• 1 mg to 5 kg weights.  Sold individually or as a 9-piece or 21-piece set.
• All weights meet or exceed ASTM specifications
• All mass measurements are made using procedures developed by NIST
• All mass standards are milled from the finest corrosion-resistant stainless steel stock ensuring consistent density
• Each weight is calibrated by a NVLAP-accredited metrology lab in a climate-controlled environment
• One-piece construction provides the maximum mass stability
• Each weight and weight set is supplied complete with a Certificate of Traceability
• Certificate of Calibration
  

Nominal Value	Class	Part Number	Report of Traceability	Certificate of Calibration	Tolerance	Price
Small Knob Style, ASTM Shape
100 g	Ultra Class U	WT100GCLSUC	YES	YES	±0.125 mg	$109.00
100 g	Class 1	WT100GCLS1C	YES	YES	±0.25 mg	$94.00
100 g	Class 2	WT100GCLS2C	YES	YES	±0.50 mg	$89.00
50 g	Ultra Class U	WT50GCLSUC	YES	YES	±0.060 mg	$99.00
50 g	Class 1	WT50GCLS1C	YES	YES	±0.12 mg	$89.00
50 g	Class 2	WT50GCLS2C	YES	YES	±0.25 mg	$84.00
The weight value can deviate above or below the nominal value by the tolerance defined.  To determine the tolerance of a mass, look at the denomination or nominal value of the weight and the appropriate class you need.
Custom weight sets are available upon request by calling Precision Weighing Balances at 978-521-7095
All calibration weights are not returnable.  Once your order has been placed it CAN NOT be cancelled.  Please carefully consider this prior to placing your order.  The reason for this is these weights are custom manufactured and are certified on the date they were made.  In addition, if you touch the calibration weight with your fingers the oil in your skin would change the tolerance and we can not take this chance if the weight was returned.

• Uncertainty value
• Identifying number
• NIST test number
• Date the standards were last calibrated
• NVLAP laboratory code

• Single weights - $65
• Two or more weights - $48 each
• Weight sets of 15 or more weights - $37 each

Please call us at 978-521-7095 if you presently have calibrations weights that require recertification.

What does calibration of a laboratory weight entail?

Sartorius mass comparators compare a weight to a known mass (a NIST calibrated reference weight) and report the difference, to a very small value.  These mass comparators can ascertain and measure differences to 10, 1, and even 0.1 micrograms (one ten-millionth of a gram), multiple weighings, averaged, can resolve the differences to even smaller amounts.  

Calibration technicians must wear appropriate static free clothing, as well as gloves, hair nets and face masks, to reduce the possibility of contamination (and changing the weight of the weights) from skin oils, hairs, or airborne droplets.  Calibration weights are never touched directly by human hands. 


What is the difference in tolerance between Sartorius Ultra Class U, Class 1, Class 2 and other calibration specifications?

Metric Weight Tolerances - all tolerances stated in milligram (mg)
	American Society of Testing & Measurement ASTM E617
Denomi- nation Metric	Sartorius Ultra Class U	Class 1 mg	Class 2 mg	Class 3 mg	Class 4 mg	Class 5 mg	Class 6 mg	Class 7 mg
5 kg	6.00	12	25	50	100	250	500	1400
3 kg	3.80	7.5	15	30	60	150	300	1000
2 kg	2.50	5.0	10	20	40	100	200	750
1 kg	1.25	2.5	5.0	10	20	50	100	470
500 g	0.600	1.2	2.5	5.0	10	30	50	300
300 g	0.380	0.75	1.5	3.0	6.0	20	30	210
200 g	0.250	0.50	1.0	2.0	4.0	15	20	160
100 g	0.125	0.25	0.50	1.0	2.0	9	10	100
50 g	0.060	0.12	0.25	0.60	1.2	5.6	7
30 g	0.037	0.074	0.15	0.45	0.90	4.0	5	44
20 g	0.037	0.074	0.10	0.35	0.70	3.0	3	33
10 g	0025	0.050	0.074	0.25	0.50	2.0	2	21
5 g	0.017	0.034	0.054	0.18	0.36	1.3	2	13
3g	0.017	0.034	0.054	0.15	0.30	0.95	2	9.4
2 g	0.017	0.034	0.054	0.13	0.26	0.75	2	7.0
1 g	0.017	0.034	0.054	0.10	0.20	0.50	2	4.5
500 mg	0.005	0.010	0.025	0.080	0.16	0.38	1	3.0
200 mg	0.005	0.010	0.025	0.060	0.12	0.26