The sensor amplifier circuit has no output

chenbingjy

The sensor amplifier circuit has no output [Copy link]

 

The above is my sensor circuit diagram. The magnification is switched through a CD4051. The sensor is 10 tons, model YZC-219. The output sensitivity is 2.0+-0.04mV/V. I choose to magnify 1000 times in the program, INH1_1 is low level, A1, B1, C1 are high level. When a person steps on the sensor hard, the voltage of C90 is 0 and remains unchanged. I don't know if the resistor is correctly connected between XI_1 and XO_1 of INA188, but it is difficult to measure the resistance when powered on. I don't know what to do? Please give me some advice, thank you!

topwon

Give it a thumbs up

maychang

What kind of sensor is yours? The sensor is not shown in the picture, so it is hard to tell. Judging from the "10 tons" and "stomping on the sensor", it is probably a strain resistor. It is not possible to directly connect the two ends of the strain resistor to the two input ends of INA188. A power supply must be applied to the strain bridge. In addition, how much force can be applied by "stomping on it"? At most 5000 Newtons. And the time is so short that C90 has no time to respond.

hankaifeng145

The REF reference is connected incorrectly. Please look at the PDF document again.

xiaxingxing

hankaifeng145 posted on 2019-5-21 18:27 The REF reference is connected incorrectly, please look at the PDF document again

When REF is not needed, REF can be directly grounded. “Reference input, This pin must be driven by low impedance or connected to ground.”

chenbingjy

maychang published on 2019-5-21 18:15 What kind of sensor is yours? The sensor is not shown in the picture, so it is hard to tell. Judging from the "10 tons" and "stomping on the sensor", it is probably a strain resistor. ...

It is not a strain resistor. When CD4051 was not connected, it was OK to connect 150 resistors at both ends of RG. It just cannot adjust the magnification. Now that CD4051 has been added, it does not work.

hankaifeng145

I didn't check it carefully just now. You can connect it to ground because you are using positive and negative 5v power supply.

hankaifeng145

You can write the 4051 program when the magnification is 1 times, and use a multimeter to measure the output of INA188, which should be around 0V, and then increase the magnification. When no external force is applied, the output should be around 0V, or it may be negative.

maychang

chenbingjy posted on 2019-5-21 18:42 It is not a strain gauge resistor. When CD4051 was not connected, it was OK to connect 150 resistors at both ends of RG. It's just that the amplification factor cannot be adjusted. Now that CD4051 has been added, ...

What is the internal resistance of 4051? It is much larger than your 49.9 ohms and 100 ohms. Besides, your signal is both positive and negative. The op amp uses dual power supplies, and CD4051 should also use dual power supplies.

xiaxingxing

When the 4051 is powered by 5V/GND and at 25°C, the typical on-resistance is 270 ohm and the maximum is 1050 ohm.

chenbingjy

Thank you! I will ask the person who designed the circuit

chenbingjy

That person is at a loss. Can anyone tell me if there is any good solution? Thank you!

chenbingjy

Can I change the chip?

lct2000

Change the design, the internal resistance is large