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Thread: Pressure/vacuum gauges etc

  1. #1
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    Pressure/vacuum gauges etc

    Not a smart project but another that I need pressure data for, both above and below atmospheric - so gauges required. Can anyone tell me if this is a vacuum gauge?

    101775-1.jpg
    Link to page here >> https://www.newfrog.com/product/dry-...yABEgLzifD_BwE

    And, what do I need to place between a gauge (pressure and/or vacuum) and pressure chamber which will fluctuate between above and below atmospheric pressure to obtain a pressure or vacuum reading, ie some form of fast operating check valve that can operate at 50 to 150Hz? There is no requirement to 'trap' the reading as in compression testers. The range of pressures for the above is +/- 1.4bar and for another measurement (pressure only) circa 1.1 bar but with momentary 4bar peak.
    Any ideas anyone (TK!)?

  2. #2
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    That will only display negative pressure, it's gonna hit the end stop if you try and go above atmospheric!
    (But it IS a vacuum gauge)

    You need one that has leeway eitherside of atmospheric , AKA a compound gauge Like this one
    https://www.ebay.co.uk/itm/Compound-...%3D&rmvSB=true

    just for instance ^^

    You need to pick one that has the range either side that you require obvs.
    You're so money supermarket and you don't even know it!

  3. #3
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    Buy an electronic pressure sensor and use an Arduino or ESP12 to send the data to your phone or PC.

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    Quote Originally Posted by Mjolinor View Post
    Buy an electronic pressure sensor and use an Arduino or ESP12 to send the data to your phone or PC.
    Two problems there.
    One, the pressure only measurement is hot - exhaust gas released from the cylinder hot.
    Two, no electrical power available as working outside due to CO poisoning concerns - for now at least. Maybe in the longer term but still the heat issue.
    Three (actually), my complete ignorance and incompetence when it comes to things computerised - for now at least....

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    Quote Originally Posted by reinaldo_is_spam View Post
    That will only display negative pressure, it's gonna hit the end stop if you try and go above atmospheric!
    (But it IS a vacuum gauge)

    You need one that has leeway eitherside of atmospheric , AKA a compound gauge Like this one
    https://www.ebay.co.uk/itm/Compound-...%3D&rmvSB=true

    just for instance ^^

    You need to pick one that has the range either side that you require obvs.
    Cheer's RIS. That's what I had in mind before I found dedicated pressure OR vacuum gauges.
    So, say two of those gauges connected to my chamber in which the pressure alternates between above and below atmospheric pressure. What in the way of check valves (reversed flow direction for one relative to the other) do I use to have one gauge read vacuum only and the other pressure only?

  6. #6
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    Quote Originally Posted by pinger View Post
    Cheer's RIS. That's what I had in mind before I found dedicated pressure OR vacuum gauges.
    So, say two of those gauges connected to my chamber in which the pressure alternates between above and below atmospheric pressure. What in the way of check valves (reversed flow direction for one relative to the other) do I use to have one gauge read vacuum only and the other pressure only?
    I think the problem you'll encounter is if you insert one way check valves to avoid +ve on the vacuum gauge and -ve pressure on the pressure gauge is they also will hold the reading: i.e. you will need some bleed off somehow.

    Say you have a pressure of 1bar applied on the pressure gauge (with a oneway check valve fitted) , then release that pressure in the pipework the gauge will still be showing that pressure reading ... because of the check valve .... same thing with the vac gauge.

    I think you'll have to put up with a single compound gauge ? or find some way of slowly bleeding off any current reading once that vac/pressure is removed.
    You're so money supermarket and you don't even know it!

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    Quote Originally Posted by reinaldo_is_spam View Post
    I think the problem you'll encounter is if you insert one way check valves to avoid +ve on the vacuum gauge and -ve pressure on the pressure gauge is they also will hold the reading: i.e. you will need some bleed off somehow.
    .
    Well spotted RIS!
    Thinking about this, I don't think I need the check valves after all.
    When there is vacuum the subsequent positive pressure (compression) will be low, and when the vacuum is negligible the subsequent positive pressure will be high. That should be enough especially if I can deduce the peaks from what will be an average reading that I can then compare to the (hot) pressure (which doesn't need check valve). Absolute values would be good though - but without check valves....

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    Quote Originally Posted by pinger View Post
    Well spotted RIS!
    Thinking about this, I don't think I need the check valves after all.
    When there is vacuum the subsequent positive pressure (compression) will be low, and when the vacuum is negligible the subsequent positive pressure will be high. That should be enough especially if I can deduce the peaks from what will be an average reading that I can then compare to the (hot) pressure (which doesn't need check valve). Absolute values would be good though - but without check valves....
    From the potential values you need to monitor that gauge I linked to would be ideal ...
    You're so money supermarket and you don't even know it!

  9. #9
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    Quote Originally Posted by reinaldo_is_spam View Post
    From the potential values you need to monitor that gauge I linked to would be ideal ...
    Realising that I will be reading either pressure or vacuum, I've ordered two pressure gauges (as the pressure is of more interest in the fluctuating chamber than vacuum) and a vacuum gauge to read the vacuum in said chamber before compression commences. All in 0-1bar range which better suits the application than the (4bar) combination gauge and all from the site you linked RIS so cheers for that.

    Thanks also Mjoliner re the suggestion of going computerised but for the reasons given, and the need to see an immediate reading on dials as I alter test parameters on the fly, mechanical gauges it is - for now. Maybe later I'll pick your brains re Arduino (or Raspberry Pi?) in relation to setting up control of actuators if needed. The gauges are to tell me what actuators I may need to manipulate the pressure differentials so a first step in this project.

    Thanks for the help guys, much appreciated.

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