Aim TTi BS407 INSTRUCTION MANUAL [ml]

BS407

Precision Milli/Micro Ohmmeter

INSTRUCTION MANUAL

Table of Contents

Introduction 2
Specification 3
Safety 4
Installation 5
Connections 6
Front Panel Controls 7
Operation 8
Maintenance 11

Instructions en Francais

Sécurité 12
Installation 13
Connexions 14
Commandes du panneau frontal 15
Fonctionnement 16
Maintenance 20

Bedienungsanleitung auf Deutsch

Sicherheit 21
Installation 22
Anschlüsse 23
Frontplatten-Bedienungseinrichtungen 24
Betrieb 25
Reparatur 29

Istruzioni in Italiano

Sicurezza 30
Installazione 31
Collegamenti 32
Controlli sul pannello frontale 33
Operazione 34
Manutenzione 37

Instrucciones en Español

Seguridad 38
Instalación 39
Conexiones 40
Controles del panel frontal 41
Funcionamiento 42
Mantenimiento 46

1

Introduction

The BS407 is fully optimised for accurat e m easur ement of low resistances with a best resolution
of 1µΩ. It has applications beyond the t es t ing of components such as measuring t he r esistance
of motor or transformer windings, the properties of materials, the thickness of plates, the security
of pipework joints or wiring installations and many others.

It uses a Direct Current technique to measure true r es istance, r at her t han the resistive
component of impedance which is shown by AC excited RLC bridges. The test current for each
range has been carefully chosen to minimise heating of the sample under test while being
sufficient to minimise the effects of thermal emf and noise. This gives much greater accuracy at
low resistances than can be obtained from the very low test currents used by general purpose
high resolution multimeters. The low-noise low-drift bipolar amplifiers em ployed need much less
noise filtering than alternative chopper stabilised technolog ies r esult ing in faster settling t o t he
correct reading.

The BS407 uses a four terminal measur em ent s ystem and is supplied with a set of high quality
Kelvin clip leads. For speed and convenience front panel switches are provided for current
diversion (allowing in-situ zero adjustment) and current reversal ( for identifying thermal emf
effects). An indicator lamp confirms correct flow of t he m easur ing current thus preventing
spurious results from being recor ded.

The BS407 has eight push-button selected decade m easur em ent ranges from 1999µ Ω up to

19.99kΩ. A front panel operated ‘clamp’ switch is available to limit the maximum voltage across
the unknown to 20mV. This is a requirement for the measur em ent of switch contact resistances
to international standards. With a lowest range of 1999µΩ the BS407 can resolve 1µΩ. Precision
analogue circuitry ensures high measurement acc ur acy of up to 0.1% of reading ± 1 digit.

The BS407 is a fully portable instrument which operates fr om NiMH rechargeable bat t eries.
Stabilised internal operating conditions ensure that readings do not vary with the state of the
battery charge. The battery charger is built into the instrument and can be operated while
measurements continue.

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50 mA

1 mV

0.1% reading + 0.2% range

50 µA

10 mV

0.1% reading + 0.1% range

Source emf:

18 mV (±2mV) with clamp active, < 6 V otherwise.

Compliance:

> 0.5 V on 1999µΩ range, > 1. 0 V on all other r anges.

sources up to 50 V.

Battery:

4 internal non-removable Ni-MH cells. Low battery indication in display.

measurement on lowest range.

Power:

110V–120V or 220V–240V AC (internal setting) ±10%, 50/60 Hz, 20VA max.

Recharge time:

Nominally 12 hours with instrument not in use.

Operating Range:

Indoor use +5ºC to +40ºC, 20% to 80% RH, up t o 2000m , Pollution Degree 1.

Storage Range:

−40ºC to +50ºC.

http://www.aimtti.com/support (ser ial no. needed) .

Size and Weight:

220 mm (w) x 102 mm (h) x 235 mm (d), 1.5 kg.

Accessories:

Supplied with Kelvin clip leads.

Ranges and Accuracy

The 3½ digit display has a 1999 count full scale. Eight ranges are provided:

Specification

Accuracies apply for a calibration interval of 1 year at 23º ± 5º C af t er 5 minutes warm-up, with the
instrument and test connections in thermal equilibrium and the zero correctly set.
Temperature coefficient outside the stated range is < ±45 ppm/ºC.

