Mitchell makes a "Frequency Check Shaft" (US $24.95) that can be used to verify your machine's numbers. (Actually you are checking your machine's clamping system and clamping pressure, the electronics on a unit shouldn't give you any problems).
The shaft has a band/label 5" from the butt end. You are to clamp the shaft, ungripped, at the band and twang it to test your system. The shaft is calibrated to give 300 cpm +/- 1.
My system read 3 cpm too little, so I will adjust my frequency tables by 3 cpm. I use a 5" clamp, so no other computations were needed.
The specs on the shaft:
My complete unit is 41 3/4 inches overall with a weight of 389g.
The component parts are: 1. 256g tip weight with 1 1/2 inches of adjustment room (Mitchell must move the weight until they get their 300 cpm target). A set screw is used to hold the weight to the shaft. A fair sized dimple is transferred to the shaft, so you shouldn't lose the setting if you were to take it apart.
2. 133g 41 inch steel shaft. True Temper with 15 steps. First step at 12 inches.
This shaft provides a single measurement for a single beam length and a single clamp length. This seems fine with me. I do not know if the PCS calibration shaft provides any more data points or if there are any non linearity issues.
Mitchell can be reached at 800 437-1314
/Ed
