Decent (good enough) digital scale

Discussion in 'Darkroom Equipment' started by michael_r, May 31, 2013.

  1. michael_r

    michael_r Subscriber

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    I only do occasional scratch mixing to experiment with things, so I can't justify spending serious $.

    This is for film developers in pretty small quantities. So I don't think I need a capacity of more than 200g. In fact 100g is probably fine. Resolution should be 0.01g.

    Is there anything accurate enough for $200 or less? There are some Ohaus scales around that price. I also found a company called MyWeigh. They make a small digital scale with 200g capacity and 0.01g resolution for under $100. But is it junk?

    Obviously for mixing photo chemicals I don't need some kind of crazy super precision thing. In fact if it were not for Phenidone resolution to 0.1g would be enough. But I don't want a piece of crap that's going to be materially wrong either.

    Thanks
     
  2. Hexavalent

    Hexavalent Subscriber

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    I purchased a small scale from Myweigh (can't remember the model offhand): 100 g capacity, .01 g resolution, less than $100. Quite satisfactory for my current emulsion-making needs.

    I would buy from them again, but a unit that can handle at least >200g to accommodate the added mass of a glass beaker etc.,

    The specs for scales can be misleading: resolution and accuracy are two different beasts. A scale with .01 gram 'resolution' may not be 'accurate' to 0.01 grams.
     
  3. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Michael, I'm on my 3rd balance, and I use a Kern School Balance EMB 200-2. It does up to 200g and its resolution is 0.01g, which is what you have asked for. I bought it for about €100. It is pretty good, realistically letting me have a precision of 0.1 with ease, and 0.04g with care. This one, like many in the under $400 range is of the design type known as "strain gauge". They either suffer from some "drift", which means that the reading slowly changes (in my case reading goes up about 0.01g every 10-20s), or they do not allow you to add small amounts, letting only larger added load to cause a displayed value to change. Of course, that second behaviour would be worse than the first for our needs, so I live with the slow drift, trying to be quick. The analytical design that uses electromagnets is more precise but much more expensive.

    I got mine from http://www.labunlimited.com/Online-...ing/School-Balance/Instrument/6-EMB200-2.html
     
  4. ntenny

    ntenny Member

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    I have some sort of ProScale, I think an LC50---one of the digital pocket scales that sell for a few tens of dollars, similar to the MyWeigh products (indeed I wouldn't be surprised if it the different brands all come from the same factory). It claims 0.01 g resolution, but for anything that fine I use a stock solution. In particular, I have a jar of phenidone in glycol and use that instead of relying on weighing out those tiny amounts of phenidone.

    For developer-in-small-batch uses, it's been absolutely fine for me. At the price point I don't believe it can possibly be as accurate as it claims, but I haven't seen that its limitations are a practical issue.

    -NT
     
  5. ath

    ath Member

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    True, but one rarely (or never) needs to weigh 100g with an accuracy of 0.01g.
    Imagine a wodden folding yardstick, 2m long. The accuray is nowhere near 1mm over the whole length but you can use it without problem to measure if a plate is 3 or 4mm thick.

    Additionally most electronic balances (or, more precisely, all balances which measure the force of gravity of a mass) need to be calibrated at the place where they are used. Force of gravity changes quite a bit depending on your location. The good old beam balance avoids this by comparing the force of gravity of two masses.
     
    Last edited by a moderator: Jun 1, 2013
  6. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    Check out meritline.com
     
  7. mgb74

    mgb74 Subscriber

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  8. Mark_S

    Mark_S Member

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    Back many years ago, I picked up a triple beam balance for next to nothing at a police auction. I don't know if they are still available that way.....
     
  9. mgb74

    mgb74 Subscriber

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    If you go this route, keep your receipt or clean the balance very well.

    Because you know what it's been used for. :smile:
     
  10. grahamp

    grahamp Subscriber

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    Sensitivity (responsiveness to small changes in weight) can be slow with these pocket scales. I find repeatability is reasonable to say 0.1g. Digital balances are at best only good to half the last digit anyway. Mine is good enough, and at under $20 dollars delivered, I am not complaining.
     