Facilities

Set zero by front panel control with switch to divert test current from unknown.
Test current polarity reversal f or thermal emf detection.
Front panel lamp indicates correct force cir cuit m eas ur em ent c onditions.
20mV source emf clamp to limit open circ uit voltage acros s t he unknown to 20mV maximum for

"dry circuit" testing of switch and relay contacts. ( Not available on 2kΩ and 20kΩ ranges.)

Range Resolution

1999 µΩ 1 µΩ

19.99 mΩ 10 µΩ

199.9 mΩ 100 µΩ
1999 mΩ 1 mΩ

19.99 Ω 10 mΩ

199.9 Ω 100 mΩ
1999 Ω 1 Ω

19.99 kΩ 10 Ω

Test Current F.S. voltage Accuracy

250 mA 500 µV 0.1% reading + 0.4% range

10 mA 2 mV 0.1% reading + 0.1% range

5 mA 10 mV 0.1% reading + 0.1% range

500 µA 10 mV 0. 1% r eading + 0.1% range

10 µA 100 mV 0.1% reading + 0.1% range
10 µA 200 mV 0.1% reading + 0.2% range

Built-in battery charger allows instrument operation while re-charging.

Measurement circuit

Protection: The meter is pr ot ected against the back-emf of its own test current f r om any

General

Operating time: Typically > 150 hours with no test current flowing, > 8 hours cont inuous

Safety and EMC: Complies with EN61010-1 & EN61326-1.

inductance and against accidental short-term connect ion to exter nal voltage

For details, request the EU Declaration of Conformity for this instrum ent via

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incorrect operation may damage the instr um ent.

Safety

This instrument is Safety Class I accor ding to IEC classification and has been designed to meet
the requirements of EN61010−1 (Safety Requirements for Electrical Eq uipm ent for
Measurement, Control and Laboratory Use). It is an Ins tallation Category II instrument intended
for operation from a nor m al single phase supply.

This instrument has been tested in accordanc e with EN61010−1 and has been supplied in a safe
condition. This instruction manual contains some information and warnings which have to be
followed by the user to ensure safe operation and to r etain the inst r um ent in a safe condition.

This instrument has been designed f or 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 bet ween +5° and −10°C without degradation of its safet y. Do not
operate while condensation is present.

Use of this instrument in a manner not spec ified by these instructions may impair the safety
protection provided. Do not operate the instrum ent outside its rat ed supply voltages or
environmental range.

WARNING! THIS INSTRUMENT MUST BE EARTHED

Any interruption of the mains earth conduct or inside or outside t he inst r um ent will make the
instrument dangerous. Int ent ional inter ruption is prohibited. The protective action must not be
negated by the use of an extension cord without a protective conductor.

When the instrument is connected to its supply, terminals may be live and opening the covers or
removal of parts (except those to which access can be gained by hand) is likely to expose live
parts. The apparatus shall be disconnected from all voltage sources before it is opened for any
adjustment, replacement, m aint enance or r epair.

Any adjustment, maintenance and repair of the opened instrument under voltage shall be
avoided as far as possible and, if inevitable, shall be carried out only by a skilled person who is
aware of the hazard involved.

If the instrument is clearly defective, has been subject to mechanical damage, excessive
moisture or chemical corrosion the safety protection may be impaired and the apparatus should
be withdrawn from use and returned for checking and repair.

The instrument contains both non-reset t ing and self-resetting t her m al fuses which are not
replaceable by the user. The short-circuiting of these protective devices is prohibited.

The instrument contains Nickel Metal Hydride batteries. Do not open, puncture, incinerate or
short circuit these cells. These batteries must be disposed of in accordance with local regulations
and should be removed from the instrument before its final disposal.

Do not wet the instrument when cleaning it.
The following symbols are used on the instrument and in this m anual:−

Caution −refer to t he acc om panying documentation,

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alternating current.

Mains Operating Voltage

The operating voltage of the instr um ent is shown on the rear panel. Should it be necessary to
change the operating voltage from 230V to 115V or vice-versa, proceed as follows:

1. Disconnect the instrument from all voltage sources.

2. Remove the screws which hold the case upper to the case lower and lift off.

3. Disconnect the 3 way cable from the power supply PCB, remove the six screws and lift
the PCB from the case. The Power Supply PCB has an insulator attached to its underside
to ensure that the batteries are not accidentally short circuited. The centre pin of the
retaining rivets can be carefully pushed out allowing them to be re-used. Replace the
insulator immediately after servicing is complete.

