Note
A probe that does not show a movement of the bar graph for all three (or six) tests may be damaged and should not be used to make measurements.
get a deflection on the bar graph but the amount of deflection is not important. Repeat for the other two test points to insure that the probe is working correctly. The D series magnetic field probes have a single, conductive test point that is used to simultaneously test all three sensors.
A microwave window on the right side of the probe is used for testing high frequency probes. Hold the probe parallel to the right side of the meter and position the probe head against the test window so that one of three arrows on the probe is pointing towards the window. These arrows indicate the location of the three sensors inside the probe. A deflection of any magnitude on the bar graph is acceptable. Repeat for the other two sensors to insure that the probe is working correctly.
Using Probe Correction Factors
All probes have a certain amount of frequency sensitivity. Frequency sensitivity is the amount of deviation from the correct measured value that a probe yields at various frequencies. Obviously, the smaller the deviation, the better. But since a certain amount of frequency deviation is unavoidable, the more frequencies that you calibrate the probe at, the better. At each calibration frequency, you have a correction factor.
Multiplying the reading on the meter by a correction factor marked on the handle of a Narda 8700 Series probe compensates for the probe’s frequency sensitivity. The Model 8718B is unique because it can perform this task automatically.
Correction factors can be used:
•When there is only a single emitter being surveyed.
•When there are multiple emitters all operating at the same frequency (this is often the case with industrial equipment).
24 | Operating the Meter |