Sensor Problems

chenbingjy

Sensor Problems [Copy link]

 

I designed a pressure sensor circuit, as follows: Now there is a problem, the voltage value at the AD port is sometimes there and sometimes not, I input a force value, and the output is 0V. Can an expert take a look and see where the problem is? Thank you!

maychang

The voltage value at the AD port is sometimes there and sometimes not. When a certain value is input, the output is 0V. Check whether the potential of the two input terminals is within the common mode range allowed by INA188.

chenbingjy

Thank you! I am a newbie and I don't understand your reply at all

littleshrimp

Check whether the theoretical output of the sensor meets the requirements after amplification. Check whether the polarity of the sensor output and the developed connection are correct. Check whether the sensor and the amplifier share the same ground (the instrument amplifier does not accept floating input).

chenbingjy

Correct polarity, common ground.

littleshrimp

chenbingjy posted on 2019-1-13 10:39 The polarity is correct and the ground is common.

Check these three parts separately. First check whether the sensor output voltage is normal, then check whether the amplifier circuit works normally, and then check whether the adc sampling is normal.

chenbingjy

Now the amplifier circuit is not normal, the output is always 0V

btty038

Let's connect step by step to see where the problem is.

littleshrimp

chenbingjy posted on 2019-1-13 13:09 Now the amplifier circuit is not normal, the output is always 0V

In- grounded in+ connected to power also output 0V?

chenbingjy

It is not connected that way. This board has been made for several versions, and it has been adjusted continuously. It sometimes does not work, but it is fixed after some tinkering. When I used it, I added a weight, and it felt that the value jumped a bit. When I tried the last version, the polarity was reversed at the beginning, and the sampled value was negative after adding a weight. When the polarity was reversed, there was no output.

littleshrimp

chenbingjy posted on 2019-1-13 15:23 It's not connected that way. I've made several versions of this board and have been constantly adjusting it. Sometimes it doesn't work, but I just tinkered with it. When I use it, I add a weight and it feels...

According to your second question, the sensor's operating voltage is 8~15V. What is the sensor power supply voltage when you actually use it? What method do you use to provide it?

littleshrimp

chenbingjy published on 2019-1-13 13:09 Now the amplifier circuit is not normal, the output is always 0V

The output of the amplifier is related to the output of the sensor. You can use a multimeter to measure the output of the sensor to see what it is.

chunyang

The circuit must be complete. If the input is intermittent, check the welding first.

chenbingjy

littleshrimp posted on 2019-1-13 19:40 According to your second question, the sensor operating voltage is 8-15V. What is the actual sensor power supply voltage when you use it? How do you provide it?

There may be a problem here. I use 5V, which may be wrong.

chenbingjy

littleshrimp posted on 2019-1-13 19:43 The output of the amplifier is related to the output of the sensor. Use a multimeter to measure the output of the sensor to see what it is

It cannot be measured, it is too small 0~10mV