4. Fit the soldered links f or the required operating voltage:­ For 230V fit only LK2

For 115V fit LK1 and LK3 and not LK2
These links may be either tinned copper wire or zero-ohm resist or s.

5. Refit t h e power supply PCB to the case lower and reconnect t he 3 way cable.

Installation

6. Refit the case upper tak ing care not to overtighten the scr ews.

7. To comply with safet y standard requirements the operating voltage mark ed on t he r ear

Fuses

There are no user replaceable fuses in the inst r ument.

Mains Lead

Connect the instrument to the AC supply using the mains lead provided. Should a mains plug be
required for a differ ent m ains out let soc ket, a suitably rated and approved mains lead set should
be used which is fitted with the required wall plug and an IEC60320 C13 connector for t he
instrument end. To determine t he m inimum current rating of t he lead-set for the intended AC
supply, refer to the power rating inf ormation on the equipment or in the Specification.

Any interruption of the mains earth conduct or inside or outside t he inst r um ent will make the
instrument dangerous. Int ent ional inter ruption is prohibited.

panel must be changed to clearly show the new voltage setting.

WARNING! THIS INSTRUMENT MUST BE EARTHED

5

Plug

Connection

All red

Sense +

Red with grey collar

Force +

All black

Sense –

Black with grey collar

Force –

Input Term inals

Connections are provided on the front panel for standard 4-terminal resistance measurements.
The test current f lows between the term inals m ar ked FORCE + and – and the voltage across t he
unknown resistance is measured between the terminals mark ed SENSE + and –. To obtain
correct readings the entire m easur ement circuit should be connected only to the resistance being
measured.

The instrument is supplied with a Kelvin lead set consisting of two special crocodile clips
connected to four 4mm plug s. The upper and lower jaws of each c r ocodile clip are not elect rically
connected: the grey jaws are used as the f or c e t er m inals and t he colour ed jaws (red and black)
as the sense terminals. The grey jaws are connected to the plugs which have a grey collar.

Connect these leads to the instrument as follows:

Connections

The instrument can be used with any other 4 terminal connection ar r angement as required by the
physical size of the resistance being measured.

The measurement circuit is not grounded (even when the battery is charging) but for the safety of
the operator the connections should be within ±30 volts from eart h. It is permissible for the c ircuit
to be externally connected to earth at one point only.

The maximum voltage emitted from t he instrument is 6V DC.

Protection

When measur ing the resistance of large iron-cor ed induct or s the test current builds a magnetic
field within the core. When this current is removed a back-em f is generated as the f ield
collapses. Take care when disconnecting the test leads from inductors not to touch the terminals
as the back-emf can g ive a noticeable electr ic shoc k. It is better to depres s t he Set Zer o s witch
and allow the instrument to absorb the stored energ y before disconnecting the inductor.

Protection circuits within the instrument ensure that it will not be damag ed by the back-emf of its
own test current from any inductance.

It is not intended that any external voltage be applied to the input terminals. However, there are
circuits designed to protect the instrum ent against brief accidental connections. In the case of
more severe misuse fusible resistors pr ot ect the internal circuits. These resistors are not
replaceable by the user.

6

Front Panel Controls

The following paragraphs give a brief descr ipt ion of the controls. Fuller details of the operation of
the instrument are given in later sections.

Operate

The Operate switch connects the measurement c irc uits t o t he bat tery; it does not control the
battery charger which operates whenever the unit is connected to the supply mains.

Set Zero

Depressing the Set Zero switch diverts the test current away from the Force terminals so there is
no voltage drop across the resistance being measured. The reading can then be set to zero
taking account of the eff ec t of external thermal emfs.

20mV Clamp

Depressing the 20mV Clamp switch limits the open circuit voltage of the force terminals to 20mV.
This is used when measuring the contact resistance of switches or r elays as this low voltage
does not break down oxide films.

