1 milligram - 100 gram twenty-one (21) piece Class 1 calibration weight set
(PWB7228-1W), includes NVLAP Certificate of
Calibration to Class 1 tolerance. Typical lead time is 7 to 10 business days from the date order
is placed to shipping from NVLAP metrology lab.
These Metric Precision Weight Set weights are appropriate for calibrating high-precision
toploading balances with readabilities ranging from 0.001g to 0.01g.
Single-piece construction: Weights 500 mg and below are 1 piece construction with no adjusting cavity with one end turned up for easy handling. Weights above 500 mg are 2 piece construction with handling knob.
Highly polished weights: 100g-1g weights are stainless steel, 500 mg down to 50mg weights are stainless steel, weights below 50mg are flat aluminum weights.
Flat
weights in the 1mg to 500mg range and knob-style weights.
1mg-100g
Class
1
PWB7228-1W
NO
YES
1mg-100g
Class
2
PWB7228-2W
NO
YES
1mg-100g
Class
1
PWB7228-1T
YES
NO
1mg-100g
Class
2
PWB7228-2T
YES
NO
Weights
Included: 1mg, 2 x 2mg, 5mg, 10mg, 2 x 20mg, 50mg, 100mg,
2 x 200mg, 500mg, 1g, 2 x 2g, 5g, 10g, 2 x 20g, 50g, 100g
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.
Weight sets consist of flat weights
in the 1mg to 500mg range and knob-style weights.
Certificate of Calibration
Certificate of Calibration are available for any Ultra Mass, Class 1, or Class 2 weight or weight set. The "W" at the
end of the part number designates a Certificate of Calibration will
be included with your weight(s). The Certificate of Calibration
includes everything found in a Report of Traceability listed above
with the additional information listed below:
Uncertainty value
Test conditions temperature, barometric pressure, humidity.
Conventional Mass Correction
Uncertainty of the measurement
Identification of the balance used in the calibration
as found value if an adjustment is performed
assumed density of the weight
material weight is made from
Pass/Fail result of magnetic testing
Volume of the weight
Cubical Coefficient of expansion
True Mass correction
Who do you feel needs a Calibration Certificate
verses Report of Traceability?
If you are under ISO, FDA or other regulation they should get a Calibration
Certificate. Also, anyone that plans to calculate uncertainty for their own
process would need the certificate of calibration so they could correctly
include our uncertainty into their own uncertainty budget.
If they have a balance or scale with the ability to read to a milligram or better it is always recommend they know the corrected value of the weight and this is only available with the Calibration Certificate.
Recertification Service Weight values can change over time due to scratches, fingerprints,
wear and even corrosion resulting from atmospheric contaminants.
Regular checks on the accuracy of mass standards ensures the accuracy
of measurements. We have access to mass metrology lab providing
this service at a very competitive prices.
The rates vary depending upon the size of the weight (1 gram cost less than a 5kg weight) are listed below and subject to change.
Typical turn around time (excludes transit time) is 7 to 10 business
days upon receipt at the metrology lab. You
are responsible for both in and out bound freight and insurance
costs.
Single weights - 1g - $44 , 5kg - $144
Weight sets depend upon the amount of weights in a set - 21 piece set 1mg - 100g - $854
Please call us for up to date pricing and the procedure involved in sending your weights in for recertification.
What does calibration of a laboratory weight entail?
All calibrations are accredited calibrations performed using weights by NIST weighing designs, where
all weights are compared against 2 standards. The mass comparators used for performing the calibration ascertain and measure differences to 10, 1,
and even 0.1 micrograms (one ten-millionth of a gram). The
value of the unknown weight is computed using a least sum squares
technique by the NIST masscode software. The software performs
stastical checks on the balance performance and the computed values
of the second standard. If the balance performance or computed
value of the second standard are found to be unacceptable the software
requires that the measurement be repeated. It is only when
the process standard deviation and computed value of the check standard
are acceptable that metrologist is confident in the value for the
customer's weight. All measurements in metrology laboratory,
including tolerance testing, use this Echelon I weighing technique.
The weighing designs are the same ones developed and used by NIST.
All measurement results are traceable to the International Prototype
Kilogram (IPK) through a NIST calibration of our primary standards.
