Pressure Sensor Calibration

We have all equipment ready, so we go to calibrate the pressure sensor. The U-tube manometer and the electronic pressure sensor were connected together and the air pressure source was added to.

The U-tube reference manometer setup

In the first concept, the small 6V electric compressor from a personal blood pressure meter would be used as a pressure source. But, there was strong problem with the air leakage when the compressor stops. This was not solved by using any of electromagnetic valves after the compressor.

The piston actuator as a reference pressure source

Finally, the piston actuator from old medical machine was used as a very reliable pressure source and it gave exactly the range we need for sensor calibration. There was no leakage in this setup, so if we set the pressure value by the piston move, it will remain without any further change.

A little strange, but reliable connection to U-tube

Water columns balanced in the U-tube

Water columns unbalanced in the U-tube

Finally, we take several values of the pressure represented as a water column heigh difference in the pipes and as the counts value from the electronic sensor. Data from the U-tube manometer were converted into kPa and arranged in the table along with data from the sensor. Then the data was fitted by line and its constants were obtained.

Then, constants were implemented into microcontroller in the main unit. We can measure the air pressure in Pa directly now. Constants was implemented in long integer multiplied by 1000.