You’ve lost many hours running EMC tests. EMC specifications keep changing, and the product development schedule is slipping. This could be the time to automate your EMC testing through software.
To meet today’s EMC testing needs, your software must have the power to run all the required tests and the flexibility to make changes on-the-fly. In software terms, this means that you must have many instrument driver libraries, specification libraries, test setup libraries, and function libraries. You also must have the power to add libraries, delete them, create them, edit them, and interface them easily.
Today’s easy-to-use software packages lead to better, faster, more repeatable results and better documentation. Dramatic advances in the modular, flexible, graphical programming process found in today’s EMC test software packages make them serious contenders for integrating a test system.
General Requirements
Make sure your computer and software are compatible. A common platform is a PC running on Windows, but you may have other preferences.
For all of your EMC emissions and immunity tests, the software should support all the specifications that apply to your product.
Get the appropriate bus interface and software drivers for each piece of test gear. Find out which drivers are built in and which ones you must add. Dedicated software is easier to use, but may limit your choice of equipment. There should be automatic calibration and correction features for equipment, transducers, and cables.
Data must be analyzed for evaluation purposes and generation of tables, charts, and graphs, but all of it is not needed in the final report. See if a data-reduction feature is available.
The software should allow you to prepare the documentation needed to apply for product certification. Investigate whether it is worth the added expense of a separate reporting package.
To be easily reconfigurable for new requirements, you should be able to add or modify test libraries, specification libraries, device drivers, and test sequences without hard code changes. Look for easy-to-edit test parameters such as frequency ranges or limit curves and easy-to-patch test setups with manual override capabilities built in. Find out if software upgrades are readily available for modest fees and if there is a bulletin-board service.
Whether it is the capability to rotate a turntable, track a drifting frequency source, automate a sequence of batch tests, monitor a network, or correct ambient noise, the software must provide it.
Start at the Beginning
Find out which specifications apply to your product, and determine which tests are required. Investigate what test equipment will be necessary to run the tests. Make sure that all equipment has a similar test-port connector so you can operate them over a common bus, such as IEEE 488.
An EMC test system is configured by matching hardware and software components.
The software must have an instrument driver for each piece of test equipment and a library for each test.
Narrow the Selection
In considering an EMC test software package, answer the following questions:
Of the four types of tests—radiated emission, conducted emission, radiated immunity, and conducted immunity, which are included?
What domestic, international, commercial, and military specifications are there complete tests for?
What software is available at the full compliance, precompliance, and product evaluation levels?
What operating systems does the software run on, and what are the computer requirements? What plug-in boards and driver software are needed?
What connection or bus will the computer need to run the test equipment?
Are there instrument drivers for all the test equipment you will run?
Are there libraries for all the tests you will run?
Is operator intervention required to run these tests, or are they completely automatic? Is manual override allowed?
How are the packages configured, and what are the prices?
What is the installed base of the software?
Look for Flexibility
EMC standards keep changing. To accommodate test revisions, you should be able to reconfigure the system easily. Also, you need to know:
Is the programming strictly graphical or iconic? How does it work?
Which programming languages will the software accept?
How may functionality be added or changed? Are hard code changes required?
How may tests be added, deleted, changed, or customized?
Does the software run anybody’s test equipment, or is it brand sensitive?
Which platforms will the software run on?
Is there third-party support for the software?
How often is the software upgraded, and how is it made available?
What report-generation features does the software have?
Are there prescan and data reduction features?
What difficult test situations does the software address?
What’s Out There?
Now that you have a pretty good idea what requirements you need in an EMC test software package, let’s take a look at what’s available. A number of companies, including Tektronix, Hewlett-Packard, Quantum Change/EMC Systems, and Electro-Metrics, offer software that addresses most test requirements.
For example, Tektronix markets the modular, Windows-based ES-K1 Software for conducted and radiated emissions testing. It contains a library of limit lines and routines required for commercial and military testing, according to Cliff Morgan, product marketing manager. Typically, it supports commercial and military standards such as EN55011 through EN55022 and MIL-STD-461/462. A limit-line editor allows new limit lines to be created and updated easily. Measurement routines called scripts also may be created or edited.
Mr. Morgan related one special problem tackled by the Tektronix’ software. It involved testing a product with maximum emissions that drifted from 179 MHz to 182 MHz. The software looked for the highest signal in a specified window centered around the original frequency and tested at the new maximum.
The capability to change limits also is supported by HP’s EMC test software, noted Dennis Handlon, product manager. It allows you to edit current regulatory limits and change or set up new transducer correction factors. You also can use the GUI to configure test sequences and customize test-equipment setups. To perform accurate compliance measurements, the signal from the equipment under test (EUT) should be maximized. The software accomplishes this by rotating the EUT, adjusting the antenna height, and identifying the maximum signal.
If test customization is what you really need, then TILE/ICS software from Quantum Change/EMC Systems may be the answer. You can customize the test to your requirements without any need to touch the code, noted Mike Hart, division manager. The software is modular so new features and upgrades can be done at any time. In most cases, adding the dynamically linked library (DLL) to the directory adds the new feature to the software.
In one instance, according to Mr. Hart, a customer who was contracting outside EMC testing was able to save time by using TILE software. Because of scheduling problems at local labs, the customer was forced to commit blocks of testing time four to six weeks before they actually were needed. In addition, it was taking two to three days to troubleshoot their products while on-site. “By using our software and a GTEM, the customer’s testing was compressed to a 15-minute cycle, with no lead time,” said Mr. Hart. “This allowed them to accelerate their development cycle.”
