MPXM2102D pneumatic connection

[romans]

Hello

I have some trouble with the pneumatic connection to the sensor MPXM2102D.

The idea was to use an O-ring seal between pressure sensor and pneumatic block. During test I see that I have too much leakage. A closer look shows that the metal plate is slightly movable (red arrows in pic) Air can escape between metal plate and plastic housing. For test purpose I seal to the plastic housing. Then no air was escaping. The datasheet and the application note "Mounting Techniques, Lead Forming, and Testing of the MPX Series Pressure Sensors" says nothing about mounting.

I have the following questions:

Which sealing is recommended?

Which force to sealing is allowed?

Thanks for helping

greeting Roman

[reyes]

Hi Roman,

The cap is not attached with glue or silicon. The plastic package holds the cap, so it is natural big leakage occurs when only the center hole is sealed.

It is not recommended to seal/glue the metal plate and the plastic housing for final applications, but for engineering evaluation, any idea would be possible as long as the package is sealed and center hole is opened. I think silicon such as RTV would a candidate for this evaluation. The silicon should not touch the surface of gel.

I would recommend the customer to use the MPXM2102GS for final application instead of the MPXM2102D to avoid any additional process to attach a port.

MPXM2102GS works in the same manner than the MPXM2102D and have a very similar package (MPAK package) but it have already a port on the top.

MPXM2102GS datasheet: www.nxp.com/assets/documents/data/en/data-sheets/MPX2102.pdf

Have a great day,
Jose

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[romans]

Hello Jose

Thanks for your answer.

You write it is not recommended to seal/glue the metal plate and the plastic housing for final applications. What is recommended? Use a flat sealing to connect the sensor to some other component (in our case a pneumatic block)? Is there a specific limitation of force to sealing at which the sensor doesn't work correct anymore?

We don't want use the MPXM2102GS sensor because the pneumatic block with valves shall connect directly to the sensors without any tubes

Greeting Roman

[reyes]

Oh ok, I see, then I think that for this case it should be possible to glue the metal plate and the plastic housing as long as the package is sealed and center hole is opened.

Silicon such as RTV would be the best solution for this evaluation, but also make sure that the silicon do not touch the surface of internal gel.

Have a great day,
Jose

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[romans]

Hi Jose,

We don’t want use RTV silicone because it is not a very safe process for medical device and not appropriate for high number of devices. We suggest a solution like in the picture with a flat sealing.  Is this solution appropriate or does it harm the pressure sensor in any kind? Is there a specific limitation of force to the top surface of sensor?

Have a great day,

Roman

[reyes]

Hi Roman,

You can use any type of glue/silicone, this should not cause any problem on the sensor performance or sensor body material, however, make sure that the glue does not goes inside of the sensors otherwise there could be error on the measurements or internal damage of the sensor material.

The solution you are proposing in the image would be definitely preferred, this way you avoid apply force to the metallic part of the sensor and prevent leakage from the gap between plastic housing and metal plate as in the previous version using the O-ring.

As per the force limitation to the top part of the device, I’m pretty sure that there is a limit, but it is not characterized. But since the force would be applied to the external plastic case instead of the metallic plate, it should be able to support more force.   

Have a great day,
Jose

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[romans · Accepted solution]

Hi Jose,

Okay then we will do it with a silicone sealing. Thanks for helping.

Have a great das,

Roman