Gempro 250 scale question

[Wolfdawg]

I have two Gempro 250 digital scales.

I keep them both plugged in and turned on. I have calibrated each. BUT, when I weigh anything on one and transfer it to the other for comparison, one of the scales is always .50 grains heavier.

When I put the item on my beam scale, it is "close" to one of the Gempro's, but not exact.

HOW DO I KNOW WHAT MY ACTUAL WEIGHT MEASUREMENT IS IF THREE SCALES SHOW SOMETHING DIFFERENT????????

Wolfdawg

 

[BoydAllen]

I would have someone with a lab quality scale that has been certified weigh something like a quarter, and keep that quarter in a container along with a note as to its correct weight, and a pair of tweezers to handle it with, so that it does not become coated with skin oil, and whatever that would attract and hold. You can use this as a standard to judge your scales. Also, I would contact the company that sold you the Gempro scales about this, and see what they will do for you. Did your scales come with calibration weights? Do they show similar results to what you have described, even after using the same weight to calibrate both scales?

 

[fguffey]

I have scales, I have the Ohaus 47 piece box of test weights. And then I have the lab type Ohaus 3 beam scales. I have test weights that do not agree, meaning I have to settle on 'A' test weight then make all of the scales agree with the test weight.

F. Guffey

 

[jlow]

The first question I have for you is how did you calibrate the scale? If you have only done a single point calibration with the supplied 20 gram weight, then the scale is only calibrated for that weight i.e. 20 grams. Unfortunately, we do not weight 20 gram of powder but usually a much smaller amount - for example, 40 grains of powder is only 2.59 grams. For the scale to be truly calibrated, you have to do both a single point with the 20 grams weight and a two point calibration with both a 20 gram and a 50 gram weight. There is a program on you scale to do both.

To understand why, think of a graph that represents the scale's range of measurements. If you only do a single point calibration, the line that represents how much you put on vs. what it detects can in fact pivot on that point and so.. On the other hand, if you use two points, then the line is locked down by two points and so the number of grains it reads vs. how many you put on is fixed.

 

[Egg]

While we are on the subject...where is the best place to purchase ACCURATE test weights?

 

[jlow]

We are not doing anything super critical and so a reasonably good one will work. You can get one from Amazon.

 

[C Valentine]

The first question I have for you is how did you calibrate the scale? If you have only done a single point calibration with the supplied 20 gram weight, then the scale is only calibrated for that weight i.e. 20 grams. Unfortunately, we do not weight 20 gram of powder but usually a much smaller amount - for example, 40 grains of powder is only 2.59 grams. For the scale to be truly calibrated, you have to do both a single point with the 20 grams weight and a two point calibration with both a 20 gram and a 50 gram weight. There is a program on you scale to do both.

To understand why, think of a graph that represents the scale's range of measurements. If you only do a single point calibration, the line that represents how much you put on vs. what it detects can in fact pivot on that point and so.. On the other hand, if you use two points, then the line is locked down by two points and so the number of grains it reads vs. how many you put on is fixed.

Where is the program on the GemPro to do the 2 point calibration? Cant find it. My Chargemaster does 2-point. 50 and 100 but cant find such an animal on the GemPro.

 

[Wolfdawg]

I only used the 20 gram weight that came with the scale.

I like the idea of having a quarter weighed on a REALLY good lab quality scale and using it as a standard.

I just don't know how to adjust one scale or the other to make them match what they are weighing. I will have to call Ole' Will Knot and find out what they suggest.

I appreciate all of the info!
Wolfdawg

 

[Dusty Stevens]

Most scales only calibrate to one or 2 points and those weights cannot be changed. A big set of calibration check weights is only good for verifying your scale doesnt read right- cant fix it

 

[BillPa]

Where is the program on the GemPro to do the 2 point calibration? Cant find it. My Chargemaster does 2-point. 50 and 100 but cant find such an animal on the GemPro.

Do the 'linearity' calibration first using the GPs 20 and the CM's 50 check weights then do the 20 or 50 span calibration.
https://www.youtube.com/watch?v=FBy50V3k1Ew

Bill

 

[jlow]

The first question I have for you is how did you calibrate the scale? If you have only done a single point calibration with the supplied 20 gram weight, then the scale is only calibrated for that weight i.e. 20 grams. Unfortunately, we do not weight 20 gram of powder but usually a much smaller amount - for example, 40 grains of powder is only 2.59 grams. For the scale to be truly calibrated, you have to do both a single point with the 20 grams weight and a two point calibration with both a 20 gram and a 50 gram weight. There is a program on you scale to do both.

