Hello,
I'm planning to prototype with the XTR105. I spent some time in the datasheet and the reference design guide, "Analog Linearized 3-Wire PT100 RTD to 2-Wire 4-20mA Current Loop Transmitter Reference Design".
I'm having a little trouble understanding how you calculate the output current of the transmitter. For instance, in section A.3 of the design guide, a calibration is performed where RG is trimmed to provide an output current of 19.987mA. How was 19.987mA calculated? I understand there are equations provided but they depend on Vin(Vin+ - Vin-), but Vin is not quite obvious since the device manipulates the excitation current through Rlin1 and Rlin2.
I've also looked at the calculator "xtr_calc_10-23.xlsx" but loop current calculation doesn't look anything like that in the design guide or datasheet.
Any clarification on this appreciated, thanks.
Zack