LANGER EMV-Technik ESA1 User manual

ESA1-User manual 1117 PZ.doc
User Manual
Development System - Disturbance Emission
ESA1
Measuring disturbances emitted by a module –
comparative measurements at the developer's workplace
Copyright (C) Dipl.- Ing. Gunter Langer
Nöthnitzer Hang 31
01728 Bannewitz
15.05.2002

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LANGER
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DE-01728 Bannewitz
[email protected]
www.langer-emv.com
ESA1
Contents: Page
1Measurement procedure 3
2Description of the components 4
2.1 GP 23 ground plate 4
2.2 Z23 shielding tent 5
2.3 HFW 21 RF current transformer 7
2.4 HFA 21 RF bypass 8
2.5 Near-field probes 9
2.6 PA 203 preamplifier 9
2.7 Measurement set-up 10
3Practical procedure 11
3.1 Measuring with ESA1 11
3.2 ChipScan-ESA software 11
3.3 Localization through global changes to the unit under test 13
3.4 Reason analysis with near field probes 14
3.5 Modification of the module 15
4Measurement set-up variants 16
4.1 Measurement of the common-mode component 16
4.1.1 Unit under test with one cable terminal 16
4.1.2 Unit under test with several cable terminals 17
4.1.3 Unit under test with indispensable cables 17
4.1.4 Example: Measurements on a complex unit under test 18
4.1.5 External data lines 21
4.2 Measurement of the differential-mode component 22
5Safety instructions 23
6Warranty 24
7Technical parameters 25
7.1 Near-field probes 25
7.2 HFW 21 RF current transformer: 27
7.3 HFA 21 RF bypass 28
7.4 GP 23 ground plate 28
7.5 Z23-1 shielding tent 28
7.6 PA 203 preamplifier 28
8Scope of delivery 29
8.1 Content of the ESA1 case 31

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1 Measurement procedure
The ESA1 is suitable for carrying out comparative measurements of disturbances emitted by
modules directly at the developer's workplace. Since the effect of any changes to the module
becomes evident immediately, the time needed to optimize the unit under test can be dramatically
reduced.
Measuring with the ESA1 development system is based on the following considerations:
In most cases, it is not a component or conductor track of a unit under test that directly emits any
disturbances, rather the entire metal system of the unit under test is excited through electric or
magnetic coupling (i.e. in the near field). This metal system comprises the PCB itself and all
connected cables and metal parts such as housings, shielding plates etc. in its immediate vicinity.
The system in its entirety acts as an antenna and a source of emission. This excitation is roughly
equivalent to the disturbances emitted by the unit under test. To determine this excitation, measure
the exciting currents that flow, for instance, from a PCB to any cables connected.
The measurements are performed with a conductive ground plate to reduce any influences of the
measurement set-up, cable positions and local fields. Inject all exciting currents through short
capacitive coupling into the ground plate so that you have a small reproducible set-up (Figure 1).
Figure 1

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2 Description of the components
2.1 GP 23 ground plate
The GP 23 metal ground plate is the reference plane for the measurement set-up. It contains the
connectors to supplying the unit under test and preamplifier as well as the output of the latter.
(Figure 2).
Figure 2 GP 23 Ground Plate
The nickel-plated surface ensures a steady and reliable conductive connection to the HFW 21 RF
current transformer or HFA 21 RF bypass. Figure 3 shows the connections.
Figure 3 Connections/transits of GP 23 Ground Plate
The unit under test and the ground plate can be connected at any point via the HFA 21 RF bypass
or with copper foil adhesive tape, for instance.
- mains
- supply for PA 203
- shielded
- shielded
- earth connection
- shielded
°

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2.2 Z23-1 shielding tent
The shielding tent has been designed to shield the measurement set-up against external RF fields.
In case of problems in the VHF range or particularly high demands on the unit under test as in the
automobile industry, for instance, a conductive housing has to be used as a shield against ambient
disturbance fields. Shielding in the immediate vicinity of the unit under test is possible because all
cables to the unit under test are disconnected, coupled to the base plate through capacitive
coupling or filtered in a typical ESA1 measurement set-up.
The tent poles are folded upon delivery for ease of transport. Two rubber plugs snap into place in
the two rear openings of the ground plate to secure the tent against displacement (Figure 4).
Figure 4 ZG 23-1 tent poles folded (on GP 23 ground plate)
To put up the shielding tent, unfold the poles and insert them into the two rear openings of the
ground plate (Figure 5).
Figure 5 ZG 23-1 set up on the GP 23 ground plate

