The potentiometer can function as a position sensor and the circuit can be properly adjusted. The potentiometer is best used as a voltage divider. The potentiometer can also act as a variable resistor, but there are some potential drawbacks. Do you know the difference between the two functions?
When acting as a voltage divider, the absolute resistance of the potentiometer does not affect the output voltage. The output voltage is proportional to the input voltage. Commonly used potentiometers have poor resistance accuracy and poor temperature coefficient. However, as long as the potentiometer has a uniform resistance, regardless of the resistance accuracy or temperature coefficient, 30% of the voltage will be obtained at 30%. Assuming that the slider is connected to a high-impedance circuit, the contact resistance of the slider does not affect the output voltage. The slider contact resistance is the resistance at the point of contact of the slider with the resistive element.
As shown in Figure 2, when the potentiometer acts as a variable resistor, its resistance accuracy and temperature coefficient will affect the circuit. The contact resistance of the slider affects the resistance of the circuit, and the contact resistance of the slider varies with position, temperature, vibration, and time.
Sometimes variable resistors are essential, and variable resistors can be designed with potentiometers that operate in proportional mode. The two circuits shown in Figure 3 have similar functions. Figure 3a uses P1 as a variable resistor to generate an inverted voltage in the output voltage of U1 that is linear with the potentiometer position. Since the resistance of P1 varies widely, gain adjustment is achieved by R3. In addition, the linearity and repeatability between the output voltage and the potentiometer position are affected by the contact resistance of the slider.
The operational amplifier U2 is introduced in Figure 3b so that the potentiometer operates in a proportional mode, thereby eliminating the drawbacks in Figure 3a. Operational amplifier U2 provides a high input impedance to reduce the effects of contact resistance. As the potentiometer position changes, the output voltage of operational amplifier U2 changes precisely from 0V to Vref. To provide an accurate voltage range for op amp U3, it is only necessary to set a fixed value for R5, R6, and no need to adjust the gain of the circuit.
Does your circuit require additional op amps or higher complexity in order for the potentiometer to operate in proportional mode? This is a tricky decision that you need to do. Sometimes it is unavoidable to use a potentiometer as a varistor. But by understanding the risk factors and sensitivities, you can choose a potentiometer to meet the desired performance. And you will know that you should pay special attention to possible problems when testing the certification circuit.
Metro Energy Feedback Transformer
Metro Energy Feedback Transformer,Dry-Type Power Transformer,Scb Power Transformer,Energy Feedback Transformer
SANON DOTRANSÂ Co., Ltd. , https://www.sntctransformer.com