  11. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Michael, did you end up with a new scale that you are happy with?
     
  12. RalphLambrecht

    RalphLambrecht Subscriber

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    I'm very happy with all my digital scales; impressed actually, becauseeven though they have quite different limits,they all read the samewithin 1gfor a 10g calibrated weight; did not expect that. the only mistake I made:the 100g scale is very limiting ehen mixing normal quantities;200g would have been a better limit.
     
  13. Ronald Moravec

    Ronald Moravec Member

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    You need the heavy for sodium sulfite etc. Accuracy is not that critical so long as it is repeatable.

    A cheap digi is fine for 2 grams of metal etc, so long as it is repeatable. You will adjust your times to the resulting chemistry and be ok so long as you are within 10% .
     
  14. hoffy

    hoffy Member

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    Hey! Whats with this digital talk.... Wouldn't this be more appropriate on dpug.... :tongue:
     
  15. fotch

    fotch Member

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    One should only use an analog scale for analog photography. :laugh:
    So what do the dpugers need a scale for? :confused:
     
  16. craigclu

    craigclu Subscriber

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    I took a chance on a Tree 2500g scale that was very reasonable. It calibrates easily and I've checked it regularly against known weights on a $2000 rig at work and it is in agreement (and that scale is checked against a frighteningly expensive vacuum chamber scale). They're sold by an eBay seller....

    http://tinyurl.com/lhrn5of

    It has more than enough capacity for what I do. I use an RCBS reloading scale and convert to grains when playing with things in extremely small quantities, feeling that it is likely more accurate for that duty.

    FWIW: Our metrologist has told me that the lower priced scales tend to be most off of perfect at the extremes of their load cells. He recommended having 100g or more of weight before zeroing and then measuring your material when the cell is away from its normal zeroing point.

    Another hint with digital scales: Use negative weighing habits... Place a container of the material on the scale, tare and measure the negative weight displayed as you remove from the supply. This saves multiple attempts at just the right addition to the receiving vessel and prevents over pouring from things that cannot be reversed.
     
  17. nsurit

    nsurit Subscriber

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    I bought an inexpensive digital drug dealers scale from ebay which was a pain in the a%$ to use. I then bought a new triple beam which is a pleasure to use. Sort of like the old school cameras I ues. Bill Barber
     
  18. Edwin22

    Edwin22 Member

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    You must try on ebay or amazon because you can easily get portable digital scale with accuracy and other features that you want at less than $100 dollar. I have bought one at amazon in $35 with accuracy up to 0.1 gram.
     
  19. Xmas

    Xmas Member

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    mine was cheaper 0.01 gm resolution max 200 gm a new battery is going to be not much cheaper - came with 200 tare.

    it needs a selection of plastic bottle tops for chemicals like phenodine for which I need 0.07 gm for 1 l stock.

    simplest to drop the top in mixing container solution to get all the power out
     
  20. Edwin22

    Edwin22 Member

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    I am using PS-2001 counting scale. I have bought that few months ago and it provide me accurate results with other features that i need. It have accuracy limit up to 0.1 g with many features.
     
  21. dorff

    dorff Member

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    Hi Michael,

    I would get two scales. One for things like sulphite etc where the quantities are large and the accuracy not very important, and one for things like metol or phenidone where the quantities are very small and accuracy reasonably important. For the former you can use a kitchen digital or analogue scale. For the latter, get a reloading scale. My own strategy for phenidone is to dissolve a larger quantity in alcohol and to pipette the solution. Measuring 0.2 grams at a time is impractical, but Y grams dissolved in Y x 10 ml of alcohol is a 10% solution. It is easier to just weigh a single scoop and dissolve it in the appropriate volume, especially since it is so light and dispersible, and tends to fly in all directions when you transfer it. So if my scoop is 1.42 grams, I dissolve it in 14.2 ml and there we go.

    Fortunately we have very accurate balances at work, down to 0.0001 g, if there is anything I would need to measure to that sort of precision. But I can't think of any photographic application where that would matter.
     
    Last edited by a moderator: Jun 11, 2014