Suppose the worm gear of Figure 52 has a potentiometer attached as shown in Figure 53, so that the stem position is converted to resistance. A controller outputs a 4- to 20-mA signal, where 4 mA should correspond to minimum flow and 20 mA should correspond to maximum flow . Design a system so that comparators are used to activate the up or down terminals of the motor and drive the stem to the correct position required by the current. That is, suppose the controller outputs a current of 10 mA. This should cause the motor to move the stem to 1.5 cm.
(Hint: Convert the current to a voltage that is provided to two comparators.)
The reference terminals of the comparators have a voltage from a divider using the potentiometer connected to the worm gear. Be sure to include some hysteresis on the comparators.