Polarity

Depressing the Polarity switch reverses the direction of t he t est current through the unknown. If
there are no thermal emfs in t he m eas ur em ent circuit the two readings should be the same (apart
from the minus sign). If a thermal emf is pr esent it will add to one reading and subtract from the
other; the true resistance value is obtained by taking the numerical average.

Range switches

The legend above the range switches shows the display units (µΩ, mΩ, Ω or kΩ). The nominal
measurement current is shown below the switches for reference.

Charge lamp (red)

The Charge lamp will light while the unit is connected to the mains supply which causes the
battery to be charged. The unit should be disconnected from the supply when the battery is fully
charged.

Force On lamp (green)

The Force On lamp lights when the test current is flowing correctly. If the 20mV clamp is in use
the lamp will only light when the external voltage drop is less than the clamp threshold.

Display

The 3½ digit display shows the measurement result. I t should only be taken as valid when the
Force On lamp is lit and the BAT indicator is off. When the resistance is too large for the range
selected (or the sense leads are open circuit) the oversc ale indication consists of a 1 and three
blank digits. A negative sign will show when reverse polarity readings are being taken. The zero
setting is signed; the display will alternate between –000 and +000 at true zero.

The signal BAT in the lower left corner of the display shows when the battery is nearly
discharged. At this point readings are still accurate, but there is no further indication when the
battery voltage falls to the point that err or s arise; therefore when the BAT indication is displayed
the charger should be connected to the supply.

7

Switching On

Switch on the instrument using the Operate switch on the front panel. If ther e are no digits shown
in the display then the batteries may be completely discharged. Connect the unit t o the supply
mains; the Charge lamp should light t o show that char ging is taking place. If display operation
does not resume after a few minutes charging time the unit may be fault y; switch off , disc onnect
from the supply and seek service.

Battery Charging

When the unit is connected to the supply mains the red Charge lamp will be illuminated and the
battery will be charging. Resistance measurements may continue while charging with some small
reduction in accuracy because of the temperature rise within the unit. Charging norm ally takes
about 12 hours but if the 2000µΩ range is used the 250mA test current considerably reduces the
charging current and it will take longer t o fully charge the battery. A taper charge characteristic is
employed to quickly raise the charge level of a completely discharged battery and reduce the
current once fully charged; nevertheless, t he unit s hould not be lef t on continuous float charge as
this will reduce battery life.

The Ni-MH cells used do not suffer from any memory eff ect and are not harmed by either
complete discharge or partial re-charge.

While the unit is not in use t he batteries will self-discharge. This effect is g r eatly increased at
higher temperatures. I f the unit has been stored for so long that the batteries have become
completely discharged it may require two or three charge–discharge cycles for full capacity to be
restored.

The batteries are not replaceable by the user. If the capacity becomes noticeably low then the
unit should be sent to a qualified service facility f or the batteries to be replaced. The cells must
be handled and disposed of in accordance with local safety and environmental requirements.

Operation

Principles of Operation

This instrument measures resistance using the ratiometric method: a t es t current is passed
through both a precise internal reference resistance and the unknown resistance. The magnitude
of the test current is c hosen acc or ding to the range selected; it is a com pr om ise bet ween
sensitivity to noise and thermal emfs and minimising self-heating of the unknown. The voltages
developed across the two resistances are compared using a ratiometric Analogue to Digital
converter which calculates the result for the display.

The accuracy of this method depends on the acc ur acy of the reference resistor s and on sensing
the exact voltage drop across the unknown, not on the magnitude of the test curr ent . The two
main sources of error are voltage drops in the connect ions and t hermal emfs.

The problem of voltage drops is overcome by the 4 terminal connection. The curr ent flows in the
force leads and the instrument can t oler at e any voltage drop in these leads up t o its com pliance
limit. There is no voltage drop in the sense leads because of the very high input impedance of the
voltage measuring circuit in the unit. The resistance is measured between the physical points
where the sense leads connect to the unknown.

An emf is produced at any junction between dissimilar metals. The magnitude of this emf
depends on the materials and the temperatur e. I n any closed circuit which starts and ends on the
same metal (as in the sockets of t he instrument) there will be a equal number of junctions
between dissimilar metals. If all the pairs of junct ions ar e at t he s am e t em perature then the net
emf around the circuit is zero, but if there are temperature differences then the sum of t he em fs
is not zero - this difference is the thermal em f of the circuit. I t is of ten of the order of a few tens of
microvolts which is sufficient to influence the reading on low resistance ranges.

