I have the following sensor:26PCAFG6G

The output of the signal is a differential output from a Wheatstone bridge with 0 - 1 psi, or 0 - 70.3 cmH20 corresponding to 0 - 16.7 mV, I am using AD623AN for the instrumentation amplifier. I apply gain around 49.91, with the resistor of 2k to apply the gain, to fit the measurement scaling to the ADC.

Here is my circuit: Instrumentation Amplifier Circuit

I intend to apply the sensor with this configuration. On one end I will apply pressure with a bag, and the other will be the discharge place of the water. Here is my setup:

Sensor Setup Use

However, I haven't got any significant pressure measurement, as when the water flows through, it only provides around 1.2 mV, when I used a multimeter to read the two points of the Wheatstone bridge. I have calibrated my pressure source, and it is measured to around 44 cmH20, which should be sufficient, and the voltage should be more than 1.2 mV. Here is my oscilloscope reading when I applied the gain by 50.

Oscilloscope Measurement

Would like to know if the sensor is used correctly and if someone has an experience with this particular sensor.

The question is, how is it to interface this sensor, and what went wrong?

Thank you.

  • \$\begingroup\$ I believe this is for the calibration of the sensor with 44cmH20. I think it's a great idea, and I will try to do this. I will have a vertical reservoir with a certain area above ground and connect the bottom of the reservoir with the 44cm water height. I often try to exert pressure by closing the outlet end and pushing a water/air pressure with a syringe, this results in a measurement (which I haven't calibrated yet) but at least it shows changes in the voltage. I wonder if this sensor is meant for flow-through or just when we close the outlet, it will provide a measure of pressure? \$\endgroup\$ Aug 5, 2022 at 10:04
  • \$\begingroup\$ The flow rate won't affect the pressure measurement. \$\endgroup\$
    – Andy aka
    Aug 5, 2022 at 10:13
  • \$\begingroup\$ why would you expect significant pressure reading? ... the output port of the pressure sensor is open to atmosphere \$\endgroup\$
    – jsotola
    Aug 5, 2022 at 22:53
  • \$\begingroup\$ That's something I would like to know if the sensor measures the atmospheric pressure, it would have a significant reading of the atmospheric pressure. But the datasheet doesn't say anything about accounting or discounting the atmospheric pressure. \$\endgroup\$ Aug 9, 2022 at 7:49

1 Answer 1


Would like to know if the sensor is used correctly and if someone has an experience with this particular sensor. The question is, how is it to interface this sensor, and what went wrong?

Why don't you block the outlet end and make a vertical inlet that can contain up to 44 cm of water? In other words, do what it says on the tin and don't overcomplicate the situation with flowing water.

You could also keep the water topped up to the correct level in the upper reservoir and use a pump to draw out the water but return it to the upper reservoir so that, in effect, the pressure remained constant and no water was lost.

  • \$\begingroup\$ Thank you for your reply, but I think this is my emphasis of the task, which is to use this sensor to measure pressure with flowing water. I have contacted the company that made the sensor, and it claimed to measure the pressure while the water is flowing, but not enough instructions on how to calibrate or use them in certain settings. I will provide the diagram that the company provide in the main text. And sorry, do you refer to "tin" as the datasheet? Hopefully, I am wrong about the flow-through nature, and it is not meant for water-flowing. \$\endgroup\$ Aug 5, 2022 at 10:37
  • \$\begingroup\$ "do what it says on the tin" (in Britain) means use it as instructed and without over-complication. The flow rate won't affect the pressure measurement @Lactobacillus \$\endgroup\$
    – Andy aka
    Aug 5, 2022 at 10:42
  • \$\begingroup\$ I understand, thank you. I need the pressure while the water is flowing to see the fluctuations of pressure when the reservoir is emptying the system because there will be mechanical effects applied to the water reservoir from the inlet. I want to observe time-variant data on the pressure. \$\endgroup\$ Aug 5, 2022 at 10:52
  • \$\begingroup\$ Thank you, I will try to utilise a water pump. \$\endgroup\$ Aug 5, 2022 at 10:58
  • \$\begingroup\$ @Lactobacillus please take the 2 minute tour to understand why folk give help for free. \$\endgroup\$
    – Andy aka
    Aug 13, 2022 at 12:57

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