’m trying to test a HART hardware both in master side and slave side , I’m using A5191HRT HART modem IC from Onsemi, (because only its HART modem IC founded in shops our city), the biggest Disadvantages of this IC is circuit sample is low in internet, rather than other HART modem IC from TI , AD , MAXIM.

The main problem , I’m Involved in it, how HART voltage applied across sense resistance in master side can effect on current of current source(slave) and transmit HART data from master to slave side ?

In the real circuit I have tested , voltage across sense resistance cause current flow in itself circuit (get out from Op-Amp output pin and enter to GND master– red line ) (GND and VCC in master and slave is separate – two separate power supply)

While, what is expected to signal transmit from master to slave, I’m thinking that signal should pass from blue line.

In the experiment, I’m increasing the value of sense resistance to 10kohm and cause voltage applied sense resistance flow from red line

enter image description here How I can solve this problem and transmit HART data from master to slave ?

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  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Jul 20 at 7:48
  • \$\begingroup\$ The circuitry should be much the same regardless of whose chip you are using. Currently your circuit doesn't even work for 4-20mA. Simply put, HART superimposes FSK audio over the 4-20mA loop. Get your 4-20mA circuit working first. \$\endgroup\$
    – Kartman
    Jul 20 at 12:43
  • \$\begingroup\$ 4-20mA working very well , by changing V11 voltage source between 0.26v to 1.23v , current changing between 4 to 20mA. I checked in practice \$\endgroup\$
    – tech.elec
    Jul 20 at 15:15

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