Trying to measure gauge pressure in a water pipe (under 1 psi)

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Discussion Overview

The discussion revolves around measuring and regulating gauge pressure in a water pipe, specifically targeting a pressure of approximately 0.75 psi (1.8 ft H2O). Participants explore various methods and products suitable for this low-pressure application, including digital manometers, analog transducers, and alternative measurement techniques.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in finding an inexpensive pressure transducer that accurately measures under 1 psi for water and suggests using an analog transducer that outputs voltage.
  • Another participant proposes a digital manometer as a potential solution, providing a link to a specific product.
  • A later reply questions the suitability of the suggested digital manometer for fluids, indicating uncertainty about its compatibility.
  • Another suggestion involves using a U-tube manometer filled with a denser liquid, such as highly salinated water, to improve measurement accuracy.
  • One participant mentions that blood pressure cuffs have gauges indicating mm of mercury and suggests using a sense line filled with water to avoid air bubbles, along with adjusting the gauge reading based on its position relative to the pipe.
  • Participants discuss the cost of industrial sensors, noting that while some are available for around thirty-five dollars, many are prohibitively expensive.

Areas of Agreement / Disagreement

Participants present multiple competing views on the best approach to measure gauge pressure in the specified range, with no consensus reached on a single solution.

Contextual Notes

Some suggestions depend on specific conditions, such as the type of liquid used in manometers and the need for adjustments based on the gauge's position. There are also unresolved questions regarding the accuracy and compatibility of suggested digital manometers with fluids.

Mike415
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I'm trying to measure and regulate gauge pressure in a pipe that has water flowing through it, but I need the pressure to be about .75psi (1.8 ft H2O).
Most dial gauge ranges are too high and not accurate enough.
Pressure transducers I've had no luck with as far as finding one that's inexpensive and measures accurately under 1 psi for water.
Using a liquid column would be too high for water (2 ft).
So any ideas, products or guidance?

I have no problems using an analog transducer that outputs voltage if that's a good option.
 
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How about a U tube manometer filled with a denser liquid (possibly highly salinated water with food colouring to show the interface.)
 
Blood pressure cuffs have a little gage that indicates mm of mercury.

1psi is about 51.7 mm hg

You'll want the sense line filled with water and sloping up all the way to pipe so air bubbles aren't trapped.

And you'll adjust reading of gage for its distance below pipe centerline.

The electronic sensor in a home monitor might be something you could scrounge. Those instruments show up in thrift shops.

That's a not uncommon range for industrial sensors but they cost hundreds of dollars.

A component like this is around thirty-five bucks at Digikey.
http://www3.panasonic.biz/ac/e_download/control/sensor/pressure/catalog/bltn_eng_psa.pdf?via=ok

http://www.digikey.com/product-search/en?mpart=ADP5121&vendor=255
 

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