ESCO Technologies ETS-Lindgren 7405 User manual

Model 7405
Near-Field Probe Set
User Manual

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ETS-Lindgren Inc. reserves the right to make changes to any product described
herein in order to improve function, design, or for any other reason. Nothing
contained herein shall constitute ETS-Lindgren Inc. assuming any liability
whatsoever arising out of the application or use of any product or circuit
described herein. ETS-Lindgren Inc. does not convey any license under its
patent rights or the rights of others.
© Copyright 1996–2022 by ETS-Lindgren Inc. All Rights Reserved. No part
of this document may be copied by any means without written permission
from ETS-Lindgren Inc.
Trademarks used in this document: The ETS-Lindgren logo is a trademark of
ETS-Lindgren Inc.
Revision Record | MANUAL,7405 PROBE SET | Part #399107, Rev. K
Revision Description Date
A–E
•Initial Release
•Updates / edits
February, 1996–January, 1999
F Updated Preamplifier
Gain chart; rebrand October, 2009
G
Updated
measurement and
characterization
information
May, 2013
H Added temperature
range July, 2016
J Removed references
to battery/charger January, 2019
K Warranty information
removed February, 2022

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Table of Contents
Notes, Cautions, and Warnings............................................... vi
Safety Information .................................................................... vi
1.0 Introduction .......................................................................... 7
Magnetic (H) Field Probes .......................................................................... 8
Electric (E) Field Probes ............................................................................. 8
Ball Probe ........................................................................................... 9
Stub Probe.......................................................................................... 9
Standard Configuration ............................................................................... 9
Optional Items (Sold Separately) .............................................................. 10
ETS-Lindgren Product Information Bulletin ............................................... 10
2.0 Maintenance ....................................................................... 11
Service Procedures .................................................................................. 11
3.0 Specifications..................................................................... 13
Model 7405............................................................................................... 13
Preamplifier .............................................................................................. 13
4.0 Operation ............................................................................ 15
Typical Configuration ................................................................................ 15
Probe Selection ........................................................................................ 16
Preamplifier Use ....................................................................................... 17
5.0 Typical Performance Factors ........................................... 19
Magnetic (H) Field Probes ........................................................................ 20
901 (6-cm Loop) ............................................................................... 20
902 (3-cm Loop) ............................................................................... 21
903 (1-cm Loop) ............................................................................... 22
Electric (E) Field Probes ........................................................................... 23
904 (Ball Probe)................................................................................ 23
905 (Stub Probe) .............................................................................. 24
Preamplifier Gain ...................................................................................... 25
0.01 MHz –3 GHz ............................................................................. 25
6.0 Common Diagnostic Techniques..................................... 27
Locating Radiating Sources ...................................................................... 27

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Signal Demodulation......................................................................... 29
Examples.......................................................................................... 30
Using Sniffer Probes ......................................................................... 32
Diagnosing Radiation Causes................................................................... 33
Common and Differential Mode Current Flow.................................... 35
Differential Mode Techniques............................................................ 40
Common Mode Techniques .............................................................. 42
Pre-Screening Alternate Solutions ............................................................ 43
Evaluating Alternate Solutions .......................................................... 46
Appendix A: EC Declaration of Conformity .......................... 49

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Notes, Cautions, and Warnings
Note: Denotes helpful information intended to provide tips for better
use of the product.
Caution: Denotes a hazard. Failure to follow instructions
could result in minor personal injury and/or property
damage. Included text gives proper procedures.
Warning: Denotes a hazard. Failure to follow instructions
could result in SEVERE personal injury and/or property
damage. Included text gives proper procedures.
Note: See the ETS-Lindgren Product Information Bulletin for safety,
regulatory, and other product marking information.
Safety Information
High Voltage: Indicates presence of hazardous voltage.
Unsafe practice could result in severe personal injury or
death.

