Table of Contents
Introduction 2
Specification 3
EMC 5
Safety 6
Installation 8
Connections 8
Operation 9
Maintenance 14
Instructions en Francais
Introduction 15
Sécurité 16
Installation 18
Connexions 18
Fonctionnement 19
Maintenance 24
Bedienungsanleitung auf Deutsch
Einführung 25
Sicherheit 26
Installation 28
Anschlüsse 28
Betrieb 29
Wartung 34
Istruzioni in Italiano
Introduzione 35
Sicurezza 36
Installazione 38
Collegamenti 38
Funzionamento 39
Manutenzione 44
Instrucciones en Espanol
Introducción 45
Seguridad 46
Instalación 48
Conexiones 48
Funcionamiento 49
Mantenimiento 55
1
Introduction
The Aim I-prober 520 is a unique device which is capable of observing and measuring current in PCB
tracks and other locations where conventional current probes cannot be used. It is a ‘positional’
current probe which derives its measurement from the magnetic field at a defined position relative to
the current carrying conductor. This enables current observation and measurement from simply
placing the insulated tip of the probe onto a PCB track, component leg or ground plane.
A clip-on toroid attachment is also provided which converts the probe into a more conventional ‘closed
magnetic loop’ current probe when required.
This current probe employs a sensing method generally known as a fluxgate magnetometer, and
measures the magnetic field surrounding the electric current. The magnetometer consists of a small
coil of wire surrounding a core made of an advanced material with special magnetic properties. An
excitation current (at approximately 40MHz) is passed through the coil, which magnetises the core
alternately in opposite directions. If there is no external magnetic field, this magnetisation is
symmetrical. When an external field is applied, the resulting asymmetry is detected by a feedback
loop which applies an opposing current through the coil to restore the net field to zero. The output
voltage is proportional to this opposing current, and therefore to the magnitude of the field.
The unique feature of this probe is the very small size of the magnetometer element, which allows
fields to be measured at an accurately localised position in space, and also allows the signal
bandwidth to extend from DC up to 5MHz. Two lower bandwidth settings are also provided, which
give lower noise.
Unlike transformer based probes, which are either AC coupled only or require a separate mechanism
(such as a Hall effect device) to provide a response down to DC, this probe uses the same
measurement mechanism for all frequencies across its bandwidth.
It is intended for use with an oscilloscope with a standard 1MΩ input impedance.
2
Bandwidth (small signal):
DC to 5MHz.
Pulse Rise-time (10% - 90%):
<70ns.
Propagation delay:
60ns typical.
Pulse aberrations:
<±5% (<1% at lowe r bandwidth settings).
Slew Rate (equivalent):
15A/µs
6mA
rms
; 1.5mA
rms
at minimum bandwidth setting.
Filter settings:
Full bandwidth, 500kHz or 2Hz.
Scaling factor:
250µT (or 200A/m) per output Volt
Accuracy and linearity:
±3%
Maximum field:
±2·5mT (2000A/m)
Current range:
±10mA to ±10A (DC + peak).
Accuracy and linearity:
±5%
Scaling factor:
1 Amp per output Volt.
Maximum wire diameter:
3.5mm (unbroken) or 6mm (end fed).
adjusted to suit track width):
2 Amp per Volt for track widths 3mm to 6.5mm (0·125” to 0·25”)
Maximum output voltage:
±10V, corresponding to ±2·5mT (field measurement) or ±10A (wire)
Maximum Permitted Transient Overvoltage: 2500V.
150ºC
Probe dimensions:
155mm x 38mm x 28mm max; 2.8mm x 1.8mm at tip
Cable length:
2m from probe tip to output BNC
Safety:
Complies with EN61010-1 & EN61010-031
EMC:
Complies with EN61326
General specifications apply for the temperature range 5°C to 40°C with the probe connected to a
measuring instrument (oscilloscope or DMM) having an input impedance of 1MΩ || <30pF . Accuracy
specifications exclude errors of that measuring instrument and apply for the temperature range 18°C
to 28°C after 30 minutes warm-up and calibration at 23°C. Specifications quoted without limits are
typical characteristics determined by design and are not guaranteed.
Dynamic Characteristics
Noise (equivalent in toroid):
Magnetic Field Measurement
Specification
Current measurement in wire (with toroid attachment)
Current measurement in PCB track
Scaling factor (with control
1 Amp per Volt for track widths 0·2mm to 3.5mm (0·007” to 0·14”) or
General characteristics
Maximum bare-wire voltage:
Maximum track temperature: The maximum temperature of a surface on which the probe
300V
600V
measurement tip can be placed for short periods (2 mins max) is
CAT II (circuits connected directly to the low voltage mains) or
rms
CAT I (circuits not connected directly to the low voltage mains).
rms
3
Performance levels achieved are detailed in the user manual.
EC Declaration of Conformity
We Thurlby Thandar Instruments Ltd
Glebe Road
Huntingdon
Cambridgeshire PE29 7DR
England
declare that the:
I-prober 520 Current Probe
meets the intent of the EMC Directive 2004/108/EC and the Low Voltage Directive 2006/95/EC.
Compliance was demonstrated by conformance to the following specifications which have been listed
in the Official Journal of the European Communities.
EMC – I-prober 520 Current Probe + AC Power Adaptor
Emissions: a) EN61326-1 (2006) Radiated, Class A
b) EN61326-1 (2006) Conducted, Class B
c) EN61326-1 (2006) Harmonics, referring to EN61000-3-2 (2006)
Immunity: EN61326-1 (2006) Immunity Table 1, referring to:
a) EN61000-4-2 (1995) Electrostatic Discharge
b) EN61000-4-3 (2006) Electromagnetic Field
c) EN61000-4-11 (2004) V oltage Interrupt
d) EN61000-4-4 (2004) Fast Transient
e) EN61000-4-5 (2006) Surge
f) EN61000-4-6 (2007) Conducted RF
Safety – I-prober 520 Current Probe
EN61010-1, EN61010-031 & EN61010-2-032, Pollution Degree 2.
Safety – AC Power Adaptor
EN60950-1
CHRIS WILDING
TECHNICAL DIRECTOR
1 March 2011
4
This Current Probe has been designed to meet the requirements of the EMC Directive 2004/108/EC
when operated with the supplied AC Power Adaptor.
Compliance was demonstrated by meeting the test limits of the following standards:
Emissions
EN61326-1 (2006) EMC product standard for Electrical Equipment for Measurement, Control and
Laboratory Use. Test limits used were:
a) Radiated: Class A
b) Conducted: Class B
c) Harm onics: EN61000-3-2 (2006) Class A; the instrument is Class A by product category.
Immunity
EN61326 (2006) EMC product standard for Electrical Equipment for Measurement, Control and
Laboratory Use.
Test methods, limits and performanc e achieved are shown below (requirement shown in brackets):
a) EN61000-4-2 (1995) Electrostatic Discharge: 4kV air, 4kV contact, Performance A (B).
b) EN61000-4-3 (2006) Electromagnetic Field:
c) EN61000-4-11 (2004) V oltage Interrupt:
d) EN61000-4-4 (2004) Fast Transient:
e) EN61000-4-5 (2006) Surge: 0·5kV (line to line), 1kV (line to ground), Performance A (B).
f) EN61000-4-6 (2007) Conducted RF:
†
Signal connections were not tested on the basis that they are <3m, for which there is no test
requirement.
EMC
3V/m, 80% AM at 1kHz, 80MHz – 1GHz: Performance B
2GHz: Performance A (A); 1V/m, 2.0GHz to 2.7GHz: Performance A (A).
*Note: The current probe is a sensitive measuring instrument that, by design, measures
magnetic fields. The sensor will respond to a sufficiently large RF field and a measurement
being made might be disturbed, particularly if the current level being measured is small. In all
other respects the instrument will operate correctly (Performance A) in fields up to 3V/m.
½-cycle, 0%: Performance A (B); 1 cycle, 0%: Performance A(B);
25 cycles, 70%: Performance A(C); 250 cycles, 0%: Performance B(C).
1kV peak (AC line only; signal connections <3m, therefore not tested
3V, 80% AM at 1kHz (AC line only; signal connections <3m, therefore not tested
A ( A).
*
(A) and 1.4GHz to
†
), Performanc e B (B).
†
), Performance
Performance Definitions
The definitions of performance criteria are:
Performance criterion A: ‘During test normal performance within the specification limits.’
Performance criterion B: ‘During test, temporary degradation, or loss of function or performance
which is self-recovering’.
Performance criterion C: ‘During test, temporary degradation, or loss of function or performance
which requires operator intervention or system reset occurs.’
5
Current Probe
This instrument is Safety Class III according to IEC classification and has been designed to meet the
general requirements of EN61010-1 (Safety Requirements for Electrical Equipment for Measurement,
Control and Laboratory Use) and sub-part EN61010-031 as applied to this particular form of current
probe.
This instrument has been tested in accordance with EN61010-1 and EN61010-031 and has been
supplied in a safe condition. This instruction manual contains essential information and warnings
which have to be followed by the user to ensure safe operation and to retain the instrument in a safe
condition.
This instrument has been designed for indoor use in a Pollution Degree 2 environment in the
temperature range 5°C to 40°C, 20% - 80% RH (non-condensing). It may occasionally be subjected
to temperatures between +5° and -10°C without degradation of its safety. Do not operate while
condensation is present.
• Use of this instrument in a manner not specified by these instructions may impair the safety
protection provided.
• This probe may only be used by qualified personnel who are aware of the risks associated
with probing on or near bare conductors at hazardous voltages, i.e. voltages above 70Vdc or
ac voltages exceeding 33Vrms or 46.7Vpeak. The maximum voltage of bare conductors on
which it can be used is 300Vrms CAT II or 600Vrms CAT I.
WARNINGS and CAUTIONS
Safety
• The maximum temperature of a surface on which the probe measurement tip can be placed
for short periods (2mins max) is 150
temperatures.
• Connect the AC Power Adaptor to the Base-box and the signal output BNC cable to the
oscilloscope before the probe is put in contact with the signal to be measured. Only use the
AC Power Adaptor supplied and always use an oscilloscope which has its chassis connected
to earth ground.
• Inspect the probe tip, casing and cabling for wear and damage before every use. Safety
depends entirely on the integrity of the insulation of that section of the probe shaft forward of
the raised safety marker, and of the probe tip in particular.
DO NOT USE THE PROBE IF AN Y PART APPEARS TO BE DAMAGED
See Maintenance section for details of where to return damaged probe assemblies.
Do not dismantle the probe or its base-box – there are no user-serviceable parts.
• Do not hold the probe beyond the finger guard between the body and the probe shaft when
making a measurement on a conductor which is at a hazardous voltage, and do not allow any
hazardous voltage to approach any closer to the finger guard than the safety marker on the
probe shaft. See the diagram opposite.
• Before attaching or detaching the toroid assembly from a bare cable at a hazardous voltage
make sure that the conductor is not energized.
• Do not use the probe when wet or if condensation is present. Do not wet the instrument when
cleaning it.
o
C. Do not expose any other part of the probe to high
AC Power Adaptor
The adaptor/charger supplied has a universal input voltage rating of 100-240VAC, 50/60Hz. It is a
Class II (double insulated) device, fully approved to EN 60950-1 (2001) and UL 60950 (UL listing
E245390).
6
bus-bars, etc., or industrial installations, all of which are classified as CAT III.
Symbols
The following symbols are used on the current probe and in this manual.
WARNING – Risk of electric shock.
CAUTION – refer to accompanying documentation (this manual).
Damage to the instrument may occur if these precautions are ignored.
Do not apply around or remove from hazardous live conductors.
Application to hazardous live conductors acceptable.
Protected throughout by double insulation or reinforced insulation.
alternating current (ac).
direct current (dc).
CAT II
CAT I
Indicates Measurement Category II; the maximum voltage rating to earth for CAT II
measurements is generally shown with the symbol. Measurement Category II
applies to measurements performed on circuits directly connected to the low-voltage
mains supply, e.g. portable equipment and appliances. CAT II does not include
measurements on distribution level circuits, e.g. distribution boards, circuit-breakers,
Indicates Measurement Category I; the maximum voltage rating to earth for CAT I
measurements is generally shown with the symbol. Measurement Category I
applies to measurements performed on circuits not directly connected to the lowvoltage mains supply. This category includes secondary circuits separated from the
mains circuits by a transformer and circuits derived from the mains supply in which
measures have been taken to limit transient over voltages to an appropriately lower
level. The maximum permitted transient overvoltage for the 600V CAT I rating of
this probe is 2500V.
7
Always inspect the probe tip for wear before use on conductors at hazardous voltages.
Installation
Mains Operating Voltage
This instrument is supplied with an AC power adaptor which has a universal input range and which will
operate from a nominal 115V or 230V mains supply at 50Hz or 60Hz without adjustment. Check that the
local supply meets this AC Input r equirement.
Fit the required national power connector to the adaptor by sliding it down the grooves until it locks.
The unit may only be used with the power adaptor supplied.
Disconnect the power adaptor from the supply when the unit is not in use.
The AC adaptor is a Safety Class II (double-insulated) device providing 5.2VDC at up to 1Amp. The
ground reference for the measurement system is the ground connection made to the scope. Always use
a scope which has a grounded chassis so the outer of the BNC is connected to ground.
General Installation Considerations
When used without the toroid attachment (for current in a wire) the probe will be influenced noticeably by
all external magnetic fields at the point of measurement – not only the earth's magnetic field (which may
be modified by steel metalwork) but leakage fields from inductors or transformers, magnetised
components, etc. The Operation section contains useful notes on how to achieve the best qualitative and
quantitative measurements in the various operating modes in the presence of such stray fields.
Connections
Power connection
Fit the required national power connector to the supplied adaptor by sliding it down the grooves until it
locks and connect the adaptor to the AC supply. Connect the output lead from the adaptor to the power
input socket of the control box, marked DC IN.
The unit may only be used with the power adaptor supplied.
Output signal
Connect the BNC connector on the captive output lead from the control box (marked OUTPUT) to a 1MΩ
scope input. This lead is sensitive to loading capacitance and should not be extended if accurate
reproduction of the waveform shape is required. Always use a scope which has a grounded chassis so
the outer of the BNC is connected to ground, and make this connection before probing high voltages.