Avoiding hard code changes is a feature of Electro-Metrics’ EM3320 test software, said Tony Casale, software engineer at the company. The test configuration files are ASCII and can be altered with any text editor. Both emissions and immunity tests are conducted to give maximum flexibility.
Usually, the test packages support the full array of specifications in use. Many parameters can be changed in the course of a test and manually overridden. You can easily incorporate new requirements by creating a new test library with provided routines, change frequency and limit curves, and tailor the test by setting up parameters in hardware devices.
EMC Test Software
Software Helps Automate
Radiated, Conducted Tests
The SW1003 Software for radiated and conducted immunity testing helps meet the IEC 1000-4-3 and 1000-4-6 requirements. It features automated calibration, testing, and report generation. Thresholding and closed-loop leveling for precompliance-equipment checks are offered. Test parameters are user selectable and include a manual or an automatic probe, an antenna, and EUT turntable positioning for radiated immunity testing. Automatic data acquisition is provided for eight digital and 16 analog channels. Amplifier Research, (800) 933-8181.
Test Software Measures
Uncertainty Values
AEsoft Uncertainty Software provides three tools for determining and applying uncertainty to measurements: the uncertainty calculation tool, the application tool, and the statistics tool. Components of uncertainty may include errors caused by antenna factors, receiver calibration, cable losses, and test-site calibration. The uncertainty calculation tool shows the contribution of each element to the overall uncertainty and describes the uncertainty characteristics, including frequency dependencies. The application tool imports measurement data and applies the calculated uncertainty for viewing in tables and graphs. The statistics tool supplies the calculations to determine the uncertainty for an element. Atkinson Engineering, (540) 347-5716.
Software Is Configurable for
Radiated, Conducted Tests
The CIS9942 PC-Based Software is used to configure immunity tests including bulk current and voltage injection for conducted measurements and radiated testing in chambers or TEM cells. It also offers automatic and manual failure analysis. An edit function helps create or change instrument drivers. Drivers for IEEE 488-based signal generators, power meters, field sensors, spectrum analyzers, and voltmeters are included. Data for radiated field strength, signal-generator output, RF power output, and monitoring instrumentation is displayed during field calibration and when taking measurements. Schaffner-Chase, (973) 252-8001.
Radiated Immunity Software
Works GTEM Systems
GSOFT™ Software performs radiated immunity measurements in a gigahertz transverse electromagnetic cell (GTEM) and is designed for testing to SAE, ISO, and IEC regulations. It runs under the Microsoft Windows environment and controls the test process via the IEEE 488 bus. Up to 100 grid points for the field measurement plane, tests for data collection and uniformity verification, and an interactive mode for failure analysis are supported. EMC Automation, (512) 258-9478.
Software Controls Instruments
And Supports Data Analysis
TILE/ICS is an integrated information system that controls immunity and emissions test instruments, supports data analysis, and provides test reports. An instrument control subsystem helps create standard and customized test profiles. A test can be configured to include prompts, comments, and unit-under-test information. TILE/ICS can be integrated with a variety of data-base programs. Also included in TILE/ICS is a report-writing system that works with most word processors and supports macro creation for customized formats. Quantum Change/EMC Systems, (703) 207-0344.
Single Interface Accesses
Immunity Test Libraries
Powerstar EMC is a Windows-based software package with a single interface to control and operate instruments for testing to all IEC 1000-3-x, IEC 1000-4-x, and automotive immunity requirements. Test libraries are accessible via the main user interface. Each library contains the interfaces and links for the required hardware. Test functions include enable, disable, abort-on-fail, ignore fail, graphing, printing, and branching. Systems can be configured to include RS-232, IEEE, and VXI instrumentation. Schaffner EMC, (973) 379-7778.
Software Measures Radiated
EMI Emissions to 2 GHz
The HP 85876B Commercial Radiated EMI Measurement Software controls test equipment and the measurement process. It performs EMI emissions tests from 30 MHz to 2 GHz for commercial, industrial, scientific, and medical applications. The software is compatible with Windows 3.1, 95, and NT 4.0. Data and graphics can be exchanged between spreadsheets and word processors with no additional scripting and programming. Test configurations and libraries for global EMC test regulations are included. Hewlett-Packard, (800) 452-4844.
Software Measures Emissions
To EMC Standards
ES-K1 is modular, Windows 3.1-based software used for conducted and radiated emissions tests. IEEE 488 interface drivers are available for receivers, spectrum analyzers, and accessories. Compliant with exacting measurements for commercial, military, and international standards, this software features flexibility based on scripts, data reduction, an integrated data base, displays, and report configurations. Tektronix, (800) 426-2200.
Software Automates Testing
To MIL-STD-461D
EM3320 is comprised of a suite of software products designed to fully automate MIL-STD-461D radiated and conducted immunity tests. Test packages supporting RS101, RS103, CS101, CS109, and CS114 now are available. All default frequency ranges, step sizes, and limit curves are provided. Automatic procedures are provided for calibration and impedance checks. Customized and spot frequency test capabilities facilitate troubleshooting. Automatic scanning and leveling are standard. Test data can be displayed or printed. Electro-Metrics, (518) 762-2600.
Copyright 1998 Nelson Publishing Inc.
September 1998