††††† Selection of the proper Al-Tek magnetic sensor may require the calculation of sensor output voltage to assure proper operation in your specific application. To assist in this area, let us consider the following typical application: Requirement is speed display with overspeed and underspeed control as well as 4-20 mA signal to a PLC. Speed range is 0-3600 RPM with low speed set point at 300 RPM, available shaft diameter for mounting a gear is 2.000 in. and a .030 in. air gap is ideal.
††††† You have selected a Tachtrol 30, P/N T77630-10, with a 60T steel, split gear, P/N G79870-202-1901, and you are considering to use sensor P/N 70085-1010-001. The question is if the sensor has enough output voltage at 300 RPM.
We can list the following parameters:
a.) Tachtrol 30: Load impedance - 12k-ohms
†††††† Sensitivity - 200 mV peak
b.) Split gear: Outside dia. - 5.166 in.
†††††††††††††††††††† D.P. - 12
††††††††††††††† † †† No. of Teeth - 60
†††††† Standard output voltage - 40V (P-P) min.
†††††† Guarantee Point - 3.4V P-P min.
†††††† D.C. Resistance - 130 ohms max.
†††††† Typical inductance - 33 mH ref.
††††† The final adjusted value is 386 mV peak.
††††† As stated earlier, the sensitivity or threshold of the Tachtrol 30 is 200mV peak at the stated conditions, the selection of P/N 70085-1010-001 is acceptable.
††††† By setting up ratios, you can determine that the minimum sensed speed is 155 RPM.
††††† If the final value of Ec had been slightly less than 200 mV, a reduction of the air gap (from .030î to .025î) would boost the output above 200 mV.
††††† If it should be determined that the required sensor cannot be selected from the catalog models, the best procedure is to compile a list of all your requirements and contact your area distributor to assist you in the selection of the correct sensor.