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Then pull the BZ23-1 shielding material over the poles from the back. Flexible magnetic strips are
attached to the edges of the shielding material. Press them against the edges of the ground plate
to ensure a conductive connection. Two magnetic strips are provided for the connector area: one is
fixed to the ground plate from the outside, the other one from the top. The front of the shielding
material can be opened and closed separately to ensure quick alternation between measuring and
modifying (Figure 6 to Figure 8).
After closing, press the lower edge of
the front and the lower edge of the left
and right side of the shielding material
against the ground plate.
An uninterrupted connection between
the ground plate and shielding
material is crucial for an effective
shielding.
Figure 6 Z23-1 shielding tent closed
If the tent is set up as shown in
Figure 7, you can see two press
buttons at the upper front edge of the
shielding material. Secure these
around the front transverse bar.
Figure 7 Z23-1 shielding tent open
You can tilt the whole tent backward
for ease of accessibility. The press
buttons stop the shielding material
from sliding down.
Figure 8 Z23-1 shielding tilted backwards
Attention! The shielding material is made from a thin, extremely conductive fabric. Protect the
shielding material against high mechanical stress from sharp-edged or pointed objects, for
example! Fold the shielding material in accordance with the folding instructions contained in the
bag!

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2.3 HFW 21 RF current transformer
The RF current transformer (Fehler! Verweisquelle konnte nicht gefunden werden. and
) measures high-frequency currents of up to 1 GHz on lines and diverts these currents to the base
plate.
Figure 9 HFW 21 RF Current Transformer
Figure 10 HFW 21 RF Current Transformer
(schematic)
The RF current transformer enables separate measurements of RF common-mode and differential-
mode currents. In practice, you can do this by connecting the RF current transformer into the
power supply circuit of the unit under test, for example. The supply voltage is connected to the
"POWER" socket connector of the current transformer via laboratory cable with a 4 mm plug and
the unit under test is connected to the "COM“ or "DIFF“ output via one of the supplied plugs. The
RF currents emitted by the unit under test are thus passed through the transformer, measured
(output above the 50 Ohm SMB socket) and diverted to the metal transformer ground plate through
capacitive coupling.
If the unit under test is connected via the "COM" output, the RF current transformer measures the
common-mode currents flowing on both lines whereas the differential-mode currents are measured
via the "DIFF" output.
The RF output voltage is independent of the direct current flowing through the transformer if
common-mode measurements are carried out. In case of differential-mode measurements, the RF
output voltage decreases according to the diagrams shown in section 7.
Please note:
A current surge occurs on switching on depending on how the unit under test is connected. If
the electrolytic capacitors, for example, are charged without limiting the current and the unit
under test is connected via the HFW 21 differential-mode output, there is a risk of damage to
the preamplifier or spectrum analyzer input!
Always connect the HFW 21 to the PA 203 or spectrum analyzer after the unit under test has
been switched on in such cases!
The same thing occurs during a short circuit in the unit under test if the electrolytic capacitors
of the external power supply unit are abruptly discharged. There is no risk if the HFW 21 is
operated via the common-mode output because these current pulses are compensated within
the transformer.
Current peaks also occur if the supply of the unit under test is connected to earth and thus to
the ground plate with an external power supply unit and the voltage in the unit under test is
short-circuited to the GP 23 ground plate during the measurement:

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2.4 HFA 21 RF bypass
The RF bypass (Figure 11) supplements the RF current transformer by providing another
capacitive or conductive connection from the unit under test to the ground plate if necessary.
Figure 11 HFA 21 RF Bypass
It is mainly used to simulate the data lines connected in normal operation and their capacitance
relative to the surroundings. Instead of the data line, a discrete capacitance is connected to the
signal output via a measuring line within the HFA 21 (Figure 12). Alternative it is possible to
connect each single signal step by step to the capacitance by a Probe tip (Figure 13). Defined RF
currents can thus be diverted to the ground plate. The HFA 21 contains capacitances from 10 pF to
100 nF.
Figure 12
Figure 13

