Dear sir/madam,
I designed a temperature detection circuit with INA826. The components on the circuit are selected by RTD_Linearization_v7.xls downloaded from TI.com. When I connected Pt100 to the circuit about 150ohm at 140 degree, the voltage output from the circuit is only 2.67*(3.3/(10+3.3))V rather than 6.7*(3.3/(10+3.3))V. The circuit is enclosed.
I am looking forward to your reply as soon as possible.
Regards,
Qian.Miao
Miao Qian,
The schematic shown in the RTD linearization spreadsheet assumes that the INA826 is powered from dual supplies, which allows its input common mode range to be very close to 0V without limiting the output voltage. For single supply operation, an input common mode near 0V with the REF pin grounded will limit the output voltage swing as indicated by Figure 12 in the datasheet:
I simulated your circuit in Tina and got similar results to what you describe. Here is the output voltage with dual supplies (+/- 12V):
and here is the output voltage with only a single 12V supply:
It looks like you can use an op amp to provide a low impedance voltage source for the RTD bridge. This would bias the input common mode up to a range that would allow for single supply operation of the INA826:
