FX-120i calibration weight; Does grade/class really matter?

[Tsu45]

I was about to order an F1 class calibration weight on ebay after watching a youtube video on scale calibration. Started thinking about it, does that really matter for our purposes since we all do load workup and look for signs of pressure along the way? It's really just a relative measurement as long as my scale is calibrated to the same physical weight every time, shouldn't matter if my calibration weight is 49.987g (my RCBS chargemaster weight) or 50.000g.

I could see the importance if loading to an exact known max charge right off the bat with no load development, but that's not how any of this works.

 

[ngb1787]

I do calibration on my fx 120, in 5 years it has never been off,

 

[Ned Ludd]

You spent a fair bit of coin buying a decent balance. Why not purchase a good quality calibration weight set to go with it? Calibrating a balance with a weight whose actual/true weight is slightly off from the expected value may not affect the precision of the balance at all. It would affect the accuracy. However, as long as the calibration weight value was pretty close, you may well never notice anything. Nonetheless, why purchase a good balance and then cheap out on the calibration weight? That approach doesn't make a lot of sense to me.

 

[Dud]

With the slightly older version Auto-trickler that I borrow, I make standards for each charge weight using small centrifuge tubes filled with lead weights and spilled powder.

That way when I throw charges, I'm essentially calibrating at the target weight.

I keep my standards in a centrifuge tube box so I don't have to worry about dust or other things throwing off the weight but I do check to make sure the scale agrees with my standard before I start throwing.

With the new app that sets the charge weight, calibration is more important but if you are off by 0.04 grains, it's probably not a big deal and you should be consistently off by that amount if it's due to a calibration standard that is off.

 

[Ccrider]

Exactly how do you calibrate an fx120i?

 

[JimSC]

I am not a instrumentation guy but for me it is the precision the scale has not it's accuracy that matters. As long as the scale gives the same reading for the same amount each time you are OK. That being said I calibrate with a 50 grain weight that came with another scale. I could give a rats patoot if the scale tells me the charge is 38.10 grains and a more accurate a scale would say 38.11 grains as long as I always get the same amount of powder time after time.

 

[normmatzen]

I have two old Ohaus TS 120 lab balances that need a 100gr and a 50 gr mass for caliberation which includes full scale and linearity.
As I am WAY more concerned with consistency and absolute accuracy not so important, I took two 100 gr masses and weighed both then polished the bottom of the heaviest one till both weighed exactly the same. Now, I calibrate both full scale and linearity with two identical 100g masses. And, they did not cost an arm and a leg! I also have a 200g and a 50g mass that are calibrated by the 100g masses.
I also bought a set of loading weights from Lyman or RCBS that have two 20gr, one 10 gr as well as some bent wire masses from 10gr to 1 gr or so for checking .

 

[dgeesaman]

I was about to order an F1 class calibration weight on ebay after watching a youtube video on scale calibration. Started thinking about it, does that really matter for our purposes since we all do load workup and look for signs of pressure along the way? It's really just a relative measurement as long as my scale is calibrated to the same physical weight every time, shouldn't matter if my calibration weight is 49.987g (my RCBS chargemaster weight) or 50.000g.

I could see the importance if loading to an exact known max charge right off the bat with no load development, but that's not how any of this works.

In a word, yes accuracy of the weight is irrelevant. You’re not comparing your balance to anyone else’s.

If there is a factor we care about it’s repeatability of the balance. I find it convenient to keep a 2g calibration weight around. This is much lighter than a typical calibration weight but at 30.8 grains it’s just right for a reloading check. Put it on the scale occasionally and make sure it always comes back to the same value.

 

[swadiver]

no

 

[dmoran]

By having a check weight, one will know from one day, week, month, year if your scale is reading the same.
While you may never have to recalibrate, you will only know that by checking (which I do every time I start a reloading session).

 

[Mastershot]

I have a two fx-120 scales with 419 powder scoop. The easiest way to tell when your scale is off is when you turn is on and reset to zero. I calibrate my scale with 100 gram weight and then rebooted the scale and recorded the the powder scoop and logged the weight on the side of it with a sharpie pen. So everytime I turn my scale on I can verify the scale if its off a little bit. Let me tell you after about a month of use its off now .02 grains now.

 

[BP1]

I bought a certified weight from Troemner..$$$

 

[LVLAaron]

As long as you use the same check weight, it doesn't matter how "accurate" the weight itself is. Just always use that weight.

 

[Tsu45]

You spent a fair bit of coin buying a decent balance. Why not purchase a good quality calibration weight set to go with it? Calibrating a balance with a weight whose actual/true weight is slightly off from the expected value may not affect the precision of the balance at all. It would affect the accuracy. However, as long as the calibration weight value was pretty close, you may well never notice anything. Nonetheless, why purchase a good balance and then cheap out on the calibration weight? That approach doesn't make a lot of sense to me.

Not concerned with the money. I just moved and set everything back up scale needed calibration so I started looking online for the process and they were using a class one weight. Got me thinking if it is really needed. Just thinking it isn’t relevant in the scope of reloading and curious what others thought.

 

[Tsu45]

Exactly how do you calibrate an fx120i?

Page 26

http://www.scalemanuals.com/andmanuals/fx-i-series-manual.pdf

 

[Ccrider]

Page 26

http://www.scalemanuals.com/andmanuals/fx-i-series-manual.pdf

Thanks

 

[Ranger188]

I received my scale about a month ago and wondered the same thing.
Called them and they said they include a 100g weight with it. It did come with one.
Checked it a couple times now and always is spot on.
The scale when you check calibration is for a 100g weight.

 

[Tsu45]

In a word, yes accuracy of the weight is irrelevant. You’re not comparing your balance to anyone else’s.

If there is a factor we care about it’s repeatability of the balance. I find it convenient to keep a 2g calibration weight around. This is much lighter than a typical calibration weight but at 30.8 grains it’s just right for a reloading check. Put it on the scale occasionally and make sure it always comes back to the same value.

I think that makes the most sense to calibrate closer to the range of typical reloading. Unfortunately on the FX120i it only has 50g and 100g options native to it. 100 is stock, changed mine to 50.

 

[Baer45]

You spent a fair bit of coin buying a decent balance. Why not purchase a good quality calibration weight set to go with it? Calibrating a balance with a weight whose actual/true weight is slightly off from the expected value may not affect the precision of the balance at all. It would affect the accuracy. However, as long as the calibration weight value was pretty close, you may well never notice anything. Nonetheless, why purchase a good balance and then cheap out on the calibration weight? That approach doesn't make a lot of sense to me.

I agree. One tip though...I bought mine from the scale company for nearly 100$ and found out somebody else bought a new one on eBay for around 40 or 50$...ugh!

 

[powderbrake]

The price of the calibration weight is proportional to it's tolerance. I checked for weight prices.
M2 100gram tol is +- .016 grams $17.30
Class 2 100 gram tol is +- .0005 grams $85.50
Class 3 100 gram tol is +- .001 grams $76.50

Note the Fx120 resolution is .001 grams. So you can spend $85 and have a weight that is better than your Fx120 scale, or $17 and have one that is 16 times worse than the scale...… but still accurate within .016/100.000 = .00016 or .016% of full scale. Which means you calibrated the scale to read 100g when there was only 99.984g on the scale. That doesn't sound like a big problem to me when I am reading .02 grains ( .308 grams) for one piece of Varget. Note the effect of 1 piece of Varget is 19 times the tolerance of the cheapest weight.
I am using the M2 weight sent to me when I bought my scale from Cambridge Enviro.