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2.5 Near-field probes
Your ESA1 provides various near-field probes for measuring high-frequency magnetic and electric
fields depending on its version. The probes are connected to the preamplifier instead of the
HFW 21 and enable measurements in the area of the module, on tracks and components. The
goal is to find the RF field sources on the module in the unit under test and to detect and
understand the respective emission mechanisms. The developer can assess whether there are
any RF fields that interfere with neighboring modules, structural parts or shields and cause
disturbance emissions. In practical measurements the HFW 21 current transformer and the near-
field probes are mostly used alternatively.
A wide range of probes is provided for the various measuring tasks:
The near-field probes of the RF type are suitable for measurements of magnetic and electrical
fields in the frequency range between 30 MHz and 3 GHz. The probes differ with regard to the
probe head's size and design so that you can always select the optimal probe for the measuring
job. Please refer to the enclosed technical parameters (Section 7.1) for details about the precise
pattern of the field measured by the probe and typical examples for application.
Optionally available:
The near-field probes of the LF type are available for measurements in the frequency range
between 100 kHz and 50 MHz. They are particularly suitable in the areas of power supply,
converters, drives etc. The RF current paths of individual switching transistors and free-wheeling
diodes can be tracked and the respective magnetic fields measured, for example.
2.6 PA 203 preamplifier
The 20 dB preamplifier (Figure 14) operates in the frequency range between 100 kHz and 1 GHz
and is suitable for measurements with the RF current transformer and near-field probes. The input
and output are designed as 50 Ohm BNC plug-and-socket connectors and thus can be operated
with any spectrum analyzer or oscillograph.
Figure 14 PA 203 Preamplifier
The preamplifier is operated inside the shielding tent during measurements with the ESA1 system
(Figure 15). Filters are provided on the GP 23 ground plate for the preamplifier's output line and
power supply. The output signal reaches the spectrum analyzer via the enclosed double-shielded
BNC cable. Please use the enclosed plug-in power supply unit to supply power to the preamplifier.
Saturation effects will occur if the input level at the preamplifier exceeds 60 dBµV. In such a case,
the HFW 21 RF current transformer or the near-field probe should be directly connected to the
BNC socket connector on the ground plate without any preamplifier.

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2.7 Measurement set-up
Figure 15 Measurement set-up ESA1 (schematic)
First place the GP 23 ground plate with its socket connectors pointing to the left (under normal
conditions) and set up the shielding tent (description in section 2.2).
Inside the shielding tent plug the PA 203 preamplifier into the BNC socket on the ground plate.
Power is supplied via the enclosed plug-in power supply unit; outside the shielding tent plug the
power supply unit into the 3.5 mm connector (next to the BNC socket) on the outer left side of the
ground plate. Inside the shielding tent connect the 12 V input of the PA 203 to the 3.5 mm
connector on the ground plate via the enclosed power supply cable (approx. 10 cm long, two
power supply plugs). The "ON“ LED on the PA 203 must come on. Then connect the HFW 21 RF
current transformer or a near-field probe via the BNC-SMB connecting cable to the PA 203.
Connect the spectrum analyzer to the BNC socket on the outer left edge of the ground plate via the
enclosed BNC cable (double-shielded).
Please note:
There is a risk of destruction during HFW 21 operation when the differential-mode current is
measured and electrolytic capacitors are switched on or a short circuit occurs!
In such cases always connect the HFW 21 to the PA 203 or spectrum analyzer only after the
unit under test is switched on!