The scope Y -axis sensitivity can be set to suit the magnitude of the field being investigated. AC coupling
can be used to remove the effect of the earth's magnetic field, or other fixed fields from permanently
magnetised material, provided they are not so large as to overload the probe.
Measurement Connection
The cable between the probe unit and the control box is captive at both ends and cannot be replaced by
the user. Care should be taken to ensure it does not come into contact with hot objects.
The measurement of current is effectively ‘non-contact’; no galvanic connection is made to the currentcarrying conductor being probed. The probe tip and the probe shaft forward of the raised safety barrier
are double-insulated and it is possible to probe safely onto conductors at high voltages with respect to
earth ground, up to the limits stated in the Specification. However, it is imperative that the insulation of
the probe tip has not been damaged by abrasion or by contact with hot surfaces above 150°C.
Read and understand the Safety section of this manual before use.
Measurements on apparatus with dangerous voltages exposed should only be made by
engineers with sufficient training and experience to recognise the hazards involved.
8
Operation
Controls
The following controls are mounted on the control box.
Mode Switch
This three position slide switch adjusts the probe gain to obtain calibrated results in the three main
operating circumstances: FIELD Measurement of magnetic field.
PCB TRACK Measurement of the current in a PCB track underneath the probe tip.
WIRE Measurement of the current in a wire or cable, in conjunction with the toroid
attachment.
Sensitivity
This control is active in the PCB TRACK position only, and is used to adjust the gain to suit the physical
width of the track being measured.
Trace position
This control adjusts the DC offset in the output signal to compensate for fields such as the earth's
magnetic fields. At high sensitivities this control has much more range than the Y posit ion control of most
scopes.
Bandwidth Switch
This three position switch allows the user to choose the best compromise between signal bandwidth and
noise level. The three bandwidths are nominally 5MHz, 500kHz and 2Hz. The 2Hz position will almost
totally remove any visible effect of mains frequency fields at 50 or 60 Hz, but note that it is possible for the
probe to be invisibly overloaded by a large field at frequencies above the bandwidth limit.
Calibrator Switch
With the probe inserted into the calibration hole until it contacts the PCB it is subjected to the field from a
known current. The three position switch allows the selection of an AC (1kHz square wave) or DC current,
with the centre position being off. The procedure for using this to calibrate the sensitivity of the probe to
suit a particular track width is detailed below.
The calibration current should be switched off when not in use.
Overload indicator
The overload indicator will light either if the signal exceeds the clipping level of the output amplifier, or if
the magnetic field is so large that the system is saturated, which can cause the output signal to appear to
be within the operating range. In particular, this indicator should be monitored if AC coupling is used on
the scope, as it is still possible for DC fields to overload the probe.
Magnetic Field Measurements
The magnetic field is measured along the wider dimension of the probe tip. The scaling factor is 250µT
(micro-Tesla) per Volt, so the normal scope setting sequence gives 250µT/div at 1V/div, 500µT/div at
2V/div, and 1. 25mT/ div at 5V/div. More sensitive decades scale as expected. 250µT is 2.5 Gauss.
Alternatively the scale factor can be regarded as 200 Amps-per-metre per Volt, so the corresponding
scale factors are 200A/m/div, 400A/m/div and 1000A/m/div.
In either case the maximum output voltage is ±10V, corresponding to the maximum working field of
±2.5mT or ±2000A/m.
If the probe is held tip down (handle uppermost) with the
to give a positive output voltage, then the lines of flux are passing from a North pole on the left to a South
pole on the right. In the earth's magnetic field this means that geographic North is on the right.
9
+ sign on the barrel facing the user, and oriented
adequately insulated for the voltage it is carrying, or by disconnecting it from its supply.
Application Notes for Magnetic Field Measurements
Because of the very small dimensions of the probe tip, the probe is capable of investigating the variation
of magnetic fields over very localised areas. It can investigate the fields around inductors and the gaps in
their cores, which can sometimes cause unexpected cross-talk into an electronic circuit. It can also show
the fields radiating through any slots and holes in an equipment case, which are often the source of EMC
compatibility problems. The probe has a bandwidth which covers most of the waveforms in switched
mode power supplies.
The low noise of the system makes it capable of measuring fields much smaller than the earth's field,
which at high scope sensitivity settings can take the trace a long way off screen. The TRACE POSITION
adjustment on the control box has much more range that the typical Y-shift control of a scope. In many
instances, AC coupling of the scope can be used, which will minimise the inconvenience if the low
frequency distortion of the waveform is acceptable.
Measurements of current in a wire
A toroid attachment is provided to allow measurement of the current flowing in a wire or cable. This
attachment contains a magnetic core which concentrates the field from around the cable onto the sensor
of the current probe. It mechanically locks onto the nose of the probe to hold the correct relationship
between the gap in the toroid and the sensor in the probe tip.
