Measuring of pressure in a center board (Sailboat)

[fredma-1]

Hello,

I am working in a school project right now that involves putting sensors on a sailboat. In this case a Dinghy pico.

One of the tasks is to measure the pressure on sides of the centerboard (A retractable keel in the middle of the boat), to see which sides is more pressured. So I only want to look at the difference between one side and the other.  

I thought that a differential pressure sensor could be good, so I looked at some differential pressure sensors like MP3V5010 and MPXV7025. 

But from what I can understand from the datasheets is that.

1. They are only built for dry air, so that is going to be a problem. The tube/pipe that is meant to measure the pressure is going to be exposed to water (in the water), so there is a high probability that water is going to get to the sensor if the boat tips over (which is common). 

2. Those sensors (MP3V5010 and MPXV7025) can only measure P1>P2. The sensor MPXV7025 has a range of -25 kPA to 25 kPa, but it still says in the datasheet that P1 must be higher than P2.  How can I measure -25 kPa if P1 must be higher than P2?

So my questions is can I "waterproof" the sensors? (put something in the pipe or such) Or is there some sensors that are better suited for this kind of applications, that are not sensitive to water? 

[reyes · Accepted solution]

Hello,

Other media than dry clean air has the potential to dissolve, or be absorbed by the gel and corrupt the die surface or lead to wire-bond breakage. Some types of media will take longer to corrupt the die than others, so a disposable application is possible.

I would like refer you to the application note AN3728: “Media Compatibility for IPS PRT Pressure Sensors” that would be worth to be considered in addition to the provided information.
In this application note at page# 3, you can see that we have tested a couple of media, mainly on parts having media resistant gel, but we cannot give a guarantee about the long term reliability of these devices under these conditions.

One possible solutions to use our sensors in applications with other media than dry air is to try to use a “Media Resistant Gel” type pressure sensor.

NXP uses two different types of gels in order to isolate the die from the environment:

1. The Fluorosilicone Gel (Type FE-53) is being used for all our standard type of pressure sensors.
2. Media Resistant Gel (Sifel) is being used for our pressure sensors that are used e.g. in high temperature environments, mainly in automotive applications

Since I’m assuming that you would need a pressure sensor capable of measure both a positive and negative pressure within the same system, I suggest you to use one of the MPVZ7025DP pressure sensor.

This is also an Integrated Pressure Sensors, which means that are already Factory Calibrated, Temperature compensated and Signal conditioned, so the external hardware needed its minimal (Capacitors for decoupling and filtering only).

Unfortunately the MPVZ7025DP is no longer manufactured by NXP, but you can find this device in Rochester Electronics, which is an authorized distributor for NXP obsolete devices.

I hope one of these mentioned sensors can be helpful.

Have a great day,
Jose

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[fredma-1]

Thank you