problem with dry air media in MPVZ

[mikesadi]

Dear madam/Mr
in order to measure specific level of the liquid in time, we need to an instrument like a pressure sensor or whatever can be installed in our tank and can operate in 0 to 4 Kpa (in 1000 range) for control of the level
actually we plan to have around 12 to 15 mm constant height of bioethanol (in 72 centigrade) -
please consider 15mm height is equal 118 pa or 1.2mb .
Please consider we have tried some pressure Sensors like NXP products (MPVZ) which  But it operates only with dry air!
how  can we solve the problem? in which way can we use the sensor without becoming destroyed it

i hope ur company can recommend a solution 

[reyes]

Hi,

Although water level it is marked as a typical application for some of the MPX pressure sensors, I need to advise, that for all NXP standard pressure sensor products, any environment other than dry air, will may have some impact on the reliability and lifetime of the product. NXP's silicon pressure sensors are NOT compatible with oil, gas, petrol and can be affected by water or water vapors, or other chemicals.

As for the "Level of reliability, Lifetime, Mean Time Between Failure", our data is for dry air only (as specified in the datasheet).

A determination must be made if this impact is acceptable for the application.

Possible solutions to use our sensors in applications with other media than dry air:
Besides the mechanical stresses to the inside of the package, there would also be a need to evaluate stresses the hardening/ed material induce on the outside of the package. To minimize these, a low stress encapsulant should be used. And, of course, any recalibration/autozeroing of the device after a point of potential stress induction would be highly recommended and could alleviate any mechanical stress concerns if done before a measurement (and the temp delta's are minimal during the readings).
In the application note AN3728 is discussed the media compatibility for the NXP Pressure Sensors. In this application at page# 3, you can see that we have tested a couple of media and using the Air column method (Figure 2 of this document) to measure water level is unlikely to have issues, but we cannot give a guarantee about the long term reliability of these devices under these conditions.

AN3728: https://www.nxp.com/docs/en/application-note/AN3728.pdf

There is another Application note AN1950 that explains how to measure water level, the difference is that for this document the designers used a MPXM2010GS which output need to be amplified, for the case of the MPVZ5004, the output is already amplified so it can be inputted directly to the microcontroller’s ADC.

You can find the gerber files, schematic files and software files from the Water Level Reference design from the Application Note AN1950 in the following link: https://www.nxp.com/products/no-longer-manufactured/water-level-reference-design:RD1950MPXM2010GS?ta...

I hope this information is useful.

Thanks,

Jose

NXP Semiconductor