www.ets-lindgren.com Introduction
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1.0 Introduction
The ETS-Lindgren Model 7405
Near-Field Probe Set includes three
magnetic (H) field and two electric (E)
field passive, near-field probes designed
for use in the resolution of emissions
problems.
The Model 7405 provides a
self-contained means of accurately
detecting H-field and E-field emissions,
and includes a 20 cm extension handle
to provide access to remote areas in
larger units. Made of injection molded
industrial grade plastic, the probes are
durable, light weight, and compact.
The probes provide a fast and easy means of detecting and identifying signal
sources that could prevent a product from meeting federal regulatory
requirements. This set is a convenient and inexpensive tool for extending the
capability of a spectrum analyzer, oscilloscope, or signal generator.
A near-field probe is an essential tool for quick and efficient EMC/EMI
engineering. Using near-field probes and an oscilloscope can produce the
following results:
•Gain information about the source and location of the radiation
member.
•Reduce test expense by adding inexpensive equipment for solving
EMC/EMI problems.
The Model 7405 is used for diagnostics purposes, and does not
require calibration.

8Introduction
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Magnetic (H) Field Probes
The Model 7405 includes three
H-field probes of varying size and
sensitivity: models 901, 902,
and 903. These probes are highly
selective of the H-field while being
relatively immune to the E-field.
Each H-field probe contains a
single turn, shorted loop inside a
balanced E-field shield. The loops
are constructed by taking a single
piece of 50 ohm, semi-rigid coax
from the connector and turning it
into a loop. When the end of the
coax meets the shaft of the probe,
both the center conductor and the
shield are 360 degrees soldered to
the shield at the shaft.
Then a notch is cut at the high point of the loop. This notch creates a balanced
E-field shield of the coax shield. The loops reject E-field signals due to the
balanced shield.
Electric (E) Field Probes
The Model 7405 includes two E-field probes: the stub probe (model 904) and the
ball probe (model 905). Due to the small sensing element, the stub probe is
relatively insensitive. This is an advantage when the precise location of a
radiating source must be determined. For example, while moving the stub probe
over the pins of an IC chip, variations can be noted at spaces as close as two or
three pins.
By comparison, the ball probe is much more sensitive. The larger sensing
element does not offer the highly-refined definition of the source location which
the stub probe allows, but it is capable of tracing much weaker signals. The
impedance of the stub probe is essentially the same as that of a non-terminated
length of 50 ohm coaxial cable.

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BALL PROBE
The shaft of the model 904
ball probe is constructed of a
length of 50 ohm coax. The coax is
terminated with a 50 ohm resistor
in order to present a conjugate
termination to the 50 ohm line. The
center conductor is extended
beyond the 50 ohm termination
and attached to a 3.6-cm diameter
metal ball, which serves as an
E-field pick up. The absence of a
closed loop prevents current flow,
allowing the ball probe to reject the
H-field.
STUB PROBE
The model 905 stub probe is made of a
single piece of 50 ohm, semi-rigid coaxial
cable with 6 mm of the center conductor
exposed at the tip. This short length of
center conductor serves as a monopole
antenna to pick up E-field emanations.
With no loop structure to carry current, the
stub probe rejects the H-field.
Standard Configuration
•H-field probes (3)
•E-field probes (2)
•20 cm extension handle
•Carrying case

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Optional Items (Sold Separately)
•Preamplifier, including wall-mounted power supply (115 VAC or
230 VAC available)
ETS-Lindgren Product Information Bulletin
See the ETS-Lindgren Product Information Bulletin included with your shipment
for the following:
•Warranty information
•Safety, regulatory, and other product marking information
•Steps to receive your shipment
•Steps to return a component for service
•ETS-Lindgren calibration service
•ETS-Lindgren contact information

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2.0 Maintenance
Before performing any maintenance,
follow the safety information in the
ETS-Lindgren Product Information
Bulletin included with your shipment.
Maintenance of the Model 7405 is limited
to external components such as cables
or connectors.
If you have any questions concerning
maintenance, contact ETS-Lindgren
Customer Service.
Service Procedures
For the steps to return a system or system component to ETS-Lindgren for
service, see the Product Information Bulletin included with your shipment.
WARRANTY