8

The instrument cannot distinguish bet ween this emf and the voltage drop across the test sam ple
caused by the measuring current. However if the direction of the test current is r eversed t hen t he
thermal emf will add to one reading and subtract from the other; the t r ue r es istance can be
calculated as the average of the two readings. This is the purpos e of the Polarity switch.

The most effective way to remove thermal emf s is by rem oving t he t em perature differences; take
care when connecting samples not to hold the connections points in the f ingers - do not touch
plug contacts when connecting the leads. Wait until ther m al equilibrium is established - it can
take many minutes for the eff ect of even the most brief contact with the fingers to dissipate.

The effect of ther m al em fs could also be eliminated by the use of an AC measurement technique
but this results in measuring the resistive component of impedance (including the effect of any
core losses etc.) rather than t he true resistance value obtained by the DC method used in this
instrument.

Setting Zero

To set the zero reading it is nec essary that the force current is flowing (so the reference
resistance is experiencing normal conditions) and that there is no voltage between the sense
terminals. The ZERO ADJUST control can then be set for a reading of zero to com pensate for
the internal offset voltages of t he inst r ument.

The most direct way to do this is to use one cable to connect FO RCE + to FORCE – and a
second cable to join SENSE + to SENSE –, select t he r ange required and use the ZERO
ADJUST control to obtain a reading of zero. Note that this r eading is s ig ned: the exact zero is at
the point where the minus sign in the display appears on alternate readings. These cables are
then removed and the test sample connected as required. This method zeros the internal offsets
within the instrument.

The zero adjustment can also be used to remove the effect of small external thermal emfs from
the measurement. Connect the tes t cables to the unknown ready to take a measurement and
select the required range. Depr ess t he Set Zer o button and set the reading to zero. Release t he
Set Zero button and allow the reading to settle at t he r es istance value. This is the most
convenient method in normal use.

Note that the zero cannot be set with the sense terminals open circ uit .

Connecting the Unknown Resistance

The Kelvin clips supplied with the instrument make the force and sense connections on opposite
sides of the conductor. This suits wire-ended components and long thin objects.

When measur ing low resistance physically large samples, separate wires and clips may be
needed for the two sets of connections which must be made in a way that reflects the required
measurement. The sense terminals should be connected to t he s am ple at the exact points
between which the resistance is to be measured; the force t er m inals should be connect ed to the
sample outside the sense terminals. They should be sufficiently far from the sense connections
to allow for the region where the current spreads out ac r oss t he cr os s -section of the sample.

When measur ing c om ponents t he t es t connec t ions should m at c h t he applicat ion connect ions as
closely as possible; when measuring the properties of mat er ial samples, consistency of
connection is the most important thing. This may requir e t he c onst ruction of a suitable jig.

The green Force On lamp lights when the test cur r ent flowing through the unknown produces a
voltage drop within the compliance specification of the instrum ent. A valid reading can then be
obtained provided that the sense connections are properly made (if t hey are not then the display
will normally show the overrange indication). Note that when measuring very large inductances
(such as high voltage transformers) there may be a delay before the lamp lights as it tak es s om e
time for the test cur r ent to rise to the full value (the rat e of rise of the current depends on t he
inductance and the source emf of t he inst r um ent). Similarly it takes time for t he cur r ent to reverse
when the Polarity selection is switched.

It is very important when attaching connections to avoid touching any metallic part of the circuit,
because the heat conducted from t he fingers will generate thermal emfs that take a significant
time to decay.

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Tak ing the Reading

After setting zero, release the Set Zer o switch and allow the reading t o set tle at the resistance
value. Note this reading and depress the Polarity switch; ideally (if there are no external t her mal
emfs) this reading will be the same as the first. If it is not , take the numerical average of the two
(ignore the sign); this value is the tr ue r es istance. Not e t hat if the sample is not in thermal
equilibrium the reading will be changing because of bot h t her mal emfs and the temperatur e
coefficient of the unknown.

It is possible to check the results by depressing t he Set Zer o but t on, noting the zero reading and
then computing the two differences between this value and the reading of each polarity (taking
the signs into account). These two values should agree within a digit; if they do not, then the
thermal emfs are changing too rapidly for a reliable measurement to be m ade.

