Problems with current sampling and op amp circuits

Thread Starter

sheng Ke

Joined Jun 23, 2019
11
ACS725.jpg

The theoretical current is 10sinwt A, first use ACS725LLCTR-30AB-T to convert the current into a voltage amount, and then the amplifier.
The following questions exist:
1. The ACS725LLCTR-30AB-T has an initial voltage of Vcc / 2, and the 1A current is converted to 0.033V voltage. A slight fluctuation will make the error larger. I don't know if there is a better circuit to replace it.
2. When only testing the op amp, it was found that the voltages on pins 2, 3, 5, and 6 were not equal, and the chip was not damaged. I don't know what happened.
Please give pointers, thank you
 

Thread Starter

sheng Ke

Joined Jun 23, 2019
11
Is R7 really zero ohms?
What type is the op-amp?
Yes, in fact, the input of the op amp is 1.65 + 0.033 * 10sinwt. It can be found that the front and back multiples are too large. The purpose of this design is to reduce the previous 1.65, and try to be within an order of magnitude with the sine coefficient. The input subtractor, I don't know if my expression can be clear, but now I use LM358 for this op amp. No matter what the input is, pin 2 is always about 1.8V (at this time, the reverse end is 3.3V).
 

AlbertHall

Joined Jun 4, 2014
8,834
With R7 as zero ohms and the positive bias on pin 2, the output on pin 1 will be very close to zero. Therefore pin 7 will also be close to zero.
 
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