Development of a standard rating for the Price pygmy current meter

Fifty new Price pygmy current meters, 50 used Price pygmy meters with used rotors, 50 used Price pygmy meters with new rotors, and 26 used Price pygmy meters with straight uniform (nonbeaded) contact wires were rated individually in a towing tank. A standard rating of V=0.961N+0.039 (V=0.293N+0.012), where V is the velocity in feet per second (metres per second) and N is the meter rotation in revolutions per second, was established for the group of new meters. Repeated ratings of two new meters showed that under the best rating conditions, the individual Price pygmy rating is repeatable to within 1 percent.

The standard errors of velocities predicted using the individual ratings and the standard ratings were compared. The use of the standard rating resulted in statistically higher standard errors than the individual ratings for all groups of meters. However, the differences are a fraction of 1 percent higher and are not of concern for practical purposes. The individual ratings and standard rating for the used meters with new straight contact wires were found to be statistically similar to the ratings for the new meters. Continuation of the use of individual ratings of Price pygmy current meters is probably unnecessary with the implementation of precise standards in their manufacture, rating of a random sample, and use.