Attaching the Toroid to the Cable
Before attaching the toroid assembly to the cable to be measured, first ensure that
there is no risk of electric shock to the operator by either making sure that the cable is
Pass the cable through the open end of the jaws of the toroid housing, then align the probe so that the
large pips on the nose are aligned with the gaps in the housing and push them together in a straight line.
The jaws of the attachment are forced apart as the nose of the probe passes through until they lock (with
an audible click) into the locating slots. Confirm that the two parts are securely locked together by gently
rotating and pushing the probe. For calibrated results arrange the cable to be at the back of the hole in the
toroid, away from the sensing tip of the probe.
Select the Wire position on the MODE switch on the Control Box. This gives a calibrated sensitivity of 1
Volt per Amp. Set the scope Y-axis sensitivity as required and select a suitable BANDWIDTH setting.
Note: The 1 V/A calibration only applies to a matched set of probe and toroid. The toroid
attachments are not interchangeable between probes. Check that the serial numbers of probe and
toroid match to ensure that the pairing being used is calibrated.
Operating Notes for Using the Toroid Attachment
The mag netic circuit of the toroid reduces the sensitivity to external magnetic fields (including the earth's
field) by a factor of about five, so the measurement is much less affected by positioning of the probe;
nevertheless, for best measurement consistency, arrange for the probe to rest in a fixed position away
from strong local fields.
Additional sensitivity can be obtained by winding multiple turns of the wire around the toroid. The
resulting increase in insertion inductance will impair the frequency response slightly, and might affect
some high frequency circuits, but otherwise the scaling factor is multiplied by the number of turns.
When measuring DC, the measurement can be affected by small hysteresis and remanence effects in the
magnetic material of the toroid. For best accuracy, first apply the current in the required direction to prebias the magnetic circuit, then remove the current and adjust the TRACE POSITION control to set the
zero point on the scope; then reapply the current to measure it. T his zero point will not change much as
the current varies providing it remains in the same direction. If, however, the polarity of the current is
reversed, the zero should be reset. When measuring alternating current this effect is negligible, but note
that when the current is switched off the zero point may exhibit some offset.
The polarity marks on the probe barrel are the reference for indicating the direction of the current: the
output to the measurement instrument will be positive when the current flows from the side with the
10
+
Measurements on apparatus with dangerous voltages exposed should only be made by
take care to keep the hands away from high voltages.
mark to the side with the – mark. There are also polarity marks on the toroid attachment, but these are
only to assist in consistent attachment; reversing the toroid does not reverse the polarity.
Removing the Toroid
To remove the toroid, hold both the toroid attachment and the probe body and gently twist through about
30º while pulling the two apart. The twisting action uses the lugs on the nose of the probe to lever the
arms of the toroid housing apart, which makes removal much easier than a straight pull.
Before touching the toroid, ensure that there are no dangerous voltages present.
Measurement of Current in a PCB Track
Before touching the probe onto tracks carrying high voltages, always check the condition of the
tip insulation. The probe tip is double-insulated; underneath the black, high melting-point, ‘wear-tip’
moulding is a second light coloured moulding containing the sensor itself. If the light coloured inner
moulding can be seen then the probe is no longer safe for high voltage use. Careful inspection is needed,
as dirt or ragged wear might make the colour difference hard to detect. To maximise the lifetime of the tip,
avoid rubbing it across rough surfaces.
engineers with sufficient training and experience to recognise the hazards involved. Always
The probe measures the current in a PCB track by measuring the magnetic field around the track caused
by the current. The probe must be held centred over the track, with the long dimension of the probe tip
across the track and the probe body held as close to perpendicular to the track as possible. When the
output is positive on the measurement instrument then the current is flowing in the direction
indicated by the + and – marks on the probe barrel. Because this is not a magnetically closed circuit the
probe will also be influenced by all external magnetic fields at the point of measurement. There are many
causes of such fields – the earth's magnetic field (which may be modified by steel metalwork), leakage
fields from inductors or transformers, magnetised components (such as screws) and even magnetic
materials in the electrodes or terminations of electronic components. As a result, it is quite difficult to
make accurate quantitative measurements, but there are many applications where a qualitative
measurement gives all the information required.
+ to –
Qualitative Measurements
Major areas of application for this probe are in switched mode power supplies, power amplifiers or other
circuits where high currents flow. The probe is optimised for waveform fidelity, and the fact that its
response extends down to DC allows exact wave shapes to be viewed. Its very localised nature allows
detailed investigation of the exact paths these currents take.
It can, for example, be used to investigate the effectiveness of reservoir or decoupling capacitors – a
pulsed current should flow between the switching device or rectifier and the capacitor, and only a DC
component should flow from the other side of the junction. Residual switching signals, caused by
improper layout or inadequate components, can be easily seen.
The probe can be particularly useful in investigating the current flow in power and ground planes. It is
often found that if a ground plane is split and then re-joins, perhaps around a group of components, then
an unexpected circulating current can be induced around the resulting loop. It can also be used to show
radiation and cross coupling between circuits, and to check for proper cancellation in circuits which are
supposed to be balanced.
