FREQUENCY OUTPUT

A frequency output is useful when a simple interface is needed to a computer or PLC that can measure frequency directly. The output is generally a logic level rectangular wave or an open collector transistor. The open collector transistor is often part of an optically isolated integrated circuit.

The simplest wave shape to create is a constant width pulse that varies in repetition rate proportional to the input signal.

A symmetrical square wave can be created, but the circuitry is slightly more complex and costly.

Sine wave output can also be also be created with a more complex circuitry.

If noise pickup between the output and the load is a consideration due to cable length and routing, a balanced output can be provided to help eliminate noise through common mode rejection capability.

The key factors that determine overall cost of the output circuitry include: