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I am trying to build a pressure sensor ( PSI gauge ) that will be used to measure and monitor the pressure in a pool water filter. These generally have a mechanical pressure gauge like this....

enter image description here

What I want to do is use this Freescale Pressure Sensor so that I can electronically monitor the water pressure in the filter. However, it is not waterproof and would mostly certainly be destroyed in little time if used to measure the pressure of a liquid.

Anybody have any idea or experience with use such a sensor in a manner that provides accurate readings while protecting the sensor from the water?

Any other methods that work well for this sort of thing?

Cost is a factor here. I can't spend a lot of money.

Edit: might something like this water pressure sender for cars work?

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  • \$\begingroup\$ Grease slug in sensor pipe. | Sealed-top vertical tube with open bottom inserted in tank and near tank bottom. As fluid level rises air in tube is compressed. Sensor at top of tube or fed via a capillary. (Washing machines often uses a similar arrangement with a mechanical pressure switch). | Sealed flexible container or with sealed box with diaphragm. Benign liquid in sealed container matches external pressure. \$\endgroup\$
    – Russell McMahon
    Dec 18 '13 at 11:24
  • \$\begingroup\$ @RussellMcMahon I'm having a hard timer visualizing that arrangement. I don't have the option of putting a sensor at the bottom of the tank. All I can do is put a sensor or something in a gauge that is screwed into the top of the tank. Would the pressure of the water be transmitted through a layer of protective layer of silicone placed in a tube connected to the pressure port? \$\endgroup\$
    – Chimera
    Dec 18 '13 at 16:59
  • \$\begingroup\$ This question falls more in the realm of mechanical than electronic design, but for a start, consider an air-filled bladder submerged within the filter. Pneumatically plumb it to the sensor outside the filter. Protect the sensor from rain, dew, and splashes. Sealing the filter around the pneumatic plumbing is, as they say, left to the reader as an exercise. \$\endgroup\$
    – JRobert
    Dec 18 '13 at 21:20
  • \$\begingroup\$ Read my above description slowly and draw it - should be clearer. Or, peruse this drawing :-) : constructionmanuals.tpub.com/14279/img/14279_183_2.jpg . Tube is shown here external and tapped off bottom BUT a closed top tube with open end inserted into tank does the same job. When empty bottom of tube is open to ambient and p=atmospheric. Arrange so as soon as filling starts bottom is closed and from then on p_tube = head pressure. Gauge can be fed via a capilliary to get mechanical separation amnd a grease or similar slug in gauge tube can block direct moisture path. \$\endgroup\$
    – Russell McMahon
    Dec 19 '13 at 7:40
  • \$\begingroup\$ ADDED: As pressure will be above atmospheric the above arrangement may force water to above tank surface level depending on air volumes. If lower tube dia is larger diameter than upper section then the large lower volume when forced into upper part will create a larger pressure than if tube was of constant dia. eg if P = 3 atmosphere then you need to reduce volume to 1/3. \$\endgroup\$
    – Russell McMahon
    Dec 19 '13 at 7:47
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Omega is a good source. There are probably cheaper solutions. But in my experience Omega Stainless Steel Transducers are bullet proof. http://www.omega.com/pptst/PX309-100mv.html

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  • \$\begingroup\$ Thanks for the information. However, too expensive for this project. Happy Holidays! \$\endgroup\$
    – Chimera
    Dec 17 '13 at 20:42
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I was in the same need as you for a remote water pressure gauge (non mechanical. I have a micro hydro system and need to monitor the pressure in my penstock before the turbine which is outside and I could have run a 25' small line and fitted a gauge on it but at times it's not heated during winter and would freeze. After much searching I bought an oil pressure garage with the remote electronic sensor. The first one I bought stopped working in a few weeks I figure the spring etc in the sensor couldn't operate in corrosive water. I bought a second one tht the sensor looked ore made of brass and that one has been working now for 4 years. The gauge and the sensor is a cheap offshore and I know is not as precise but it gives me good enough data for my needs. Its possible with that sensor you placed a link to in your posting and with an electronic oil pressure gauge it would work better. The weak link is the sensor, an oil pressure gauge can say "oil pressure" on it but who cares! As long as it gives psi! Good luck Patrick

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  • \$\begingroup\$ Thanks Patrick. Do you happen to have a part number of reference to the oil pressure gauge you are using? \$\endgroup\$
    – Chimera
    Dec 18 '13 at 18:50
  • \$\begingroup\$ I don't have a part number , its an offshore no name oil pressure gauge I'm using. I've been meaning to try out better ones. The fellow who recommends the stainless steel transducer is probably right on. As far as the actual pressure gauge, if the have a gauge, good quality, from the same place you get the transducer. I bought my cheap one at an supply store here in Canada called Princess Auto. I'm doing this on the economy end also. Again, I've just been trying the oil pressure gauge and sending unit (transducer) because I've yet to find a water one. Patrick \$\endgroup\$ Dec 23 '13 at 16:44
  • \$\begingroup\$ Thanks again Patrick. Have you heard of MisterHouse automation system? \$\endgroup\$
    – Chimera
    Dec 24 '13 at 11:54

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