Another application is in finding short circuits on a PCB, where the current can be followed from its source
to the point where it is diverted through the fault. Comparing the signal with the current switched on and
off can distinguish between the fault current and external magnetic fields.
Currents can be measured not only in PCB tracks but also in component leads, including the terminals of
integrated circuits. Take care to avoid very hot components, such as wire wound resistors, which can
exceed the temperature rating of the probe tip.
11
I- pr ober 520 PCB sensitivi t y setti ng
For 1 Amp/Volt
For 2 Amp/Volt
Calibrator output (Vpp)
Track Width ( mm)
3.5
4
3
2.5
2
1.5
1
0.5
0
0 1 2 3 4
5
6
7
Calibration for Quantitative Measurements on PCB tracks
The relationship between the output voltage seen on the scope and the actual current in the PCB track
depends on a complex relationship between the width of the track, the width of the sensor inside the
current probe, and the thickness of the probe insulation between the track and that sensor. To obtain
quantitative measurements the sensitivity adjustment on the control box must set to suit the particular
track width being measured. The wider the track, the lower the field strength for a given current, so the
greater the gain required to obtain a sensitivity of 1A/V. At track widths above about 3.5mm the control
box gain cannot be increased sufficiently to give a sensitivity of 1A/V so the system must be adjusted for
a sensitivity of 2A/V.
This relationship between track width and the gain required is incorporated into the calibration graph
below. The calibration procedure involves placing the probe into the calibration hole in the control box
and applying the calibration current. The sensitivity control is then adjusted to obtain the particular output
voltage (as measured by the scope trace) to suit the intended track width. The calibrator can produce
either a square wave or DC calibration current. To avoid difficulties caused by the influence of the earth's
magnetic field and the local magnetic environment, calibration is normally performed using the square
wave signal, obtained by setting the switch to the AC (
1kHz. The amplitude setting refers to the peak-to-peak voltage between the flat parts of the square wave,
ignoring any overshoot on the transitions.
Detailed Procedure
) position. The signal is a square wave at about
First, decide on the width of the track for which a calibrated measurement is required. Then, using the
graph, look up the peak-to-peak output voltage setting for that track width and set the scope to a suitable
sensitivity (for example, 1 Volt per division for narrow tracks, or 0.5 Volt per division for wider tracks).
12
Insert the probe into the calibration recess and turn on the calibration signal by setting the CALIBRATOR
switch to the AC position (marked
). Optimise the orientation of the probe within the calibrator recess to
obtain the maximum signal amplitude on the scope, then adjust the Trace Position control to centre the
trace on the screen.
Adjust the PCB Sensitivity control so that the peak-to-peak voltage of the scope trace (ignoring
overshoot) equals the value obtained from the calibration graph for the required track width. The probe
sensitivity is now set to give either 1A/V or 2A/V (depending on which calibration curve is used) for
measurements on the actual PCB track.
Switch off the calibration signal by returning the CALIBRATOR switch to its centre position.
For tracks wider than 6.5mm, it can be assumed that the reading is inversely proportional to the track
width plus 2.2mm. Alter natively, switch to Magnetic Field mode and measure the field in Amps per metre.
This can be converted to Amps, by assuming that the path length is twice the width of the track plus
4.4mm (this figure accounts for the fact that the sensor is 0.7mm above the track surface). This
relationship assumes that the track is long in relation to its width and reasonably uniform in layout.
Practical Aspects of Quantitative Measurements
To accurately measure the current in a track the probe must be
precisely positioned vertically in two dimensions, placed exactly
above the centre of the track and aligned with the long dimension of
the tip at right angles to the track.
The diagram shows the proper orientation. If the probe is not aligned
at right angles across the track (yaw), the output varies according to a
sine law, so small errors are tolerable; similarly, rotating the probe
forwards or backwards around its rounded tip (pitch) does not cause
major errors. The most critical position requirements are the centring
over the track, and being vertical side to side (roll), so that the probe
is flat on the track, not canted up on the corner of its tip.
Avoid the temptation to manipulate the probe tip with the
fingers, unless it is certain that there are no dangerous
voltages present.
In the absence of uneven extraneous fields the correct position is the one giving the greatest output but it
will be found that, in an environment containing many magnetic materials, the localised magnetic field can
vary substantially in both magnitude and direction from the earth's North-South field that exists in free
space. As a result, even small movements in the position of the probe can have a significant effect on the
residual output voltage. The best way to minimise the effect of this is to place the probe in the required
location on the track to be measured, switch the current off and set the zero position, then switch the
current on and note its magnitude. Many of these difficulties can be avoided if an AC measurement is
possible.
When measuring small currents (small in relation to the effect of the magnetic field of the local
environment) it is helpful if the probe can be held fixed in space (by using a retort stand or similar device)
and moving the signal being tested under the fixed probe.
