Differential Pressure Sensor

Hello Guys!

I would like a suggestion on what could be the best way to connect a 26PCAFA6D (differential pressure sensor) with Arduino and extract data from it and use them for measuring flow speed. based from the datasheet of this sensor I see that it uses Wheatstone bridge principle.

So currently I’m thinking to connect a differential amplifier to bridge output in order to increase voltage level for Arduino. And then sent it to analog input of micro-controller in order to process it further. At this point I would like your opinion guys. Is this the right way of connecting this sensor and using it properly with Arduino.

Attached you will find Datasheet and a block diagram that I plan to use

26PC_series.pdf (499 KB)

1.PNG

Yes, that is how it is done. A sensor with the raw wheatstone bridge outputs is typically connected to an instrumenation amplifier like the INA125 and then to the Arduino.

An instrumentation amplifier has high impedance inputs, and its gain is set with a seperate resistor with seperate pins of the amplifier. With a normal OpAmp, a feedback resistor sets the gain, but because of the that resistor, the input is no longer high impedance.

There are other options:

  • For a quick test, connect both outputs of the sensor to the Arduino. It will be very inaccurate, but you should be able to check if it is working with enough pressure output.
  • You could buy a sensor with analog output 0-5V, then you don’t need the amplifier.
  • Using your sensor, but with a digital instrumentation amplifier.
  • A digital sensor that does everything (sensor + amplifier + ADC) inside the chip more accurate.
  • Some microcontrollers have a amplifier inside. The Arduino Uno doesn’t have that, but the Leonardo and Mega do.

Thanks a lot! I tried to connect it directly to Arduino without any amplifying stage as you suggested and it has some resolution and range.

Now I'm trying to use it with an Analog-to-Digital Converter (MPC3421) to have a better resolution because I want to measure pressure differences in terms of Pa (Pascal) which I think it's not easy with this type of sensor. My pressure values should be on the range from 1 Pa to 2000 Pa

If any suggestion for some type of sensor that has this range and it has all blocks (sensor+amplifier+ADC) integrated would be great!.

The MPC3421 does not have the voltage reference available to feed the wheatstone bridge. I don't know if that has influence. With a wheatstone bridge, the actual voltage is not important.

If you scroll down on this page, you see that the INA125 also poweres the bridge : Wi-Fi Body Scale with Arduino - Open Electronics - Open Electronics

The digital amplifiers for a bridge sensor is for example the AD7799. There is a schematic in the datasheet, it shows that the positive and negative power voltage of the bridge are taken into account with refin- and refin+.
The LTC2411 also takes into account the power voltage of the bridge.
There must be many more of those chips.

At freescale, the sensitive sensors are not digital. I don't know why.

Up to 2kPa with 1Pa resolution. That is very sensitive. I don't know if digital pressure sensors exist for that. I think that an analog pressure and digital chip is the best option. That way you can exchange the sensor, and try 16 or 24 bits chips.

There is another option to get about 4Pa accuracy (maybe). The BMP180 is a baromic pressure sensor. It is very sensitive an factory calibrated. You have to get two sensors completely inside your air system. Just calculate the difference between two sensors.