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3 Practical procedure
3.1 Measuring with ESA1
The measurements carried out with the ESA1 are relative measurements. Thus it is important to
define a measurement set-up and document the initial state first.
Measuring results from previous measurements under standard conditions provide crucial
information on critical frequency ranges and the extent of necessary improvements. First analyze
the measurement set-up required for these measurements:
-How have the PCBs been installed in the unit under test?
-Which connected cables are possible decoupling paths?
-How do these cables run inside and/or outside the unit under test? (e.g. cable harness in the
car in the immediate vicinity of a large metal surface)
-Which metal parts such as housing, shielding, stud bolts, water pipes etc. are in the immediate
vicinity (capacitive coupling)?
These considerations help determine modules and parts of modules as potential RF sources and
find the paths by which the high-frequency currents are possibly emitted. This information allows
you to design a measurement set-up so that the decisive emitted currents can be measured.
To confirm the measurement set-up, compare your measurement results with the results obtained
in far-field measurements. There will be deviations of course. However, it is crucial in this
comparison to find critical frequencies from far-field measurements with the chosen measurement
set-up and thus to prove the existence of the suspected sources and associated decoupling paths.
3.2 ChipScan-ESA software
ChipScan-ESA is a universal tool in the development of electronic modules which allows the
developer to manage the disturbance emission data measured with a spectrum analyzer.
The software enables:
a quick and easy configuration of spectrum analyzers
the logging of measured data for a quick comparison and for documentation
the linear/logarithmic plotting of measured data in 2D/3D diagrams
the storage of measured data for subsequent evaluation and comparison with further
measured data if necessary
the export of measured data as an image for publication, documentation, etc.
the export of measured data as a .csv file for further processing in Excel, Matlab,
Origin, R, etc.
Hereafter the software's characteristics are described in detail.

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1) Easy and flexible portrayal of the measured data
All measured data can be displayed in both a 2D and 3D diagram.
Figure 16 2D diagram
Figure 17 3D diagram
It does not matter if the measured data was recorded in different frequency ranges. Individual
measurement curves can be displayed or hidden and each curve can be assigned a certain color
or description to provide a better overview. Furthermore, gridlines allow the developer to compare
measurement curves very precisely in the linear or logarithmic 2D diagram.
Figure 18 Data Manager
2) Storage and export of measured data
Any amount of measured data can be stored in a file. This file can be reloaded from ChipScan-
ESA at any time as required. The data can be recorded first and evaluated later. In addition, new
measurements can be compared with older ones.
Any number of measurement plots can be exported optionally as an image or a .csv file to edit the
measured data for publication or documentation. The .csv export allows the developer to process
the measured data using statistical software such as Excel, Matlab, Origin and R.

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3) Fast and easy handling of spectrum analyzers / frequency generators
All the important device settings can conveniently be carried out with the ChipScan-ESA software
and all supported spectrum analyzers can be controlled via a uniform operator interface.
Figure 19 Spectrum Analyzer Setup
In addition, the device settings can also be stored in configuration files and reloaded. This prevents
any operating errors which may occur in measurement logs.
ChipScan-ESA automatically recognizes all (see list of supported devices
1
) measuring instruments
connected to the PC irrespective of the interface used (RS232, GPIB, VXI) even if several
measuring instruments are connected simultaneously. The recognized devices can also be stored
in configuration files and reloaded.
3.3 Localization through global changes to the unit under test
The unit under test often allows you to locate the emission sources by changing the measurement
set-up. These include
a) geometrical changes:
-Changing the distance between the unit under test and ground plate.
-Use sheet steel to simulate neighboring modules or housings.
-Plugging in and removing cables, changing the cable length and position.
-Eliminating individual RF sources by disconnecting individual modules, partial shielding or by
using ferrite magnets.
b) changes to the operating procedure:
-Using another software or program or program section.
-Observing the spectrum when the program is running up.
-Switching off individual sections of the unit under test.
-Operating the unit under test under permanent reset conditions –only the clock line is
maintained.
1
https://www.langer-emv.com/en/product/software/25/cs-esa-set-chipscan-esa-software-cd-
rom/163#Manual05