Contact Resistance Measurements

The contacts of relays, switches etc. are often c overed by oxides or corrosion pr oducts. I f the
voltage in the circuit being switched is not high enough to break down this insulating film the
contact resistance measured will be much higher than that measured in a high power conditions.
In order to obtain a reading that reflects the operation of the component in t hes e “ dr y circuit”
conditions it is necessary to ensure that the test equipment does not subject the sam ple t o a high
open circuit voltage. International standards define t he “ dr y circuit ” m easurement voltage as
being not more than 20mV.

This instrument contains a suitable clamp circuit activated by the front panel 20mV Clamp push
button. This places an inter nal elect r onic shunt across the force ter m inals and cont r ols t he
resistance of this circuit to maintain a voltage of 18m V ( ± 2m V) bet ween these t er m inals. When
the contact being measured closes, its resistance must be s ufficiently low for the voltage drop
across it (at the measuring cur rent of the range selected) to be less than the clamp voltage. The
internal shunt then switches off, the gr een For c e O n lamp lights and the correct resistance
reading is displayed.

Note that battery drain is higher when the clamp is engag ed as t he m eas ur em ent c ur r ent is
always flowing, either through the internal clamp or the exter nal contact .

The 20mV clamp facility does not operate with the 2k Ω or 20kΩ r anges as the maximum
measurement voltage on these ranges is g r eat er than 20mV.

Applications

To measure the tem per at ure rise of the windings of a transformer or motor first measure the
resistance with the item cold. Then disconnect the meter and operate t he device f or the required
period of time. Disconnect all supplies and re-connect t he m eter and measure the winding
resistance in the hot condition. Knowing the temperature coefficient of the winding material these
two resistance readings can be used to calculate the temperat ur e change.

Measurement Notes

If the reading drifts cont inuously this may indicate either a change in a thermal emf caused by a
change in temperature or a real chang e in t he r es istance of the item being measured. I f the
sample is physically small this may be caused by the heating effect of the tes t current. Using a
higher range reduces the test c ur r ent but also reduces the measurement resolution.

Random fluctuations in the reading of more than a digit may indicate poor connections t o t he
sample under test, particularly the sense leads. It can also be caus ed by mag netic fields
intersecting the test circuit ; m ove the leads t o keep them close together and away from any
transformers or m otors.

If the three readings (zero, normal and reverse polarity) do not correlate then eit her t her e is a
poor connection, or a thermal emf is changing rapidly or the actual value being measured is
changing rapidly.

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Semiconductor junctions will appear open circuit in both directions because the m easur ement
voltage of this instrument is too small to c ause any noticeable conduction.

The Manufacturers or their ag ents overseas will provide a repair service for any unit developing a
fault. Where owners wish to undertake their own maintenance work, this should only be done by
skilled personnel in conjunction with the service manual which may be purchased directly from
the Manufacturers or their agents overseas.

Cleaning

If the instrument r equires 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, NEVER
ALLOW WATER TO GET INSIDE THE CASE. TO AVOID DAMAGE TO THE CASE NEVER
CLEAN WITH SOLVENTS.

Calibration

To ensure that the acc ur acy of the instrument remains within specification t he c alibrat ion m ust be
checked (and if necessary adjust ed) annually. This requires acc ess t o acc ur at ely known standard
resistors; the instrument is adjusted to obtain the correct readings from these resistors. This
instrument has independent calibration for each r ange.

Maintenance

Fuses

The transformer pr imary is protected by a non-resetting therm al fuse inside the windings. It can
only be replaced by fitting a new transformer.

The battery charge and discharge c irc uits are pr ot ec t ed by self-resetting devices. If it is
suspected that one of these has t r ipped, disconnect the unit from the mains supply, switch it off
and wait ten minutes. It is likely that any such tripping indicates an int er nal fault and the unit
should be serviced by a competent repair facility.

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incorrecte risque d'endommager l'appareil.

Sécurité

Cet instrument est de classe de sécurité 1 conforme à la classification IEC et il a été conçu pour
satisfaire aux exigences de la norme EN61010-1 (Exigences de sécurité pour les équipements
électriques de mesure, de contrôle et d' ut ilisation en labor at oir e) . I l s'agit d'un instrument de
Catégorie II d'installation devant être exploité depuis une alimentation monophasée standard.

