Section 460.3612. Test standards; accuracy.

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

(2)   Secondary watthour meter standards shall not be in error by more than plus or minus 0.3% at loads and voltages at which they are to be used, and shall 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    shall    have calibration data available and shall have a history card.

(3)   Secondary standards indicating instruments shall not be in error by more than plus or minus 0.5% of indication at commonly used scale deflection and shall 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 shall be maintained  for each standard.

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

(5)    Working portable standard watthour meters shall 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 shall be kept for each working standard.

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

History: 1983 AACS; 1995 AACS; 2008 AACS.