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  1. #27
    Join Date
    May 2012
    Location
    Upper Michigan
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    3,588
    Il put another 50, we can drop my digi's and save the analogs by not dropping them.

  2. #28
    Join Date
    May 2008
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    SouthEast
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    249
    Quote Originally Posted by mason View Post
    We putting paychecks on this challenge : )?

    I've got 50 says my DC's are more accurate this second, forget dropping them 20' it's over already.
    I don't have anything against the digital gauges... Other than my frugal nature.

    Now, just present me with the parameters for how we're going to compare and measure said accuracy on said system...

  3. #29
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,401
    Put a drum of 22 in an ice chest, get her down to 32*, hook up and see what the pressure is. No messing with the calibration screw on the analogues once its hooked up.

  4. #30
    Join Date
    Feb 2007
    Location
    Fremont, Indiana
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    1,424
    Quote Originally Posted by jbeckham View Post
    Ha, this is hilarious...

    Lets parlay and add full retail market price for each others gauge set...

    I'm gonna be laughing about the gig all the way through, but unless you just turned over a fire engine red quarter... You, probably not so much...
    I can barely look at my analogs without the guages breaking!
    I'm sure it is partially due to the abuse my ak's take daily, I forget to baby the dinosaurs!

    sent from my Samsung Galaxy Note
    Member of the "Work Exchange Program"
    "Will work for knowledge"

    "Everyone is a genius. But if you judge a fish on its ability to climb a tree, it will live its whole life believing that it is stupid"
    A Einstein

  5. #31
    Join Date
    May 2008
    Location
    SouthEast
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    249
    Quote Originally Posted by jtrammel View Post
    Put a drum of 22 in an ice chest, get her down to 32*, hook up and see what the pressure is. No messing with the calibration screw on the analogues once its hooked up.
    Why would I adjust the screw afterward? The gauge will will read 0 psig in the same manner as 57.5 psig...

    if you didn't adjust at atmospheric pressure, you wouldn't be accounting for elevation...

  6. #32
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,895
    It appears the digi-queen nest has been stirred again LOL!

  7. #33
    Join Date
    May 2008
    Location
    SouthEast
    Posts
    249
    By the way, if we aren't working on cryogenic processes with these gauge manifolds...we're really taking this discussion to far...and if we are, we're probably not going to be using them...

    So again, I will state my case that they are just more than the trade requires...unless your doing cryogenic lab grade work...in which case you won't be using a manifold gage set you purchased over the counter at the local parts house...

  8. #34
    Join Date
    May 2008
    Location
    SouthEast
    Posts
    249
    I just wanted to get a point across to the OP that the trade doesn't require that much of an initial investment on a gauge manifold to be a successful tech.

  9. #35
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,895
    Quote Originally Posted by jbeckham View Post
    Why would I adjust the screw afterward? The gauge will will read 0 psig in the same manner as 57.5 psig...

    if you didn't adjust at atmospheric pressure, you wouldn't be accounting for elevation...
    On analogs you would be better off leaving a drum in your house at about 74*/130psi, confirming bottle temp with a calibrated temp sensor, and setting your needle to 130psi on high side, with a different bottle at 32*/57.5psi to set low side needle. You might be surprised where those needles land with 0psi after that calibration.

    Or buy some digi-cools : P.

    I've been using some analogs for the past couple weeks with my separate temp sensors and wow do I hate it now. The parallax thing is real, hook your analogs up to a bottle in your shop, then have one person at a time go in alone without sharing any information and ask ever tech to write down the psi and the face saturation temp on a piece of paper. You will not get the same numbers.

  10. #36
    Join Date
    May 2008
    Location
    SouthEast
    Posts
    249
    Quote Originally Posted by mason View Post
    On analogs you would be better off leaving a drum in your house at about 74*/130psi, confirming bottle temp with a calibrated temp sensor, and setting your needle to 130psi on high side, with a different bottle at 32*/57.5psi to set low side needle. You might be surprised where those needles land with 0psi after that calibration.

    Or buy some digi-cools : P.

