What is a common potential solution to interference caused by a radio system on the tachometer of a building's elevator circuit?

Adding a 0.01 μF capacitor across the motor leads is a common and effective solution for reducing radio frequency interference (RFI) that can affect the operation of devices like a tachometer in an elevator circuit. This capacitor acts as a bypass or decoupling capacitor, which helps shunt high-frequency noise to ground. By doing so, it reduces the amount of electromagnetic interference that can couple into the tachometer from the motor, ensuring that the tachometer receives a cleaner signal for accurate speed measurement.

In the context of elevator systems, this approach is favored for its simplicity and efficiency, avoiding more invasive or costly solutions such as completely replacing system components. Interference can be a co-product of the motor’s operation due to its electromagnetic characteristics; thus, incorporating a capacitor to filter out high-frequency noise directly at the source is typically a practical response to such issues.