The PC320 Process Controller is reliable, accurate, and suitable for measuring any type of 2 and 3 wire sensors with 4-20 mA, 0-1 volt, and 0-5 volt outputs. The process controllers come pre-programmed for use with 12 different common sensor types and appropriate selectable engineering units. In addition you can program the PC320 process controllers to monitor any type of custom sensor in any units you define. Custom user defined engineering units are also programmable for all of the process controller's standard sensor types. Both 2-point and 3-point calibration methods are supported by the process controllers and an additional 3rd order polynomial equation can be applied to the sensor data to correct for non-linearities in sensor output. The process controller's polynomial mode is useful for calculating other parameters based on a non-linear sensor reading such as calculating water flow rate from water level.
Process Controller Display and Outputs
The process controller's LCD shows what type of sensor is being monitored, the data reading averaged over a user programmable time period, and the engineering units selected. The display also shows the current On or Off state for each of the process controller's 4 relays. Two other display modes are available on the PC320 process controllers. One shows the maximum and minimum process controller sensor readings since last reset. Another mode displays the current state of any of the process controller's 4 relays in real time, the sensor reading that caused the last triggering event, and the On or Off time remaining in the control cycle. The process controller's LCD can be backlit for easy viewing at all times and offers a power saving mode for limiting current drain in battery powered applications.
Process Controller Outputs
Four relays are provided by the PC320 process controllers for controlling external devices including samplers, alarms, mixers, pumps, control valves, floodgates and telemetry systems. Each of the process controller's relays are independently programmable to trigger on maximum and/or minimum threshold levels in one of five different control modes. Relay operation is defined by setting upper and lower sensor threshold levels and turning relays on when the process controller's sensor reading exceeds a normally defined range. Both normally open and normally closed relay contacts are provided by the process controllers. The process controller's relay modes include a One Time trigger that will engage a relay one time only for a programmed on time period when a sensor reading falls outside of a defined normal range. The Steady state mode will turn on a relay as long as the process controller's sensor reading is out of the normal range. The Cyclic mode will continually turn a relay on and off for user definable on and off times while the process controller's sensor reading is outside of normal range. Additionally, High Control and Low Control Modes are also provided the process controllers. These modes are used by the process controllers for maintaining a sensor reading within a specific range; for example keeping the water level in a tank between two predefined levels. A sixth process controller relay mode allows a relay to be deactivated regardless of settings. There are also programmable Delay Times and Hysteresis available for the process controllers. Setting a Delay Time will delay a process controller's relay from turning on for that amount of time when a sensor reading falls outside of normal range. This is used to limit the effect of rapidly changing sensor readings and keeping the process controller's relays from reacting quickly to very small changes near a threshold setting. The process controller's Hysteresis function allows the relay to remain on until the sensor reading falls into the normal range again, plus a defined hysteresis percentage. This also prevents the process controller's relays from overreacting to rapidly changing events near a threshold level. A test mode is provided for manually testing the process controller's relay operation. A fully scalable 4-20mA output is available for recording the process controller's sensor data readings by devices like data loggers, PLC's, telemetry systems, and chart recorders.