Sensors中的主题 Re: TPMS waterproof

TPMS waterproof

tiago_silva — Tue, 03 Feb 2026 21:48:56 GMT

Hi,

We intend to use the FXTH871xD, Tire Pressure Monitor
Sensor, in our project. But we work with tires filled with water, to increase the traction of a tractor. My question is, after a properly resin process, can the pressure port be in direct touch with water under pressure?

Thanks, Tiago MS#

Re: TPMS waterproof

TomasVaverka — Thu, 14 Mar 2019 09:37:46 GMT

Hi Tiago,

Thanks for your interest in NXP's TMPS!

I need to discuss it with the product group and should have an answer tomorrow or beginning of next week.

Best regards,

Tomas

Re: TPMS waterproof

TomasVaverka — Fri, 15 Mar 2019 06:54:06 GMT

Hi Tiago,

Here is the answer from our product group:

No, the gel is not 100% hermetic, and therefore over some time, a few weeks at 1500kPa, water molecules can be forced under pressure into the gel and eventually reside near the wirebonds of the Pcell, or near the top surface of the MCU. In these cases, the dielectric constant of the water allows capacitance changes of the sensitive transducer interface circuits. This new capacitance results in offset and/or sensitivity shifts to the calibration. Since there is no reference for the SW to compare, the application will not recognize the shift as artificial, and instead treat as a real pressure change. It is possible the shift can be out of tolerances.

The module should be designed in such a way that it maintains separation from the sensor to the water, and the separation methods must allow access to the pressure.

Best regards,

Tomas

Re: TPMS waterproof

tiago_silva — Fri, 15 Mar 2019 12:38:34 GMT

Thanks, Tomas.

I appreciate your help. I will think in how to protect the pressure gate from the water without block the pressure...

Best regards,

Tiago