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3.4 Reason analysis with near field probes
Carry out near-field measurements to exactly determine the RF sources that emit disturbances.
The goal is to correlate the currents measured with the RF current transformer to the RF fields on
the module. You should proceed as shown in Figure 20:
Begin by determining the magnetic and electric
fields in the vicinity of the modules. These
fields incite the whole metal system of the unit
under test to oscillate (exciting fields) and must
finally be reduced. You should use near-field
probes with a bigger probe head, i.e. the probe
RF-R 400-1 for magnetic and the probe
RF-E 02 for electric fields.
These measurements give you an idea of the
respective disturbance emission mechanism.
As a next step, locate the sources of these
exciting fields. The probes with smaller probe
heads such as the RF-R 3-2 magnetic field
probe are particularly suitable for this job.
Figure 20 Field measurement with near-field probes
In each measurement you determine
-the field strength at a certain frequency or within a certain frequency range and
-the direction of the magnetic field lines by rotating the magnetic field probe (magnetic field
measurements).
The following fields should be considered as potential RF sources:
-electric fields above components such as processors
-electric fields on switched lines and bus systems
-magnetic fields on switched data and clock lines
-magnetic fields on power supply lines
Figure 21

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3.5 Modification of the module
There are various starting points for modifying a module:
a) Modifying the module's geometry with regard to
-plug-and-socket connectors and cable connections
-the layout
-the surrounding metal system
b) Changing the circuitry by
-inserting damping resistors, filters
-changing the operating procedure
The RF sources have to be modified so that the field strength is reduced (damping) or the lines of
force are kept in the immediate vicinity of the source and do not exit the module.
Having detected the potential disturbing fields on the module, you will automatically have ideas and
possibilities on how to reduce these fields. Potential modifications are:
- Confining the magnetic fields through metal surfaces
- Shielding electric fields through GND areas
- Inserting damping resistors in signal lines
Perform another measurement with the HFW 21 to check the effect of the implemented
modifications. Evaluate the modification, take other measures if necessary and only carry out a
further acceptance measurement if there is a decisive improvement in the module.

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4 Measurement set-up variants
4.1 Measurement of the common-mode component
4.1.1 Unit under test with one cable terminal
If only one cable, e.g. the power supply cable, is connected to the unit under test, its leads are
filtered first through the GP 23 ground plate and then through the HFW 21 (Input: Power and
output COM). The RF current flows through the parasitic capacitance between the unit under test
and ground plate to the ground plate and back to the unit under test through the HFW 21 via the
power supply cables (Figure 22 and Figure 23).
The distance between the unit under test and
the ground plate influences the magnitude of
the RF current:
- If the unit under test is operated in an open
space (computer mouse on a wooden table),
choose a large distance between the unit
under test and ground plate (> 5 cm).
Figure 22
- If the unit under test is installed near a
metal surface (control system in a washing
machine), simulate this distance.
The scope of delivery includes a foam block
(25 mm high) which you can use as a
distance piece.
Figure 23
The capacitance between the unit under test and ground plate is determined by the size and
distance of the unit under test. The RF current flows through this parasitic capacitance. This may
be caused by electric fields on the surface of the unit under test which are generated by large
surface clocked bus systems.
In some cases it will not be possible for you to pass the single cable through the current
transformer, e.g. if
-more than two wires are needed,
-the current consumption of the unit under test is too high,
-the supply voltage is too high.
In such cases you should connect the unit under test via the usual cable and connect its GND
directly to the ground plate via the HFW 21 by as short a cable connection as possible. A large part
of the RF current which is normally fed to the cable will be diverted via the HFW 21 and measured.
You can make this procedure more effective by inserting a choke into the cable.

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4.1.2 Unit under test with several cable terminals
The aim is a measurement set-up which is as simple and easily comprehensible as possible. All
cables that are not crucial for operating the unit under test are thus disconnected. A restricted
function due to missing data, for example, is generally acceptable because essential RF sources
on the module, such as the clock line and processor, are still operational in this case even if minor
changes arise due to other program sequences, for example. After having found and minimized the
main disturbance emissions causes, carry out respective control measurements and, if necessary,
connect one cable after the other (Figure 24 and Figure 25).
Replacing cables that are not crucial for
operation with a link to the ground plate:
Establish a direct conductive connection
from the GND terminal of the plug-and-
socket connector to the ground plate
instead of the cable in the simplest case.
Figure 24
You can also establish a capacitive
connection from GND or Vcc, for
example, to the ground plate.
Measure the influence of (clocked and
operationally static) data lines via a direct
capacitive connection from these data
lines to the ground plate (also see 4.1.5
External data lines).
Figure 25
4.1.3 Unit under test with indispensable cables
If you cannot disconnect and simulate cables by an equivalent capacitance or conductive
connection for functional reasons, you have to put and fix the cable on the ground plate
(Figure 26). If the cable leaves the ground plate, use ferrites (still on the ground plate) to prevent
the cable position and length outside the defined measurement set-up from interfering with the
measurement result and prevent interference currents, which flow in from the surroundings via
these cables from being damped.
Figure 26

