R6‑26 TEST PROCEDURES AND ACCURACIES
(a) Meters and/or associated metering devices shall be tested at the points and adjusted to the tolerances prescribed below. The test of any unit of metering equipment shall consist of a comparison of its accuracy with the accuracy of a standard. The Commission will use the applicable provisions of the standards listed in Rule R6‑21 as criteria of accepted good practice in testing meters.
(b) Positive Displacement Meters.
(1) Accuracy at Test Points.
Flow Adjusted to within
Check flow 98.5%-100.5%
Not less than full
rated flow 98.5%‑100.5%
(2) Overall Accuracy. - The accuracy at check flow and the accuracy at not less than open rated flow shall agree within one percent.
(c) Orifice Meters. - Accuracy at test points must be within 1/2%, plus or minus.
(d) Timing Devices. - All recording type meters or associated instruments which have a timing element that serves to record the time at which the measurement occurs must be adjusted so that the timing element is not in error by more than plus or minus 4 minutes in 24 hours.
(1) All meters and/or associated metering devices, when tested, shall be adjusted as closely as practicable to the condition of zero error.
(2) All tolerances are to be interpreted as maximum permissible variations from the condition of zero error. In making adjustments no advantages of the prescribed tolerance limits shall be taken.