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  1. #1
    Join Date
    Aug 2010
    Posts
    1,739

    Charging scale reads steadily with swishing refrigerant?

    I find that CPS CC220 is affected a lot from refrigerant swishing around in the cylinder and dances around a whole ounce or two. (reads to 1/4 oz), but it reads steady with something like a dumbbell weight.

    Is CPS supposed to be decent?

    My 56 lbs shipping scale that reads to 1/10 oz reads much more steadily. It reads rock steady and the swishing liquid doesn't affect the reading.

  2. #2
    Join Date
    May 2011
    Location
    Oklahoma
    Posts
    361
    We have a cps in the cage at work. I used that once when I didn't have my inficon. I watched it go from zero to negative as I weighed it in then it stopped and headed back the other way. It was a bottle of virgin 134a in a factory bottle with one way valve and the unit was off. Indoors on a stable platform. No way it was moving or going backwards. coworkers laughed and I can't get it to do it again. piece o crap.

  3. #3
    Join Date
    Jul 2007
    Location
    Chicagoland
    Posts
    474
    Quote Originally Posted by ICanHas View Post
    Is CPS supposed to be decent?
    CPS is low end stuff for the most part, but if the load is in motion its going to effect any sensitive scale.

    I have a tif and it tells me if the wind is blowing too hard, but it will also weigh in a 5oz. domestic refr. charge.

  4. #4
    Most scales have a filtering that can be adjusted to compensate for noisy environments or vibrations. ALL scales bought should be calibrated with a certified weight prior to use. You can not just order a scale, open the box and use it, it MUST be calibrated, which can also help drifting issues as well.

  5. #5
    Join Date
    May 2011
    Location
    Oklahoma
    Posts
    361
    I've never adjusted mine...

  6. #6
    Join Date
    Aug 2010
    Posts
    1,739
    Quote Originally Posted by jamuz View Post
    Most scales have a filtering that can be adjusted to compensate for noisy environments or vibrations. ALL scales bought should be calibrated with a certified weight prior to use. You can not just order a scale, open the box and use it, it MUST be calibrated, which can also help drifting issues as well.
    I don't subject them to unreasonable level of noise for the intended application. Refrigerant swishing around in the jug on scale placed on concrete surface is mostly side-to-side motion and shouldn't affect the reading much.

    I'm just not really impressed that the CPS 220 doesn't perform as well as my 56 lbs x 0.1oz Digiweigh shipping scale and it was costlier than the shipping scale.

    As for calibration. I don't think it makes much of a difference. One point calibration is to compensate for gravitational difference.

    If you bring a scale calibrated in Mexico City to Copenhagen, DK, it's going to read 0.37% high but that's about as extreme as it gets. While 1000.0 oz will read 1000.37oz, it's not an offset that will read 0.37oz off across the entire range. It's a proportional difference. So, zero it out at 1000oz and a difference of 100oz represent a change of 100.037oz, which is close enough to 100oz in this field.

    If a 10oz box weighs 10oz on empty scale but weighs 11oz on top of 45 lbs box after the scale's been zero'd the linearity is off and that usually means the load cell is bent from dropping something on the scale.

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