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 True Mass Correction?
Basically, the only people who use "True Mass" are
calibration laboratories and other people who apply air buoyancy
corrections to the measurements. Conventional mass is what a weight would weigh at sea level at standard
temperature and pressure. Since most people use their weights in air and
don't have the equipment or desire to measure and calculate the air density
they have no need for the true mass values. NVLAP published NIST Handbook
150-2G requiring calibration certificates to reporting "true mass". If someone needs true mass they typically will know how to calculate it from the
Conventional mass.
What is Uncertainty?
Uncertainty is more than just the repeatability of the balance it is a
summation of all things which contribute to the error in the measurement
process. Uncertainty is the root sum square of balance deviation, repeatability on
the check standard, variability in the density of the standard, variability
in the density of the weight under test, variability of the temperature,
variability of the barometric pressure, variability of the humidity,
operator skill and the uncertainty of the standard used multiplied by two.
What is the difference in tolerance between Ultra,
Class 1, Class 2 and other calibration specifications?
Metric
Weight Tolerances - all tolerances stated in milligram (mg)
American
Society of Testing & Measurement ASTM E617
International
Organization of Legal
Metrology Recommendation R111
Denomi-
nation
Metric
Ultra Class
Class
1
mg
Class
2
mg
Class
3
mg
Class
4
mg
Class
5
mg
Class
6
mg
Class
7
mg
E1
mg
E2
mg
F1
mg
F2
mg
M1
mg
M2
mg
M3
mg
5
kg
6.00
12
25
50
100
250
500
1400
2.5
7.5
25
75
250
750
2500
3
kg
3.80
7.5
15
30
60
150
300
1000
2
kg
2.50
5.0
10
20
40
100
200
750
1.0
3.0
10
30
100
300
1000
1
kg
1.25
2.5
5.0
10
20
50
100
470
0.5
1.5
5
15
50
150
500
500
g
0.600
1.2
2.5
5.0
10
30
50
300
0.25
0.75
2.5
7.5
25
75
250
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
0.1
0.30
1.0
3.0
10
30
100
100
g
0.125
0.25
0.50
1.0
2.0
9
10
100
0.05
0.15
0.5
1.5
5
15
50
50
g
0.060
0.12
0.25
0.60
1.2
5.6
7
0.030
0.10
0.30
1.0
3.0
10
30
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
0.025
0.080
0.25
0.8
2.5
8
25
10
g
0025
0.050
0.074
0.25
0.50
2.0
2
21
0.020
0.060
0.20
0.6
2
6
20
5
g
0.017
0.034
0.054
0.18
0.36
1.3
2
13
0.015
0.050
0.15
0.5
1.5
5
15
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
0.012
0.040
0.12
0.4
1.2
4
12
1
g
0.017
0.034
0.054
0.10
0.20
0.50
2
4.5
0.010
0.030
0.10
0.3
1.0
3
10
500
mg
0.005
0.010
0.025
0.080
0.16
0.38
1
3.0
0.008
0.025
0.08
0.25
0.80
2.5
200
mg
0.005
0.010
0.025
0.060
0.12
0.26
1
1.8
0.006
0.020
0.06
0.20
0.6
2
100
mg
0.005
0.010
0.025
0.050
0.10
0.20
1
1.2
0.005
0.015
0.05
0.15
0.5
1.5
50
mg
0.005
0.010
0.014
0.042
0.085
0.16
0.5
0.88
0.004
0.012
0.04
0.12
0.4
20
mg
0.005
0.010
0.014
0.035
0.070
0.12
0.5
0.56
0.003
0.010
0.03
0.10
0.30
10
mg
0.005
0.010
0.014
0.030
0.060
0.10
0.5
0.4
0.002
0.008
0.025
0.08
0.25
5
mg
0.005
0.010
0.014
0.028
0.055
0.080
0.2
0.002
0.006
0.020
0.06
0.20
2
mg
0.005
0.010
0.014
0.025
0.050
0.060
0.2
0.002
0.006
0.020
0.06
0.20
1
mg
0.005
0.010
0.014
0.025
0.050
0.050
0.1
0.002
0.006
0.020
0.06
0.20
The
table above is a listing of the tolerances of various classes
of masses. 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.