Note that the calibration procedure given above only gives accurate results when the measurement is on
an isolated track some distance from any other current. Adjacent tracks carrying currents, including those
on the other side of the PCB, will have a significant effect on the measurement. Obtaining a quantitative
result in such circumstances requires mathematical analysis from first principles.
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The Manufacturers or their agents overseas will provide a repair service for any unit developing a
fault.
Cleaning
If the instrument requires cleaning use a cloth that is only lightly dampened with water or a mild
detergent.
WARNING! TO AVOID ELECTRIC SHOCK, OR DAMAGE TO THE INSTRUMENT, NEVE R ALLOW
WATER TO GET INSIDE THE CASE. TO AVOID DAMAGE TO THE CASE NEVER CLEAN WITH
SOLVENTS.
Tip Insulation
If the insulation of the probe tip becomes worn or damaged so that the inner layer of insulation shows
through, contact the Manufacturers or their agents overseas.
Calibration
The fundamental calibration parameter is magnetic field; calibration requires a calibrated field from a
precision Helmholtz coil. The manufacturer can provide a suitable re-calibration service in the event
that the local calibration service is unable to do so.
Maintenance
However, if only a current-in-wire re-calibration (with the toroid attachment) is required, this can be
achieved using a more widely available standard DMM calibrator. Calibration is performed using a 50
or 60Hz sine wave. Take care to establish a repeatable position of the cable within the opening in the
toroid; this is normally opposite the probe tip and as far back as possible.
Web link
For support please visit www.aimt t i. com.
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Introduction
Le Aim I-prober 520 est un appareil unique capable d'observer et de mesurer le courant dans les
pistes de circuit imprimé et autres emplacements où les sondes de courant conventionnelles ne
peuvent pas être utilisées. Il s’agit d’une sonde de courant “d'alignement” qui tire ses mesures du
champ magnétique à un emplacement bien défini par rapport au conducteur porteur de courant. Ceci
permet l'observation et la mesure du courant en plaçant simplement la pointe isolée de la sonde sur
la piste d'un circuit imprimé, la colonne d'un composant ou un plan de masse.
Un joint torique à agrafe est également fourni, qui convertit la sonde en sonde de courant
"magnétique fermé" plus conventionnelle quand cela est nécessaire.
Cette sonde de courant emploie une méthode de détection généralement connue sous le nom de
magnétomètre à vanne de flux. Elle mesure le champ magnétique entourant le courant électrique. Le
magnétomètre se compose d'une petite couronne de fil entourant un noyau en matériau de pointe
doté de propriétés magnétiques spéciales. Un courant d'excitation (de 40 MHz environ) est passé à
travers la bobine, qui magnétise le noyau par alternance dans des directions opposées. S'il n'y a
aucun champ magnétique externe, cette magnétisation est symétrique. Quand un champ externe est
appliqué, l'asymétrie obtenue est détectée par une boucle de réaction qui applique un courant
opposé à travers la bobine afin de restaurer le champ net sur zéro. La tension de sortie est
proportionnelle à ce courant opposé et donc à la magnitude de ce champ.
La caractéristique unique de cette sonde est la taille minuscule du magnétomètre, qui permet de
mesurer des champs dans une position localisée avec précision dans l'espace, et qui permet
également à la largeur de spectre du signal de s'étendre du CC jusqu'à 5 MHz. Deux paramètres de
la largeur de spectre inférieure sont également fournis, qui offrent un niveau sonore moindre.
Contrairement aux sondes à transformateur, qui sont couplées en CA uniquement ou qui nécessitent
un mécanisme séparé (comme un appareil à effet Hall) afin d'envoyer une réponse au CC, cette
sonde utilise le même mécanisme de mesure pour toutes les fréquences sur sa largeur de spectre.
Elle est destinée à un usage combiné avec un oscilloscope doté d'une impédance d'entrée standard
de 1 MΩ.
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Sonde de courant
Cet appareil est de Classe de sécurité 3 suivant la classification CEI et il a été conçu pour satisfaire
aux prescriptions générales de la norme EN 61010-1 (Règles de sécurité pour appareils électriques
de mesurage, de régulation et de laboratoire) et des sous-partie EN 61010-031, telles qu'elles sont
appliquées à cette forme particulière de sonde de courant.
Cet appareil a été soumis à des essais conformément aux normes EN 61010-1 et EN 61010-031, et il
a été fourni en parfait état de sécurité. Le présent manuel d'instructions contient des informations
essentielles et des avertissements que l'utilisateur doit suivre afin d'assurer une utilisation sans
danger et de conserver l'appareil dans un parfait état de sécurité.
Cet appareil a été conçu pour être utilisé en intérieur, dans un environnement de pollution de degré 2,
dans une plage de températures de 5 °C à 40 °C, entre 20 % et 80 % d’humidité relative (sans
condensation). Il pourra être ponctuellement soumis à des températures comprises entre +5 et 10 °C, sans dégradation de sa sécurité. Ne pas l'utiliser dans une situation de condensation.
