TCS900004, Rev.4
07/12/2016
Check us out at
www.TCSmeters.com
Page 14
Meter Calibration (Continued)
Making the Tests
Reset the register to zero, and run the required test quantity through the meter. Do not exceed the maximum
recommended rate of flow for the meter. Maximum and minimum recommended rates of flow for each 700 series
flow meter is marked on the meter identification plate and also in the maintenance manual.
Determining Test Results
Run the meter close to the mark on the indicator corresponding to the full prover capacity. Read the over or under
delivery in cubic inches, gallons or percent on the calibrated plate on the neck of the prover. If the plate is
calibrated in cubic inches, the percentage error can readily be computed on the following basis:
One gallon is equal to 231 cu.in.
Example: A 100
-
gallon prover holds 23,100 cu.in. Therefore, 23.1 cu.in. represents 0.1% error.
Meter Tolerance
In the United States, the National Institute of Standards and Technology, in NIST Handbook 44 specifies plus or
minus tolerances according to the following:
In Europe, the plus or minus meter tolerances are specified by OIML R117
-
1. In Canada, the plus or minus
tolerances are specified by the National Measurement Act.
Acceptance tolerances apply to new meters and repaired meters after reconditioning. Maintenance tolerances apply
to meters already in service. Special tolerances apply to meters in the United States only, for special instances as
determined by weights and measures officials.
Changing Meter Calibration
Refer to meter literature for method of changing meter calibration. Any change in the meter calibration adjustment
will change the delivery in the same amount for all rates of flow. That is, the calibration curve retains its shape, but
is moved up or down. Therefore, if a meter tests satisfactorily at full flow, but drops off too much at low flow,
changing the calibration will not remedy this condition; it will bring the low flow test to 100%, but it will also bring
the full flow above 100% by the same amount that the low flow was raised. A condition of this kind is caused either
by the metering system, need for meter cleaning or repairs, or because of an attempt to retain accuracy below the
minimum recommended rate of flow for the meter.
Repeatability
Consider the percentage error readings from each test run made at the same flow rate and draft size (calibration
run). The difference between the reading with the highest value and that with the lowest value must be less than a
value which is 40% of the applicable maintenance tolerance. For example, a meter in the USA, this would be
0.12% (0.30% x 0.4 = 0.12%). The percentage error of all test runs at each flow rate must still be within the
applicable tolerance.
Tolerance
Acceptance Test
Maintenance Test
Special Test
Repeatability
USA
-
Wholesale
+/
-
0.20%
+/
-
0.30%
+/
-
0.50%
0.12%
USA
-
Vehicle
+/
-
0.15%
+/
-
0.30%
+/
-
0.45%
0.12%
Indication of Device
Tolerance
Acceptance Test
Maintenance Test
Special Test
Repeatability
Europe
+/
-
0.30%
+/
-
0.50%
N/A
0.20%
Canada
+/
-
0.1875%
+/
-
0.375%
N/A
0.15%
Indication of Device
