This is accompanied by enclosing a linear potentiometer in a special cover tube on the actuator. The potentiometer is an infinitely variable membrane type device. An excitation voltage is applied to it and read by a voltage sensing circuit such as a voltmeter. A wiper is attached to the ball nut and translates along the length of the potentiometer. As the wiper moves, the voltage received by a voltmeter varies accordingly.
The potentiometer has three leads. An excitation DC voltage is applied to the red lead. The black lead is the ground at 0 VDC. The white lead gives an output DC voltage signal that varies linearly with the position of the actuator.
It is usually simplest to select an excitation DC voltage that is an even multiple or divider of the actuator’s stroke. For example, if the actuator in the application has a 6 inch stroke, select an excitation voltage of say 6 or 12 volts. This allows easy scaling of the voltage. The actuator motor and the potentiometer power should be completely independent from each other to avoid noise problems.
The power rating for the potentiometer is 1 watt maximum. Mechanically, the device is capable of 1 million cycles and will operate over a temperature range of -45°C to 75°C.
The linear potentiometer is provided only as a method of measuring the actuator’s position. It is left to the user to provide a method of reading the signal, interpreting the signal and devising a control scheme for the particular application.
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