Practicon's pr448 feeder controller

This article describes the pr448 feeder controller manufactured by Practicon Limited.

Description

The PR448 feeder controller controls constant ratefeeding from a weigh hopper mountedon load cells and fitted with a variable speed feeder. It supplies 10V DCexcitation to the load cells and amplifies and conditions the resultant signal toproduce a calibrated weight reading which it digitises to a resolution of65,000 divisions. From the reductionin this reading and from control and calibration data entered through its front panel, it accurately controls a 4-20m Aoutput signal to the variable speedfeeder, achieving pre-set target feed rate.To achieve accurate control immediately after start-up and during open loopcontrol, it stores a profile of feed rate against net hopper weight which itcontinually corrects during closed loop operation and which it uses both on start-up and during open loop operation.

Features

*Optimum feed rate stability in both high andlow feed rate applications.
*Stored feed rate profile.
*Batch quantity feed option.
*Suitable for both automatic and manualrefill applications.
*Serial Communications and Analogue input options.
*Low level and out-of-tolerance alarms
*Adjustable digital filtering for elimination of the effects of mechanical vibration.

The display may be selected to Actual Rate, Target Rateor Total at any time via the front panel keys. Accessto the control and calibration data is password number protected.

An additional 4-20mA output provides an actual feed ratesignal, to PLC/computer or remote display.

Alarms

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.

Refill

When the material in the hopper has dropped to a preset level it initiates the refill process by switching toopen loop control, and by setting a refill digital outputon. Alternatively, it can operate in applications where the hopper is manually filled by switching to open loop control whenever a sudden rise in weight occurs above apre-set control value.

Feeder with Automatic Refill

Analogue Remote Control Option

The PR448A provides an additional 4-20mA analogue input, which when configured will control the target feed rate.

Multidrop Serial Communications Option

The PR448M feeder controller provides an RS485 serial communications link for multiple feeder applications, a simple protocol using ASCII coded messages is used which is designed tobe easy to implement within a host PC or PLC system.Up to 32 PR448M units may be linked via a single twisted pair cable over a distance of up to 1000 metres.

The display may be selected to Actual Rate, Target Rateor Total at any time via the front panel keys. Accessto 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.

Batch Control

The feeder weighing controller may be used to control the feeding of a presetquantity of material, a digital output can be configured to a belt run function and together with start/stop digitalinputs provides the means of running the belt until the desired target quantity has been conveyed. The preset material target total may be entered via the keypad ordownloaded serially in the case of the PR448M version.

Technical Data

*Model No:Model PR448 BasicModel PR448A Analogue Remote ControlModel PR448M Multidrop Serial CommsAdd ‘D’ for DC power option eg PR448-D
*Power Supply:Universal fused power supply 85-264V ACor 9-36V DC (eg PR448-D). Internal MainsFuse fitted. Power consumption 10VA
*Load Cell Excitation:10V DC @ 125mA max, 1 to 4 x 350 ohmload cells may be connected in parallel.
*Load Cell Input Range:0-20mV min, 0-2.5V max.Filter adjustable 0.2 to 20Hz.
*Weighing Accuracy:Up to 16,384 +/-0.5 divisions.16 bit 1:65,000 internal resolution.
*Analogue Output:4-20mA ActiveRelay Outputs:240V AC or 30V DC 5A rated.
*Enclosure:Panel mounting DIN case 144mm wide x96mm high x 132mm deep.IP65 sealed front panelPanel Cut-out 138mm wide x 92mm high
*Environment:Operate 0-50C, 20-80% RH non-condensing. Storage -40 to 80C

Practicon Limited

Email: sales@practicon.co.uk Website: www.practicon.co.uk