I am having too many sensors failing, its MPXM2202GS, about 30% within 2 months after installation.
They are used to measure water level with air column between water and the sensor, the sensors were installed upside down.
1) Using 5vdc as power supply
2)Using pulsing, so the sensor is only On for 10% of the operating time as recommended in the document AN3728
3)I used/tried to insert silicone oil by putting the sensors in vacuum to remove the air and replace it with silicone oil
4)Sensors were installed up-side-down as recommended in the document AN3728
5)There is an air column between sensors and water, so basically we followed the advice in "AN3728, Media Compatibility for IPS PRT Pressure Sensors"
6)Temperature is between 10 and 30 Celsius and all devices installed inside, so no harsh environment
7)The applied pressure is within the range of the sensor (0 to 200Kpa)
8)I noted that the silicone oil (very thick) got out of the sensor port when installing the sensor up side down. It took three or two days before all the silicone oil comes out
When I tested the failed sensors the resistance between Out+ and Out- where infinity while its about 2K2 ohms on a good/new sensor.
So what have we done wrong here?
Is it possible that putting the sensor in vacuum has affected the gel layer of the sensor?
Was it better if we did not try to put silicone oil at all?
any idea how to improve life of the sensor or solve the problem of the failing sensors?