Cet instrument a été testé conformément à la norme EN61010-1 et il a été fourni en tout état de
sécurité. Ce manuel d'instructions contient des informations et des avertissements qui doivent
être suivis par l'utilisateur afin d'assurer un fonctionnement et un état en toute sécurit é.

Cet instrument a été conçu pour être ut ilisé en intér ieur, en environnement de pollution de
deuxième degré (Pollution degree 2) à des plages de tem pér atures de 5°C à 40°C, et à des taux
d'humidité compris entre 20% et 80% ( sans c ondensation). Il peut être soumis de temps à autr e
à des températures comprises entr e + 5° C et –10° C sans dégradation de sa sécurité. Ne pas
l'utiliser en conditions de condensation.

Toute utilisation de cet instr um ent de m anièr e non spéc ifiée par ces instructions risque d'aff ecter
sa protection de sécurité. Ne pas utiliser l'instrument hors des plages de tension d'alimentation
nominale recommandées ni hors de ses tolérances d'environnement.

AVERTISSEMENT ! CET INSTRUMENT DOIT ETRE RELIE A LA TERRE

Toute interruption du conducteur de la terre du secteur à l'intérieur ou à l' extér ieur de l'instrument
rendra l'instrument dangereux. I l est absolum ent int er dit de pr iver intent ionnellement l' inst rument
de son branchement à la terre. La sécurité de l' inst r um ent ne doit pas être annulée par
l'utilisation de rallonge sans conducteur de protect ion.

Lorsque l'instrument est r elié au sect eur, il est possible que les bornes soient sous tension :
l'ouverture des couvercles ou la dépose de pièces (à l'exception des pièces accessibles
manuellement) risque de mettr e à découvert des pièces s ous tension. L'instrument doit être
débranché du secteur et de toute source d' alimentationavant t out r églage, remplacement,
travaux d'entretien ou de réparations.

Eviter dans la mesure du possible d'effectuer des rég lages, travaux de réparations ou d'entretien
lorsque l'instrument ouvert est br anc hé au secteur. Si cela s'avère toutefois indispensable, seul
un technicien compétent connaissant les risques enc our us doit effectuer ce genre de travaux.

S'il est évident que l'instrument est défectueux, qu'il a été soumis à des dégâts mécaniques, à
une humidité excessive ou à une corrosion chimique, la protection de sécurité est affaiblie :
l'instrument doit être retir é de l'exploitation et renvoyé vérifications et de r éparat ions.

Cet instrument contient à la fois des fusibles thermiques non rajustables et aut o-réglables ne
pouvant faire l'objet d'un remplacem ent par l'utilisateur. Il est strictement int er dit de c our t -circuiter
ces fusibles de protection.

Cet instrument contient des piles au nickel-hydrure de métal. Ne pas ouvrir, percer, incinérer ni
court-circuiter ces piles. Ces piles doivent être j et ées conformément aux lois et règlements
locaux en vigueur et doivent être retirées de l'instrument avant d' en disposer.

Ne jamais humidifier l'instrument lors du net t oyag e.
Les symboles suivants se trouvent sur l'instrument, ainsi que dans ce m anuel.

ATTENTION - se référer à la documentation ci-joint e; toute utilisation

Courant alternatif (c.a. )

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Tens ion de fonctionnement secteur

La tension de fonctionnement de l'instrum ent est indiquée à l'arrière. S'il est nécessair e de la
modifier de 230V à 115V ou vice-versa, procéder comme suit :

1. Débrancher l'instrument de toutes les sources d'alimentation.

2. Retirer les vis qui maintiennent le couvercle supérieur et s oulever ce couvercle.

3. Débrancher le câble trois voies de la carte à circuits imprimés d'alimentation, retirer les 6
vis et soulever la carte du boîtier. La carte d'alimentation porte un isolateur sur sa face
inférieure pour éviter tout court -circuit accidentel de la batterie. La goupille centrale des
rivets de fixation peut être soigneusement poussée vers l’extérieur pour r éut iliser les
rivets. Remettre l’isolateur en place immédiatement après la r évision.

