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Does my Comb Generator Require Calibration?
This brief technical note from Com-Power Corporation addresses the common question of whether comb generators used in EMC labs need to be formally calibrated. The answer is grounded in how the device is actually used. Since the comb generator's primary role is as a reference source for periodic site verification checks rather than as a precision measurement instrument, there is no external standard against which it can be formally calibrated and no defined pass/fail criteria for its output. Any third-party calibration of a comb generator would amount to nothing more than a characterization of its output levels at a point in time and at a different test site, which would hold limited relevance because the test environment itself influences the measured values. The document explains the correct process: initial reference measurements are taken when the measurement system is already confirmed to be in good order, ideally immediately after all individual components have been calibrated and site attenuation verified. These become the baseline. Before each subsequent test, the same measurements are repeated and compared to the baseline within a tolerance of typically ±3 dB. This reference measurement process is itself considered the effective calibration of the comb generator. ISO 17025 accredited laboratories are also noted to be permitted to calibrate their own equipment, making external calibration of a comb generator unnecessary in that context as well.