• Utiliser cet appareil d’une manière non spécifiée par les présentes instructions risque
d'affecter la protection de sécurité fournie.
• Cette sonde ne doit être utilisée que par un personnel qualifié qui a connaissance des risques
associés à des mesures nues sur ou près de conducteurs sous tension dangereuse, à savoir
des tensions supérieures à 70 V CC ou des tensions CA dépassant 33 Vrms ou 46,7 V en
crête. La tension maximale de conducteurs nus sur lesquels elle peut être utilisée est de
300 Vrms CAT III ou 600 Vrms CAT I.
• La temperature maximale de toute surface sur laquelle la pointe de mesure de la sonde peut
être placée pour de courtes périodes (2 minutes maximum) est de 150
toute autre partie de la sonde à des températures élevées.
• Connecter l'adaptateur d’alimentation CA à la caisse de base et le câble BNC de sortie du
signal à l'oscilloscope avant de mettre la sonde en contact avec le signal à mesurer. Utiliser
seulement l'adaptateur d’alimentation CA fourni et toujours utiliser un oscilloscope ayant son
châssis branché sur la prise de terre.
• Inspecter la pointe de la sonde, le boîtier et le câblage pour détecter tout signe d'usure ou
d'endommagement avant chaque utilisation. La sécurité dépend entièrement de l'intégrité de
l'isolation de cette section de l'arbre de sonde à l'avant du marqueur de sécurité surélevé et
de la pointe de la sonde en particulier.
NE PAS UTILISER LA SONDE SI UNE DES PARTIES SEMBLE ENDOMMAGÉE
Voir la section Maintenance pour plus de détails sur l'adresse où renvoyer des sondes
endommagées.
Ne pas démonter la sonde ni sa caisse de base : elles ne contiennent aucune pièce dont
l’entretien peut être assuré par l’utilisateur.
• Ne pas tenir la sonde de l'autre côté du protège-doigt entre le corps et l'arbre de sonde lors
d'une prise de mesure sur un conducteur sous tension dangereuse. De plus, ne pas laisser la
moindre tension dangereuse s'approcher davantage du protège-doigt que le marqueur de
sécurité indiqué sur l'arbre de sonde. Voir le schéma ci-contre.
• Avant d'attacher le joint torique à un câble nu sous tension dangereuse ou de l'en détacher,
s'assurer que le conducteur n'est pas alimenté.
• Ne pas utiliser la sonde quand elle est humide ou dans une situation de condensation. Ne
pas mouiller l'appareil lors de son nettoyage.
AVERTISSEMENTS et PRÉCAUTIONS
Sécurité
o
C. Ne pas exposer
Adaptateur d’alimentation CA
L'adaptateur/chargeur fourni est doté d'une cote universelle de tension d’entrée de 100-240 V CA,
50/60 Hz. Il s'agit d'un appareil de classe 2 (à double isolation), entièrement approuvé selon les
normes EN 60950-1 (2001) et UL 60950 (listing UL E245390).
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classés CAT III.
CAT I de cette sonde est de 2500 V.
Symboles
Les symboles suivants figurent sur la sonde de courant ainsi que dans le présent manuel.
AVERTISSEMENT – Risque d'électrocution
ATTENTION – se reporter à la documentation jointe (le présent manuel).
L'appareil peut être endommagé si ces précautions ne sont pas prises en compte.
Ne pas appliquer sur ou retirer des conducteurs sous tension dangereux.
Application sur des conducteurs sous tension dangereux acceptable.
Protégé dans son intégralité par isolation double ou isolation renforcée.
Courant alternatif (CA)
Courant continu (CC)
CAT II
CAT I
Indique les mesures de catégorie II ; la cote de tension maximum à la terre pour les
mesures de CAT II est habituellement indiquée avec le symbole. Les mesures de
catégorie II s'appliquent aux mesures effectuées sur des circuits directement
branchés sur une alimentation secteur basse tension, par exemple des
équipements et des appareils portables. La CAT II n'inclut pas de mesures sur des
circuits du niveau de distribution, par ex. des tableaux de distribution, des
disjoncteurs, des barres omnibus, etc., ou des installations industrielles, tous étant
Indique les mesures de catégorie I ; la cote de tension maximum à la terre pour les
mesures de CAT I est habituellement indiquée avec le symbole. Les mesures de
catégorie I s'appliquent aux mesures effectuées sur des circuits qui ne sont pas
directement branchés sur une alimentation secteur basse tension. Cette catégorie
inclut des circuits secondaires séparés des circuits d'alimentation secteur par un
transformateur et des circuits provenant de l'alimentation secteur pour lesquels des
mesures ont été prises afin de limiter les surtensions transitoires à un niveau plus
faible approprié. La surtension transitoire maximum autorisée pour la cote de 600 V
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