Using probe correction factors – NARDA 8718B User Manual

Page 25

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24

Operating the Meter

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.
Ultra-broadband probes contain both high frequency and low

frequency sensors. These probes require six checks – three

high frequency and three low frequency.

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).

A probe that does

not show a move-

ment of the bar

graph for all three

(or six) tests may be

damaged and should

not be used to make

measurements.

N

ote

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