NVSI Uses NI LabVIEW Real-Time and FieldPoint to Update 50 Ton Load Cell Testing System - Customer Solutions - National Instruments

http://sine.ni.com/csol/cds/item/vw/p/id/583/nid/124400 (1 of 3)22/03/2006 23:41:11

view cart | help | search

View by Language

You are here: NI Home > Solutions > Customer Solutions > View by Language

Customer Solutions

NVSI Uses NI LabVIEW Real-Time and

FieldPoint to Update 50 Ton Load Cell

Testing System

Author(s): Jason Reid, Neo Vista System Integrators Pty Ltd: Christopher Relf,

Neo Vista System Integrators Pty Ltd; Liam Granger, Neo Vista System

Integrators Pty Ltd; Laurent Raynal, Neo Vista System Integrators Pty

Ltd

Industry: Industrial Controls/Devices/Systems

Product: FieldPoint, LabVIEW, LabVIEW Real-Time, Programmable Automation

Controllers (PACs)

The Challenge: Replacing an antiquated load cell testing system with a networked,

database-driven, automated system with higher accuracy, expanded

capability, and lower test times.

The Solution: Using a National Instruments LabVIEW Real-Time and NI FieldPoint

programmable automation controller (PAC) to control the system and

achieve highly accurate force application and measurement, while controlling the UUT steady-state temperature and humidity set points.

Improving Load Cell and Environmental Control Parameters

The National Standards Commission (NSC) performs pattern approval type testing on

measuring instruments used for trade

purposes in Australia. Part of this process involves the use of a 50 ton load cell, with two

temperature-controlled chambers used to test

and calibrate third-party load cells. An international recommendation (OIML R60 -

from the International Organization of Legal

Metrology) prescribes the principal metrological static characteristics and static

evaluation procedures to follow.

The NSC requested a general improvement

to the load cell and environmental control

parameters, with database control and comprehensive data logging features, which

50 Ton Load Cell

Tester

Customer Solutions

View by Application Area

View by Industry

View by Product

NVSI Uses NI LabVIEW Real-Time and FieldPoint to Update 50 Ton Load Cell Testing System - Customer Solutions - National Instruments

http://sine.ni.com/csol/cds/item/vw/p/id/583/nid/124400 (2 of 3)22/03/2006 23:41:11

proved impossible with off-the-shelf solutions that were currently available. The load cell consists of an inner stack containing ten 500 kg

weights and an outer stack containing ten 150 kg weights. Test loads of

50 tons are possible as a result of the balance arm, which amplifies the load using a 10:1 ratio when test objects are placed inside the large

test chamber.

We developed the solution using two LabVIEW Real-Time executables

residing in two separate FieldPoint controllers (one controls the temperature environment of the chambers and the other controls the

motors used to apply the load). We used the LabVIEW Real-Time PID

algorithms running in both FieldPoint systems. The NI LabVIEW Database Connectivity Toolkit provided us with the ability to

communicate to the NSC SQL server, which stored test profiles and

recorded test results.

We used the following FieldPoint modules:

● Quadrature Encoder Input Module (QUAD-510)

● RTD Input Module (RTD-124)

● Analog Input Module (AI-100) ● Analog Input Module (AI-110)

● Digital Input Module (DI-330)

● Voltage Output Module (AO-210)

● Relay Module (RLY-420)

● Pulse Output Module (PG-522)

Two Allen Bradley motors control the loading and unloading of the

weights on the inner and outer stacks, and we used the quadrature

encoder module to determine the position of the stacks. Setpoints stored in the SQL database indicate the position required for the

addition of each of the weights.

A further motor lowers and raises the balance arm to ensure that it is

horizontal at all times. A Schick laser displacement sensor provides the input parameter passed to an embedded LabVIEW PID application

running on the FieldPoint controller, which controls the motor speed

profile as the balance arm is adjusted. A test typically consists of exercises (the maximum load of the test is loaded during a short time,

as defined by the OIML R60 recommendation), steps (the maximum

load of the test is gradually applied in a series of steps, a profile of which is contained in the SQL database) and/or creeps (the maximum

load of the test is loaded during 30 minutes). A standard test can last

anywhere between a few hours and several days, containing numerous cycles, and operating without user intervention, which requires the

ruggedness and reliability of the FieldPoint controllers running a real-

time operating system.

We used two NI Compact FieldPoint systems (one for load application

and another for environmental monitoring and control) and a PC for full- system control and load monitoring. We linked these systems using the

LAN. We also uploaded test sequences and part identifiers from a

network SQL database.

UUT Environmental Control

The system records temperature, load, and pressure then stores it in the SQL database during the test, at intervals defined by the test

profile. Reusing code that had been developed on the NSC

environmental chamber monitoring system, we attain temperature setpoints to an accuracy of ±0.1°C. This code is modular and easily

extendable to incorporate the monitoring and control of other physical

NVSI Uses NI LabVIEW Real-Time and FieldPoint to Update 50 Ton Load Cell Testing System - Customer Solutions - National Instruments

http://sine.ni.com/csol/cds/item/vw/p/id/583/nid/124400 (3 of 3)22/03/2006 23:41:11

phenomena, including humidity.

We execute a test at different temperatures controlled by the environmental portion of the software. A typical test may require the

load tests to be applied when stability has been achieved at +20°C,

+40°C, -10°C, +10°C, and again at +20°C.

Overall System Improvements

The system is easily configurable using a database front end and can

be quickly altered using the LabVIEW Real-Time development system and FieldPoint hardware. The system can perform user-customizable

tests on load cells up to 50 tons, with strict environmental control and

monitoring of the load cell itself, satisfying regulatory recommendations and constraints.

We developed the environmental control systems used in this solution

using an existing NVSI user solution, currently used by the NSC. Using

the existing modular code and documentation, we delivered the overall solution at a significant time and fiscal saving, as opposed to creating

the solution from scratch.

Similarly, we are currently porting the code produced for this system to

a smaller 500 kg Load cell Test Rig at the NSC site in North Ryde, with

only minor adjustments to suit differing hardware. The technique of modular code reuse also significantly decreases the incidence of call

outs, simplifies user training, and documentation.

For further information, contact:

Christopher Relf

National Manager - Australia

Neo Vista System Integrators Pty Ltd

Tel: +61 2 9809 7899

Fax: +61 2 9809 7499

E-mail: christopher@nvsi.com.au

Web: www.nvsi.com.au

My Profile | Privacy | Legal | Contact NI © 2006 National Instruments Corporation. All rights reserved.