In today’s world there are many ways of controlling a piece of equipment, i.e. a generator voltage or a conveyor speed. Depending on your setup and your equipment it can be a requirement to provide a voltage signal like 0-5VDC from minimum to maximum range or an actual resistance. In the example of the voltage regulator in a generator, there can be the capability of regulating the voltage ±5% with the 0-5VDC signal. In such case you would want to provide the voltage signal and be done with it, right? Well maybe you should consider some “what-if” cases. First in 99% of the time an electronic potentiometer (MXR845DI2 or T7900) would do just fine, they are adjustable to how fast, how far, and how accurate they should be in their regulations. They are compact, and do not require complicated programming, only a laptop and a traveling tech can handle. But what-if you have a aux power outage, what will happen to your generator voltage? Will it go to nominal voltage, drop to -5% or stay put where it was left? Where will the signal be what aux supply is returned? Down the same alley what if the electronic potentiometer fails, how will your system be affected.
Then there is a true Motorized Potentiometer (E7800) where a small motor with a clutch which turns a real potentiometer. It will not give you the 0-5VDC signal, but that is already available in the AVR (Automatic Voltage Regulator) so +5VDC in on the high side of a 20KΩ 2Watt potentiometer, and 0VDC on the low side, and the wiper becomes your 0-5VDC signal. The speed is adjustable and easy for a user to interact with. Now the what-if. You have a aux power loss – the potentiometer will not turn, but it will stay where it was left off, and so the voltage will not change. If the potentiometer breaks will the AVR be supplied with 5VDC or 0VDC, and how will that affect your complete installation.
Electronic potentiometers are great for installations where aux supply is solid, or if lost the generator stops, so no over or under voltage problems occur. A motorized potentiometer is perfect if the generator need a continued signal even if loss of aux supply, but they do require maintenance of the potentiometer itself, as they tend to wear.
We hope you have enjoyed this article, and if you need to discuss some of these issues with us, please reach out to us. #SELCOUSA