4. Établir les connexions selon la tension appropriée:­ 230V: LK2 uniquement

115V: LK1 et LK3 et non LK2
Il peut s'agir de fil de cuivre étamé ou de résistances zéro ohm.

5. Rebrancher la carte d'alimentation dans le boîtier et rebr ancher le câble trois voies.

Installation

6. Remettre le couvercle en place en prenant soin de ne pas trop ser r er les vis.

7. Pour satisfaire aux exigences en matièr e de s écur it é, la t ension de fonctionnement
indiquée à l'arrière de l'instrument doit êt re modifiée pour indiquer la nouvelle tension
opérationnelle.

Fusibles

Cet instrument ne contient aucun f usible rem plaçable par l'ut ilisateur.

Cordon d'alimentation

Branchez cet instrument sur l’alimentation secteur en utilisant le câble d’alimentation fourni. Si la
prise murale requiert l’utilisation d’un câble d’alimentation différent, un c âble appr opr ié et
approuvé, qui possède une fiche correspondante à la pr ise m ur ale et un connec t eur d’inst r um ent
IEC60320 C13, doit être utilisé. Pour vérifier la tension nominale du câble d’alimentation en
fonction de la prise secteur, consultez les informations de puissance nominale sur l’équipement
ou dans Caractérstiques.

AVERTISSEMENT ! CET INSTRUMENT DOIT ÊTRE RELIÉ À LA TERRE

Toute interruption du conducteur de terre secteur à l'intérieur ou à l' extérieur de l' inst r um ent
rendra l'instrument dangereux. Toute interruption intentionnelle est absolument inter dite.

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Prise

Branchement

Toute rouge

Sense +

Rouge à col gris

Force +

Toute noire

Sense –

Noire à col gris

Force –

Bornes d'entrée

Le panneau frontal permet de brancher les appareils de mesure standard à 4 bornes. Le cour ant
de test circule entre les bornes FORCE + (force +) et - et la tension sur la résistance inconnue
est mesurée entre les bornes SENSE + ( dét ec t ion + ) et -. Pour obtenir les valeurs correctes, le
circuit de mesure tout entier ne doit êtr e branché qu'à la résistance mesurée.

Cet instrument est four ni avec un jeu de câbles Kelvin consistant en deux prises crocodile
spéciales, branchées à quatre prises de 4 m m . Les mâchoires supérieure et inférieur e de
chaque prise crocodile ne sont pas connectées mécaniquement : les mâchoires grises ser vent
de bornes de forces et les mâchoires de couleur (rouge et noire) servent de bornes de détection.
Les mâchoires grises se branchent aux prises à col gr is.

Branchez les câbles à l'instrument comme suit :

Connexions

Cet instrument peut être utilisé avec n'importe quelle combinaison à 4 bornes, requise par la
taille physique de la résistance mesurée.

Le circuit de mesure n'est pas relié à la terre (m êm e lors que la batterie se recharge) mais, pour
la sécurité de l'utilisateur, les connexions devraient se trouver à ±30 volts de la terre. Il est permis
de relier le circuit à la terre par voie externe et en un point uniquement.

La tension maximale émise par l'instrument est de 6V CC.

Protection

Lorsque vous mesurez la résistance de gros inducteurs à noyau de f er, le courant de test établit
un champ magnétique dans le noyau. Une fois ce cour ant supprimé, une force électromot r ice en
retour est générée par la chute du champ magnétique. Nous conseillons la prudence aux
utilisateurs lorsqu'ils débranchent les câbles des induct eur s : ne pas toucher les bornes - la
f.é.m. peut donner un choc électrique notable. Il est préférable d' appuyer sur le bout on Set Zer o
(remise à zéro) et permettre à l' inst r um ent d'absorber l'énergie emmagasinée, avant de
débrancher l'inducteur.

Les circuits de protection intégrés à l'instr um ent préviennent tout dommage éventuel pouvant
être causé par le retour de f.é.m . de son propre courant de test.

Il n'est pas prévu d'appliquer quelque tension externe que ce soit aux bornes en entrée.
L'instrument contient, tout efois, des circuits conçus pour le protéger des branchements
accidentels de courte durée. Dans l'éventualité d'une utilisation err onée plus grave, des
résistances à fusible protègent les circuits inter nes. Ces résistances ne peuvent être remplacées
par l'utilisateur.

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