The PR448 Feed Rate Controller operates in conjunction with continuous loss-in-weight feeders in order to accurately control the rate of delivery of product from a weigh hopper. The loss-in-weight feeder weigh hopper is mounted on load cells and is fitted with a variable feeding device such as a variable speed screw or vibratory feeder.
The PR448 Feed Rate Controller connects with up to four strain gauge load cells. It supplies 10V DC excitation to the load cells and using a combination of high resolution electronics coupled with intelligent signal filtering techniques conditions the resultant signal to produce a calibrated weight reading. From the reduction in this weight reading during feeding the PR448 Feed Rate Controller continually calculates the rate of feed of material fed from the weigh hopper and the total quantity of material discharged.
Using a comparison of this calculated rate of feed against the desired rate the PR448 Feed Rate Controller uses a sophisticated control algorithm to make adjustments to the 4-20mA analogue output control signal, used to control the variable feeding device, in order to maintain a pre-set target feed rate. User configurable control parameters allow the PR448 Feed Rate Controller to be tuned to the loss-in-weight feeder and material flow characteristics.
To achieve accurate control immediately after start-up and during periods of volumetric control, it stores a profile of feed rate against net hopper weight which it continually corrects during gravimetric operation and which it uses both on start-up and during volumetric operation.
The display may be selected to Actual Rate, Target Rate or Total at any time via the front panel keys. Access to the control and calibration data is password number protected.
An additional 4-20mA output provides an actual feed rate signal, to PLC/computer or remote display.
Two alarm digital outputs are provided, one for low hopper weight alarm and the other for out of tolerance feed rate or refill rate alarms.
When the material in the hopper has dropped to a pre-set level it initiates the refill process by switching to volumetric control, and by setting a refill digital output on. The hopper is then refilled and the gravimetric loss-in-weight operation resumes. Alternatively, it can operate in applications where the hopper is manually filled by switching to volumetric control whenever a sudden rise in weight occurs.
If you are using a host PLC or PC system that acts as the central point for the transmission of the desired target feed rate for each individual loss-in-weight feeder then you have the option of interfacing to each PR448 Feed Rate Controller either by 4-20mA analogue signals or serial communications using the supported SABus (simple ASCII commands) protocol in order to both set the target feed rate within each individual PR448 Feed Rate Controller and receive the live feed rate data back from each controller.
The PR448 Feed Rate Controller may be used to control the feeding of a pre-set quantity of material, with or without rate control, for batching and loading system. A digital output operates as the run signal to the feeding device and together with start/stop digital inputs provides the means of running the feeder until the desired target quantity of material has been discharged from the weigh hopper. The pre-set material batch target may be entered via the keypad or downloaded serially.
PR448 - Analogue Interface Feed Rate Controller Data Sheet
The PR446 Belt Feeder Controller is used within weigh belt feeder systems in order to accurately control the rate of delivery of bulk solid materials along a conveyor belt. It can be used to control the belt speed on weigh feeders where the belt loading is constant or pre-feeding devices onto a fixed speed belt. […]