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4.1.4 Example: Measurements on a complex unit under test
In many cases, different effects of various RF sources within the unit under test will first be
superposed and lead to an amplification or reduction of the RF fields at particular frequencies. It is
therefore important for an effective reason analysis, particularly with complex units under test
comprising several modules, to dismantle the unit under test and deal with individual modules
separately.
The unit under test shown in Figure 27 has several potential disturbance emission sources. We
only consider here the interface module plugged on to the basic unit as an example:
Figure 27 RF sources on the interface module
Three RF sources are likely to cause emissions:
1) plug-and-socket connector between basic unit and interface module
2) electronic components (processor with memory chip) on the interface module
3) data streams generated by the interface module and fed into the connected cable
Deal with these three RF sources in succession. You will need measurement set-ups that largely
blank out the other RF sources of the unit under test and those of the basic unit.
1) Plug-and-socket connector between basic unit and interface module
Assumption:
The basic unit and interface module are connected to each other via data and control lines. These
lines are well protected by the basic unit and interface module in the area of the GND systems –
but in the area of the plug-and-socket connector they lie in the open air. The high-frequency shares
of the signals sent via these lines generate RF magnetic fields which can dissipate freely in the
atmosphere and can cause voltage differences between the GND of the basic unit and that of the
interface module. These voltage differences drive RF currents into the cable that is connected to
the interface module and thus cause emissions (Figure 28).
All other potential RF sources have to be largely eliminated to measure these voltage differences.
To do so, make several connections between the GND of the basic unit and the GP 23 ground
plate with copper foil adhesive tape (mainly in the area of the interface module). The basic unit's
GND in the area of the interface module and the ground plate are thus equipotential –the voltage
differences caused by other sources are short-circuited to the greatest possible extent. Also
disconnect the data cable from the interface module provided the data transfer between interface
module and basic unit is not dramatically reduced by this measure.

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Measurement:
Now briefly connect a COM output of the HFW 21 with the GND of the interface module
(Figure 28). The voltage difference generated in the area of the plug-and-socket connector causes
a compensating current to flow through HFW 21 and its capacitive connection to the ground plate
back to the GND of the basic unit. This compensating current is measured with the HFW 21 and
reflects the amount of the plug-and-socket connector area's share of disturbances being emitted by
the whole unit under test. The effects of modifications such as filters or changing the plug
assignment are directly measurable.
Figure 28 GND of the interface module connected to the COM output of the HFW 21
2) Electronic components (processor with memory chip) on the interface module
Assumption:
The electronic components on the interface module generate currents in the GND system of the
interface module which provoke a voltage drop between the connection points of the two plug-and-
socket connectors. This voltage difference is decoupled via the data cable and causes disturbance
emissions.
Measurement:
The basic unit is still connected to the GP 23 ground plate. The remaining share of the plug-and-
socket connector between interface module and basic unit is dramatically reduced by several
large-area GND connections between both GND surfaces (Figure 29).

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Figure 29 Evaluation of the modifications with the HFW 21
Tap the voltage directly at the GND terminal of the interface plug via a short measuring cable to the
COM port of the HFW 21. Thus the modifications that have been made directly on the interface
module can be evaluated.
3) Data streams fed into the connected cable
Assumption:
The interface driver module feeds a RF current into the signal wires of the data cable. This current
couples to the shield via the cable capacitance of signal wire - shield and flows back to the GND of
the interface module. It generates a voltage difference between the shield and GND in the area of
the shield connection which causes disturbances being emitted.
Measurement:
Carry out this measurement without changing the measurement set-up. Simply connect the
HFW 21 directly to the shield of the plugged-in data cable (Figure 30). Thus the voltage drop can
be detected as expected.
Figure 30 HFW 21 detects the voltage drop on the shield of the connected data cable