    I've been using some analogs for the past couple weeks with my separate temp sensors and wow do I hate it now. The parallax thing is real, hook your analogs up to a bottle in your shop, then have one person at a time go in alone without sharing any information and ask ever tech to write down the psi and the face saturation temp on a piece of paper. You will not get the same numbers.
    i will argue that what you are calling parallax is just the difference in opinion on where that needle is on the dial... unless you have a gauge graduated in 1 psi increments, there will most likely be some discrepancy in interpretation every time...

    and as far as where the needle comes back to, if it's not within 1% of the test sample for our respective gauge ranges... i guess it's time to swap it out...

    for what it's worth, managing and understanding error is just part of understanding physics... there is a time and place where it matters, and there is a time and place where it really, really matters... looking at that hodgepodge split system that was originally installed 8 years ago by some other jack-leg that never even looked at the duct work... is not one of those times.

    its all relative, and what your are doing with your gear will dictate your kit...

  11. #37
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,914
    Quote Originally Posted by jbeckham View Post
    I can get on board with the inherent 0.5% accuracy, and the 0.75% scale accuracy... but, parallax error from the lens...c'mon man... the face of the gauge is maybe 8mm below the lens...and it just a 1x protective lens. Just take off the lens if it bothers you that much...
    The reading still changes with the angle it is viewed at, or which eye you are squinting at it with.
    Then there is the PT chart interpolation error.

    With digitals, you don't even have to look at pressure, you get a direct saturated temperature reading, which is what you really need.

    At what point do you rule out that a digital instrument won't be incorrect either, just because it's a solid state device doesn't mean it can't be wrong.

    At least with analog gauges I can carry around 3 or 4 sets and compare measurements between them if I suspect something is wrong
    There is a 9 year span in instrument ages in this picture. They are from 3 different manufacturers, use 4 different types of pressure transducers, and 4 different types of 3 different technologies of temperature sensors.
    There is only about a 1.5 psi difference between the lowest and highest pressure reading, and 1.1 difference in the temperature probe readings among the 4 instruments that have temperature probes. The BTD-1000(top left) has no temperature probes.
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    Furthermore, lets drop an analog manifold and a digital manifold from the top of a 20' extension ladder and see which one is more accurate afterwards... I'm gonna contend that both sets of gauges will be junk...
    I'd put some money on the table that says my Digi-Cool DRSA-1250 would still work fine. The manifold it is mounted on may need to be replaced though.
    My BTD-1000 has survived such a drop, onto concrete.
    If more government is the answer, then it's a really stupid question.

  12. #38
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,110
    I completely disagree with Jbeckham; however, I strongly suggest against buying digital gauges until you have been in the business for 2 to 3 years.

    1.) some people get into the trade and find it is not what they are looking for so an expensive initial investment goes down the drain.

    2.) You need to spend time getting not just accumulated with analog gauges but proficient with using superheat sub-cooling. I don't mean learn the math, I mean you understand what it truly is, how it helps you, and the physics of what you can't see.
    Although digital gauges do not prevent you from learning this stuff, knowing how to use the rudimentary tools precisely comes with a very strong understanding that will make you a confident self-aware technician.

    3.) New guys break stuff left and right. Its a growing pain trust me it will happen.

    4.) You will most likely spend your first 6 months to a year in someone elses van. Do you really want to let other people use your crazy expensive tools day in and day out? Do you really want to move those tools from van to van and lug them out every night.

    5.) By the time you are really ready to use these tools and have your own van something better will have replaced them on the market.

    6.) Make sure any digital gauges you purchase have a respectable micron gauge. A bad micron gauge setup will turn your would upside down on large equipment like chillers.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  13. #39
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,914
    Quote Originally Posted by jbeckham View Post
    Why would I adjust the screw afterward? The gauge will will read 0 psig in the same manner as 57.5 psig...

    if you didn't adjust at atmospheric pressure, you wouldn't be accounting for elevation...
    And what does altitude have to do with what is going on inside a hermetically sealed system?

    Altitude does not change the PT relationships inside a sealed system, the saturated pressure at a given temperature will be the same at sea level as it would be at 20,000 feet.

    Gauges need to be calibrated in the pressure range they are intended to operate in.
    Zeroing the gauge actually introduces more inaccuracy into the gauge, especially at higher elevations where the atmospheric pressure is lower.
    If more government is the answer, then it's a really stupid question.

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