The High-Speed discrete inputs can be configured to measure the amount of time between pulses. When you want a scaled value representing a speed or rate, the high-speed input timer is a better option for pulse rates below 5 kHz. This is compared to using the high-speed input pulse counting selection.
The BRX Do-More series of programmable logic controllers have built-in high-speed inputs. These inputs can function in Counter, Timer, or Pulse Catch modes. Every CPU will have either 6 or 10 high-speed inputs (HSI) available depending on the model. These inputs can be used for input frequencies from 0 to 250Khz. 250Khz represents 250000 input counts per second that can be coming from devices connected to your PLC like an encoder. Due to the speed of the inputs, they function on the BRX Do-More PLC asynchronous with the PLC scan time.
We will continue looking at the high-speed inputs on our BRX Do-More PLC, by looking at the pulse timer mode. Previously we looked at the high-speed count mode of the PLC. We scaled the count to display RPM (Revolutions per Minute). Scaling the edge trigger timer from our incremental encoder, we will scale and compare the RPM from last time. Let’s get started.