These analogue output style transducers are available in three sizes: 1/4in (std.), 3/8in (high o/p) and 5/8in (heavy duty). They offer an inexpensive solution wherever a simple alternating waveform corresponding to movement past the pole piece is required. They are passive devices requiring no external power. They yield an output voltage in response to variations in their self-induced magnetic field caused by proximity to moving ferrous metal parts. They are steel encased for ruggedness and are supplied with two fixing nuts.
The output voltage is given for a load of 100kΩ with a 0.005in air gap at 20kHz operation. This corresponds quite closely to the pick up being 0.13mm from a 38mm diameter gear wheel with 30 teeth revolving at 13000rpm. The output will be different with other conditions and will be influenced by the composition of the gear wheel teeth. In unusual conditions it should be determined by experiment noting the following points:
Use the pick up with a high impedance load and position the pick up as close as is safe to the moving parts, clearances up to 2.5mm are quite normal
In a geared system, use the pick up with the highest speed gear wheel
