Atec 8700, 8741d, 8754D, 8760D, 8761D User Manual

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Electric and Magnetic Field Measurement

8700 SERIES PROBES

PROBE SELECTION

The 8700 series system has the most extensive selection of probes available from any source in the world. The
factors that you should consider in selecting the probe, or probes, best suited for your task are:

Frequency Range

Power Density or

Field Strength

Electric Field versus

Magnetic Field

Flat Response or

Shaped Frequency Response

The probe frequency range should include the frequencies of all the emitters
to be surveyed at one time.

The measurement range of the probe should be adequate for the field levels
that you anticipate, i.e., Do you expect strong fields or weak fields? Probes
give more accurate and more stable readings when they are not used at the
extreme low end of their sensitivity range. Therefore, if you anticipate meas
uring very weak fields, select a probe with a lower power full-scale measure
ment 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.

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 dangerat lower frequencies due to inducedand contact
currents that can occur, the electric field is normally measured first. Higher
frequency measurements are normally made only of the electric field since
measurements will invariably be made in the far field.

Flat response probes are the most common. Narda’s patented shaped
frequency response probes read out in Percent of Standard and are par
ticularly useful in complex, multi-signal environments where exposure
limits are different for the various emitter frequencies and in classified
environments.

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Size and Minimum

Measurement Distance

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The majority of the 8700D series probes have four inch (10 cm) diameter
heads. The minimum measurement distance for these probes is about 4 in
(10 cm) from the outside surface of the probe. Measurements made at
closer distances can result in inaccurate readings due to capacitive cou
pling. The Models8721D, 8723D, 8725D and 8783D havetwo-inch (5 cm) di
ameter heads that can be used as close as 2 in (5 cm) from the source to the
outside of the probe. These probes are ideal for the measurement of
waveguide leaks. Similarly, the Model 8781D has a one-inch (2.5 cm) di
ameter head with a flexible shaft that isdesigned for locating leaks in densely
packaged microwave systems. The 8783D also has a flexible shaft.

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ENVIRONMENTAL SPECIFICATIONS

Temperature

Operating -10°C to +55°C
Non-Operating -40°C to +75°C

Humidity 0% to 95%, non-condensing

OUTLINE DRAWINGS

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4

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RF Radiation

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Meters/Monitors

2

SHAPED FREQUENCY RESPONSE PROBES

The goal in designing and manufacturing a traditional,
“flat” frequency response probe is to make the probe
equally responsive to energy at every frequency within its
rated frequency range. In contrast, Narda’s patented
shaped frequency response probes are designed and
manufactured so that their sensitivity mirrors a particular
standard as closely as possible. For example, many of
the major standards in the world set limits for maximum
exposure at the lowest frequencies to 100 mW/cm
These same standards typically limit exposure in the VHF
region to 1 mW/cm
wave region. A shaped frequency response probe de
signed for such a standard is 100 times more sensitive in
the VHF region than at the lowest frequencies. The result
is that energy from all sources within the probe’s rated fre
quency range are not only summed in terms of RMS

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and to 5-10 mW/cm2in the micro

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power but are also weighted in direct proportion to a par­ticular standard.

The readout on the meter is shown in terms of Percent of
Standard. The full scale of Narda’s shaped probes is typi­cally either 300% or600% of a standard. This permits mea­surements of exposure environments where the weighted
field strengths range from as high as three to six times the
maximum permissible exposure1 (MPE) level to environ
ments where the levels are less than one percent of the
MPE. For a more complete description of how shaped
probes are used in complex, multi-signal environments,
refer to the application note Measuring RF Levels at
Multi-Signal Sites that begins on page 609.

1

Maximum Persmissible Exposure (MPE) level is only one of several
terms used to designate the limits imposed by various standards.
Other common terms are: Threshold Limit Value (TLV), Permissible
Exposure Level (PEL), action limit, and reference level.

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SELECTING A SHAPED PROBE

1. Determine the standard that you will be using.

2. Determine which tier of the standard will be
used, i.e., Occupational Environment or
General Population Environment.

3. Determine whether you must measure the
magnetic field as well as the electric field.

4. Select a probe model from the table on the
next page.

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MAJOR INTERNATIONAL STANDARDS AND GUIDANCES

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SHAPED PROBE SELECTION GUIDE

STANDARD OR GUIDANCE TIER MODEL

FCC 1997

Japan RCR-38

FCC 1997 General Population B8742D 300 kHz - 3 GHz 600% of Std E

IEEE C95.1-1991

NATO STANAG 2345

ACGIH

Canada Safety Code 6 RF Workers C8722D 300 kHz - 50 GHz 300% of Std E

ICNIRP 1998 Occupational D8722D 300 kHz - 50 GHz 300% of Std E

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Occupational / Controlled

Controlled

Controlled

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A8722D 300 kHz - 50 GHz 300% of Std E

A8742D 300 kHz - 3 GHz 600% of Std E

B8722D 300 kHz - 50 GHz 300% of Std E

A8732D 300 kHz - 200 MHz 300% of Std H

FREQUENCY

RANGE

FULL SCALE

RANGE

FIELD

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