My AD628 differential circuit has been troubled for several days because of the wrong voltage.

yyftju

My AD628 differential circuit has been troubled for several days because of the wrong voltage. [Copy link]

I use AD628 to sample voltage signals differentially, and both T2 and T3 are AD628. The IN+ sampled by the T2 circuit is about 13V to 22V, and IN- is 2V. By adjusting RX1, the voltage signal output is basically Uo=IN+IN-, which is very accurate. However, the AD628 of T3 is equivalent to a subtractor. IN+ is a voltage signal of about 13 to 20V, and IN- obtains a 10V reference voltage through a voltage divider circuit. This is achieved by adjusting the gain of the AD628 to 1 by adjusting RX2, which is equivalent to a subtractor. However, when IN+ is less than 16V, the output signal is always about 6.8 and basically does not change. However, when IN+ is above 17V, the out signal obtained begins to be normal, which is the difference between IN+ and IN-. What is the reason for this? It has been bothering me for a long time. It should be fine after reading the DATASHEET manual.

电子微创意

Dual power supply is fine.

yyftju

Electronic Micro Creativity published on 2016-3-31 23:24 Dual power supply is fine.

Can you give a little more details about the improvement of the AD628 circuit of T3 and where the problem lies?