Mich. Admin. Code R. 460.3612

Current through Vol. 24-10, June 15, 2024

Section R. 460.3612 - Test standards; accuracy

Rule 612.

(1) The accuracies of all primary reference standards must be certified as traceable to the National Institute of Standards and Technology (NIST) or National Research Council (NRC) Canada, either directly or through other recognized standards laboratories. These standards must have their accuracy certified at the time of purchase. Standard cells must be intercompared regularly and at least 1 standard cell be checked by a standardizing laboratory at intervals of not more than 2 years. Reference standards of resistance, potentiometers, and volt boxes must be checked at intervals of not more than 3 years.

(2) Secondary watthour meter standards must not be in error by more than plus or minus 0.3% at loads and voltages at which they are to be used, and must not be used to check or calibrate working standards, unless the secondary standard has been checked and adjusted, if necessary, within the preceding 6 months. Each secondary standard watthour meter must have calibration data available and have a history card.

(3) Secondary standards indicating instruments must not be in error by more than plus or minus 0.5% of indication at commonly used scale deflection and must not be used to check or calibrate portable indicating instruments, unless the secondary standard has been checked and adjusted, if necessary, within the preceding 12 months. A calibration record must be maintained for each standard.

(4) Regularly used working portable standard watthour meters must be compared with a secondary standard at least once every 6 months. Infrequently used working standards must be compared with a secondary standard before they are used.

(5) Working portable standard watthour meters must be adjusted so that their percent registration is within 99.7% and 100.3% at 100% power factor and within 99.5% and 100.5% at 50% lagging power factor at all voltages and loads at which the standard may be used. A history and calibration record must be kept for each working standard.

(6) The meter accuracies required in this rule for all primary, secondary, and working standards must be referred to 100%. Service measuring equipment must be adjusted to within the accuracies required assuming the portable test equipment to be 100% accurate with the calibration correction taken into consideration.

Mich. Admin. Code R. 460.3612

1983 AACS; 1995 AACS; 2008 AACS; 2023 MR 7, Eff. 4/10/2023