Scanning Devices Loadcell Controllers

Loadcell Controllers operate with bridge-style, strain gage type transducers in force and weight measurement applications. They provide loadcell excitation, signal amplification, analog - to - digital conversion and scaling to engineering units. Setup and output depends on the controller and application.

PC/104 and ISA controllers are designed to be PC peripherals. They require a PC program for calibration and setup. But once setup, they operate without PC intervention, taking measurements, responding to digital inputs and setting/clearing digital outputs as specified by setup parameters. They may, at the PC program's request, transfer data for use in the PC program. Program libraries and sample programs in "C" and Q-Basic are available to illustrate application techniques and to provide installation verification.

Stand-alone controllers are equipped with numerical display and programming keys. They may be calibrated and setup with the display and keys, with setup parameters stored in non-volatile internal memory. In operation, controllers continously measure and take control action, displaying measurements and control states on the front panel display. These controllers have a set of digital inputs and outputs which may be attached to PLC's or PC's with approriate interfacing circuitry for control or data reporting. Stand-alone controllers are mounted in DIN standard panel-mounted packages.

PC Peripherals and Stand-alone Controllers

PC/104 Compatible Controllers - For Integration with Compact Industrial Computers

754P-LC3 Single Channel Controller 4- or 6-wire bridge excitation Precise analog and A/D conversion circuitry 4 digital inputs and 4 digital outputs On-board eeprom configuration storage Simple setup and calibration utilities C function library for program development User's Guide is Available on-line (662KB pdf file).	754P-LC3 Single Channel PC/104 Compliant Loadcell Controller
754P-LC4 Four Channel PC/104 Compliant Loadcell Controller	754P-LC4 Four Channel Controller Four independent loadcell interfaces Single excitation, 2 - or 4 -wire brige input 4 digital inputs and 4 digital outputs Each channel separately calibrated and configured Simple setup and calibration utilities C function library for program development User's Guide is Available on-line (688KB pdf file).

ISA Compatible Controllers - For Desktop PC's in Laboratory or Distribution Applications

754P-ISA Single Channel Controller 4- or 6-wire bridge excitation Precise analog and A/D conversion circuitry 4 digital inputs and 4 digital outputs On-board eeprom configuration storage Simple setup and calibration utilities C function library for program development

Scanning Devices # 754P-ISA Loadcell Controller for Desktop PC

Panel Mounted Controllers - For Independent Measurement and Control

754D-LM* Single Channel Controller ( * ) Models for Fill-by-Weight, Weigh against Setpoints 4- or 6-wire bridge excitation accessed by screw terminal block 4 digital inputs and 4 digital outputs accessed by 9-pin dsub connector Six digit numeric display for measurment, two digit status display Front panel key-driven setup and calibration procedures On-board eeprom calibration and setpoint storage 1/8 DIN panel mounted packaging

Scanning Devices # 754D-LM3 1/8 DIN Panel Mounted Loadcell Controller

PRODUCT DESCRIPTION

Scanning Devices loadcell controllers deliver measurement and control functions which may be used in a wide variety of applications. They feature compact form and versatility in systems which require precise measurement of weight or force combined with processing and storage.

Precise analog circuitry provides accurate excitation and measurement of 350 ohm resistance Wheatstone bridge type transducers, such as strain gage load cells. Instruments have jumper-selectable input ranges of 2 mv/V and 3 mv/V. Custom input ranges for use with other rated output transducers may be requested on special order.

Popular control functions are built into the instrument include the logic sequence for fill-by-weight and/or setpoint comparisions.

Fill-by-weight is initated by a digital input, tares the loadcell, energizes a digital output to begin the fill, energizes a second output at a "slow-down" setpoint, and energizes a third to indicate completion.

Four setpoints may be entered, stored and associated with a digital output. Measurements are continously compared to setpoints and digital outputs set/cleared depending on the result of each comparison. The digital outputs indicate the relationship between measurements and setpoints.

PC/104 and ISA loadcell controllers may be directly accessed by DOS-based or Windows-based programs to perform an almost unlimited variety of tasks such as data acquisition, analysis, display and process control. A library of C functions and sample programs in C and Q-Basic simplify programming.

"Embedded Systems for Weight and Force Measurement Applications", an article discussing the PC/104 Loadcell Controllers was published in Circuit Cellar Ink, June 1996. View a text-based condensed version of this article. Email Scanning Devices Inc mail@scanningdevices.com to request a reprint of the article. Reprints include referenced figures, drawings and diagrams not found in the text-based version.

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SPECIFICATIONS
BUS INTERFACE
Bus	Conforms to PC/104 or ISA specifications
Power Requirements	+12 VDC, +5 VDC provided by PC, 24 VDC for panel mounted controllers
ANALOG AND CONVERSION CIRCUITRY
Excitation	4.3 - 5.0 VDC @ 150 mA, buffered
Sensor type	350 ohm resistive strain gage transducers
Gain	2 mV/V or 3 mV/V, jumper selectable
Measurement resolution	18-bit (1 part in 262,144)
DIGITAL INPUTS
Number	4
Type	Schmitt trigger with 10 kohm pull-up resistor to +5 V supply
Hysteresis	2.2 V typical
DIGITAL OUTPUTS
Number	4
Type.	Current sinking npn transistor switches with grounded emitter
Output Current	50 mA max
Collector-Emitter Voltage	30 V max while in non-conducting state
PHYSICAL
Dimensions	conforms to PC/104, ISA or DIN standards

Custom Logic, Signal Level or other variants are availabe on request. Contact Scanning Devices with your specific requirements.

111 Terrace Hall Avenue Burlington, Massachusetts (USA) 01803 1-781-272-5135 FAX: 1-781-272-4856 Email us: mail@scanningdevices.com

Scanning Devices Inc.

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