Woodward 82510 Magnetic Pickups and Proximity Switches for Electronic Controls

The magnetic pickup is available in short or long standard models, a standard metric model, hazardous duty models, and explosion-proof models, including CSA/ATEX approved models (see Figure 1-3 for dimensions and part numbers).

Mount the magnetic pickup radially to the outside diameter of the desired gear, either through a housing or on a rigid bracket. Make sure the gear is of magnetic material. The gap between the pickup and the outside diameter of the gear should be set normally between 0.25 mm and 1.02 mm (0.010 inch and 0.040 inch) at the closest point. Ensure the gear has less than 0.51 mm (0.020 inch) diametric runout.

Since the signal strength is inversely proportional to gap distance, a weak signal may be generated with more than 1.02 mm (0.040 inch) gap. A shield of non-magnetic material may be installed between the gear and the pickup if necessary for physical shielding. Since this material spaces the pickup face farther from the gear, and since an electromagnetic force may be generated by eddy currents in the shielding material, make sure the signal level is still high enough to operate the speed signal circuit.

Most electronic controls require a minimum output of 1.5 V (ac, rms) from the magnetic speed pickup at the lowest controlling speed. Figures 1-4 and 1-5 show the maximum air gap allowed for each surface speed and diametral pitch or gear module to produce this minimum required voltage.