Most digital scales calibrate at a FULL SCALE value of 50 or 100 grams. With a stable zero, good environmental conditions, and repeatable readings at normal charge weights of a few grams, this is usually GOOD ENOUGH.
Unless you have some check weights close to your target charge you may have undetected linearity errors. The nice thing about scale linearity error is it's normally fairly constant over the life of the scale. About the same error today as next week, next year.
Got errors at small weights? CHEAT
HUH?
Calibrate @ 100 grams with a cal weight good to a few mg (ASTM Class 4). Check scale after cal and verify correct weight.
Now, test linearity at several points from a very low weight to full scale. Don't have all the weights to do that? Try one check weight that matters to your loads. Maybe a 5 gram test (ASTM Class 4 or better)? If you don't get 5.000g indicated you could have some linearity error where you use it the most. If it's constant and repeatable, no big deal. Get a couple (or few) counts of error at low weights, CHEAT with your full scale calibration.
HUH?
Two cases for cheating are presented.
You will need an accurate check weight near your most common load.
5 grams (about 77.16 grains) should work, and a small CHEAT weight of just a few mg (accuracy not needed).
5 gram reading is HIGH
Zero with no weight on the pan.
Add a few milligrams when you place the 100 gram cal weight on the pan. The scale will cal and read 100.000 grams with 100.010 grams on the pan. Remove all weights. After cal the 100 gram weight, by itself, will read light by 10 milligrams.
Smaller weights will read proportionally lower.
5 gram reading is LOW.
Zero with a small CHEAT weight (try 10 mg) on the pan.
Remove as you place the 100 gram cal weight on the pan. The scale will cal and read 100.000 gram. Remove the Cal weight but add the Cheat weight to complete the ZERO CAL . Use without the cheat weight (check your Zero). After cal the 100 gram weight, by itself, will read heavy by 10 milligrams.
Smaller weights will read proportionally higher.
Don't have a bunch of mg check weights? To cheat, just use a small piece of paper cut to about 10mg.
Unless you have some check weights close to your target charge you may have undetected linearity errors. The nice thing about scale linearity error is it's normally fairly constant over the life of the scale. About the same error today as next week, next year.
Got errors at small weights? CHEAT
HUH?
Calibrate @ 100 grams with a cal weight good to a few mg (ASTM Class 4). Check scale after cal and verify correct weight.
Now, test linearity at several points from a very low weight to full scale. Don't have all the weights to do that? Try one check weight that matters to your loads. Maybe a 5 gram test (ASTM Class 4 or better)? If you don't get 5.000g indicated you could have some linearity error where you use it the most. If it's constant and repeatable, no big deal. Get a couple (or few) counts of error at low weights, CHEAT with your full scale calibration.
HUH?
Two cases for cheating are presented.
You will need an accurate check weight near your most common load.
5 grams (about 77.16 grains) should work, and a small CHEAT weight of just a few mg (accuracy not needed).
5 gram reading is HIGH
Zero with no weight on the pan.
Add a few milligrams when you place the 100 gram cal weight on the pan. The scale will cal and read 100.000 grams with 100.010 grams on the pan. Remove all weights. After cal the 100 gram weight, by itself, will read light by 10 milligrams.
Smaller weights will read proportionally lower.
5 gram reading is LOW.
Zero with a small CHEAT weight (try 10 mg) on the pan.
Remove as you place the 100 gram cal weight on the pan. The scale will cal and read 100.000 gram. Remove the Cal weight but add the Cheat weight to complete the ZERO CAL . Use without the cheat weight (check your Zero). After cal the 100 gram weight, by itself, will read heavy by 10 milligrams.
Smaller weights will read proportionally higher.
Don't have a bunch of mg check weights? To cheat, just use a small piece of paper cut to about 10mg.