To understand why, think of a graph that represents the scale's range of measurements. If you only do a single point calibration, the line that represents how much you put on vs. what it detects can in fact pivot on that point and so.. On the other hand, if you use two points, then the line is locked down by two points and so the number of grains it reads vs. how many you put on is fixed.

Where is the program on the GemPro to do the 2 point calibration? Cant find it. My Chargemaster does 2-point. 50 and 100 but cant find such an animal on the GemPro.

This gets asked so many times that I have saved my write-up. Follow this instruction to the letter and you will be OK:

Turn on the scale
Let it equilibrate for at least 30 min
To do the linear calibration do the following:

Hit the “Tare” button to zero the scale
Hit “Light”, then “Units” button each once in that order – the scale should now read “LinE”
Hit the “Tare” button again, the scale will now blink “0000” for a few seconds while it zeros itself
The display will change to “20.000” – this is your signal to put on the 20 gram weight
Leave it on until the display says “50.000” – this is your signal to take the 20 off and gently put on the 50
When the calibration is done, the display will show a steady “50.000” – your linear calibration is done.
Remove the 50 gram weight.

Follow this for the single point calibration do the following:
Hit the “Tare” button again to zero the scale
Hit the “Light” button once
Hit the “Tare” button once and the display will say “20.000”
Hit the “Tare” button one more time the display will say “0000” for a few seconds then “20.000”
This is your signal to put on the 20 gram weight
Wait a few seconds until the display stop blinking and say “20.000”
This means it has been calibrated.
Remove the 20 gram weight.
Now since the scale automatically change the units to grams to do calibration, you hit the “Units” button 4 times and it will change it back to grains – you are completely done.


Sounds complicated... Nope, you can do this in less than 30 seconds once you figure it out.

 

[gunnermhr]

While we are on the subject...where is the best place to purchase ACCURATE test weights?

McMaster Carr has whatever tolerance you want, I just bought one from them and it's really nice. 200Gram legal for trade was $40, they have one that's more accurate for $80 but I didn't see the need

 

[JRS]

Once you realize you are only masking a problem, take them to a business that calibrates scales.

Depending upon which beam scale you have, it could quite possibly be the most accurate of the three. Electronic scales (affordable scales) will never equal the long term accuracy and reliability of a good beam scale.

 

[jlow]

While we are on the subject...where is the best place to purchase ACCURATE test weights?

McMaster Carr has whatever tolerance you want, I just bought one from them and it's really nice. 200Gram legal for trade was $40, they have one that's more accurate for $80 but I didn't see the need

You need the 50 gram and not the 200 gram since that is what the linear calibration will ask you for.

 

[gunnermhr]

I bought the 200 Gram for a A&D GF300, not a GemPro, I'm sure I got the right thing for my application. The question wasn't which one to get but where to get a good test weight, maybe I shouldn't have given my example. I don't think the GemPro is a good option for weighing powder charges, I only used mine for cases and bullets, now I won't use it for that either. Probably do nothing more than. Collect dust at this point

 

[mr45man]

The gempro i have will /would never weigh to one kernel consistently.
Calibration did nothing for it.Also collecting dust at this point

Bought it when the DI 123 took a dive,


John H.

 

[jlow]

If you don't like it, don't use it.

Plenty of us thinks it is a great scale and so we use it.

LOL! It's just so predictable that the haters will always show their ugly head when a thread on the scale shows up. :

My advice, ignore them!

 

[gunnermhr]

I'm not a hater, I think its an excllent scale for the money, I just like/trust throwing powder charges with my 10-10 beam scale much better than the GemPro.

What I don't like, is when someone puts words in my mouth.

 

[ericbc7]

The gem pro works for me

I bought from Amazon check weights that can calibrate the Gempro totally.

Get the weights and do the linear calibration

 

[JRS]

If you don't like it, don't use it.

Plenty of us thinks it is a great scale and so we use it.

LOL! It's just so predictable that the haters will always show their ugly head when a thread on the scale shows up. :

My advice, ignore them!

I still use my early model Dillion. When the accuracy starts to limp a bit, I take it to the I&C department and have them re-calibrate it for me. When I need exact and repeatable weight, I use my Scott Parker tuned scale.