3 Probe Selection

 

Introduction

 

The 8700 series RF measurement system offers a very broad

 

selection of probes. The factors that you should consider in

 

selecting the probe, or probes, best suited for your task are

 

described in this section.

 

Key Factors in Selecting a Probe

FREQUENCY

The probe frequency range should include the frequencies of all

RANGE

the emitters to be surveyed at one time.

POWER

The measurement range of the probe should be adequate for

DENSITY

the field levels that you anticipate, i.e., do you expect strong

OR FIELD

fields or weak fields? Probes give more accurate and more

STRENGTH

stable readings when they are not used at the extreme low end

 

of their sensitivity range. Therefore, if you anticipate measuring

 

very weak fields, select a probe with a lower power full-scale

 

measurement range to get greater sensitivity. In contrast, higher

 

power probes give additional safety margins, especially at

 

microwave frequencies where field strength can change rapidly

 

with a small change in distance to the source. Select a probe

 

with a higher power full-scale measurement range if you

 

anticipate measuring high level fields.

ELECTRIC FIELD VERSUS MAGNETIC FIELD

Most standards recommend that you measure both electric (E) and magnetic (H) fields below 300 MHz (due to the possibility that measurements may be made in the near field). Since most experts agree that the electric field poses a greater danger at lower frequencies due to induced and contact currents that can occur, the electric field is normally measured first. Higher frequency measurements are normally made of only the electric field since measurements will generally be made in the far field.

Chapter 3 Probe Selection

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