Condimmu and Radimmu

These programs were a first-generation suite of programs for running conducted and radiated immunity.  They are written in Turbo-C and run under Dos.

First was the Condimmu program for running conducted immunity tests to IEC 1000-4-6.  It started out as a quick-and-dirty program to get the lab up and running.  They did not have any software at the time that would work with the instrumentation they had on hand. It started out as a simple program to collect signal generator levels during a calibration and replay them for a test.  Gradually it grew in functionality. It also became the basis for the Radimmu program.

The Radimmu program grew out of the need for running radiated immunity tests to IEC 1000-4-3 and Bellcore GR-1089 tests. The software available either did not have some features that were needed, or did not work with the available instrumentation. As new test methods and requirements arose, the software was changed/enhanced. There were versions written for 1000-4-3 uniform field method, SAE/Ford Triplate, TEM-cell, and SAE net-power free-field methods.

Conducted immunity tests are performed by injecting radio frequency signals onto cables coming from the product being test. The injection method used depends on the test standard as well as the type of cable. Power lines, for instance, will usually have the signal injected by a CDN (Coupler/Decoupler Network). The product is monitored during the test to insure it continues to operate properly.

Radiated Immunity tests are performed by pointing an antenna at the product and radiating it with radio-frequency energy. The type of antenna used depends on the frequency range being tests.  Generally speaking, a hybrid broadband bilog antenna is used for IEC 1000-4-3 tests, from 26 to 1000 MHz. For tests requiring higher field strengths, separate biconical and log-periodic antennas may be used. Above 1000 MHz, a horn antenna is generally used. For frequencies below 26 MHz, a parallel-rod e-field generator is used.

The reason for having separate conducted and radiated immunity tests has to do with the nature of radio frequency signals. Low frequency signals have longer wavelengths and can be much longer than the longest dimension of a product. The product itself may be insignificant relative to the wavelength of the low frequency signal. However, cables coming from the product can act as antennas and conduct the signal into the product, particularly the powerline. High frequency signals, on the other hand, can excite the product cabinet itself, or even leak in through openings in the product. Generally speaking, radiated immunity tests are not performed below 26 MHz, and conducted immunity tests are not done above 230 MHz. There are exceptions to this based on the type of product and the test standards that apply to it.

The Condimmu program was phased out of service.  It was replaced by the RadCon program.