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www.ets-lindgren.com Specifications
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3.0 Specifications
Model 7405
Primary
Sensor Type
E/H or H/E
Rejection
Upper
Resonant
Frequency
901
6-cm loop H-Field 41 dB 790 MHz
902
3-cm loop H-Field 29 dB 1.5 GHz
903
1-cm loop H-Field 11 dB 2.3 GHz
904
3.6-cm ball E-Field 30 dB >1 GHz
905
6-mm stub tip E-Field 30 dB >3 GHz
Preamplifier
Absolute Maximum Ratings: •Input Voltage (DC): 12 VDC
•Input Voltage (AC): +20 dBm
Bandwidth: 100 kHz–3 GHz
Noise Figure
(Ref. 50 ohms):
3.5 dB (typical)
Saturated Output Power
(at F = 100 MHz):
+12.0 dBm
1 dB Gain Compression
(at F = 100 MHz):
+10.0 dBm
Third Order Intermodulation
Intercept:
+23 dBm

14 Specifications
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Environmental
Storage and Operating
Temperature:
0°C to 45°C
32°F to 113°F

www.ets-lindgren.com Operation
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4.0 Operation
Before connecting any components, follow the
safety information in the ETS-Lindgren
Product Information Bulletin included with your
shipment.
Typical Configuration
1. Choose the appropriate probe from the Model 7405 Near-Field
Probe Set. See Probe Selection on page 16.
2. Connect a coaxial cable from the probe to the signal analyzing device;
typically, an oscilloscope or spectrum analyzer.
If needed, place the extension handle between the probe and the
coaxial cable.
3. Adjust the signal analyzing device as required.

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Probe Selection
Choosing the correct probe is determined by the following:
•Whether the signal is E or H:If the signal is primarily is E-field, use
the ball probe or stub probe. If the signal is primarily H-field, use one of
the loop probes. If unknown, try one of each and select the one that
best picks up the signal.
•The strength of the signal: Select a probe that adequately receives
the desired signal of interest. Respectively, the ball probe and the
6-cm loop are the most sensitive of the E-field and H-field probes. The
stub probe and the 1-cm loop are the least sensitive.
•The frequency of the signal: If the signal is above 790 MHz, the
probe may go into resonance. See the upper resonant frequency listed
for each probe in Specifications on page 13.
In this illustration a
ball probe is used to
examine a flat cable.
The distributed
inductance over the
length of the cables
makes them
particularly susceptible
to common mode
problems. High
impedance sources
such as this are best
examined with an
E-field probe.
•The physical size of the space where the probe must fit:
Model 7405 includes a variety of sizes. See pages 8–9 for a
description of each probe.

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•How closely you want to define the location of the source: Choose
the probe that gets as close to the signal source as required. Select a
large probe and begin outside a unit, then move closer to the source
and switch to smaller probes to identify the location of the source.
For example, the smallest probes should allow you to determine
exactly which circuit on a printed circuit board is radiating. This kind of
refinement provides the ability to stop the radiation at the source rather
than shielding an entire unit.
Preamplifier Use
The optional preamplifier increases the sensitivity of your test system. The
preamplifier is connected to the input of the signal analyzing device, and the
coaxial cable from the probe is connected to the preamplifier. A switch on the
preamplifier activates power to the unit; when power is activated, a panel light
illuminates.
The preamplifier is powered by a wall-mounted DC power supply. Both 115 VAC
and 230 VAC models are available. The preamplifier includes a standard
DC power connector.

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www.ets-lindgren.com Typical Performance Factors
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5.0 Typical Performance Factors
The following graphs represent typical measurement. Individual probe
results may vary.
Probe performance factor is defined as the ratio of the field presented to the
probe to the voltage developed by the probe at the BNC connector, PF = EN. By
adding the performance factor to the voltage measured from the probe, the field
amplitude may be obtained.
All probes in the Model 7405 Near-Field Probe Set were characterized in a
transverse electromagnetic mode (TEM) cell which presented a 377 ohm field.
The H-field probes only respond to the H-field; however, the equivalent E-field
response is graphed. This may be done if the field is assumed to be a
plane wave with an impedance of 377 ohms. The reason for graphing the factors
this way is to allow estimation of the strength of the far-field. If H-field amplitude
is desired, subtract 51.52 dB from the performance factor as indicated on the
graph.

20 Typical Performance Factors
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Magnetic (H) Field Probes
901 (6-CM LOOP)