QuadTech 1657 RLC Digibridge User manual

1657 RLC Digibridge®
Instruction Manual
Foun 1657-0120-07/B1
®QuadTech, Inc., 1992
5 Clock Tower Place, 210 East
Maynard, Massachusetts, U.S.A. 01754
January, 1997
Tel. [phone]
800-253-1230 (Sales)
800-253-1230 (Service)
Fax. [phone]
The material in this manual is for informational purposes only and is subject to change, without notice.
QuadTech assumes no responsibility for any error or for consequential damages that may result from the
misinterpretation of any procedures in this publication.
Contents
Instruction Manual Changes
Specifications
Warranty
Introduction -Section 1
Installation -Section 2
Operation -Section 3
Theory -Section 4
Service and Maintenance -Section 5
Parts Lists and Diagrams -Section 6
~ Product will be marked with this symbol (ISO#3684) when it is necessary for the user to refer
to the instruction manual in order to prevent injury or equipment damage.

These two supplementary pages contain information of improvements or modifications not
documented in the current manual. All references to GenRad in the manual now apply to
QuadTech, Inc.
Page -Specifications (Power & Mechanical)
Powershould be90 -250V AC, 50 -60 Hz. Voltage switching is automatic and no
longer selected by rear panel switch. 60 Watts maximum.
Weightshould be 10 lbs. (4.5kg)net, 15 lbs. (6.8 kg)shipping.
Environmentreads, Altitude < 2000m, Installation Category 1, Pollution Degree 1
Page - Table of Contents (Parts Listand Diagrams -Section 6)
Powersupply board(1657-4720) layout and diagram (page 6-13) replaced by Power
supply assembly part number 700011 (no diagrams, repair by module exchange)
Page 1-4 -Figure 1-2, Rear Panel Controls and Connectors
Rear view should show new power supply assembly (PN 700011) without line-voltage
switch.
Page 1-4 -Table 1-2, Rear Panel Connectors and Controls
RefNo. 2R -&Fuse is 6/10A, 250V, 3AG Type, Slow Blow. Replace only with
the same type and rating. To replace, remove fuse drawer by pressing up on release tab.
RefNo. 3R -Line-voltage switch has been deleted, power input isfrom 90 -250V AC
Page1-4 -Table 1-3, Accessories
A quantity of two spare fuses are supplied, 6/10A, 250V, 3AG Type, Slow Blow
(QuadTech part number 5330-1100)
Page 2-1 -Safety Inspection
Before operating the instrument inspect the powerinlet module on the rear oftheunit to
ensure thatthe properly rated fuse is in place, otherwise damageto unit ispossible. Fuse is
6/l0A, 250V,3AG Type, Slow Blow.
The 1657 is shipped with a standard U.S. power cord, QuadTech PN 4200-0300 (with Belden
SPH-386 socket or equivalent, and 3 wire plug confonning to IEC 320) or an approved
international cord set. Make sure the instrument is only used with these or other approved
international cord sets, which ensures the instrument is provided with connection to protective
earth ground.
In all installations the instrument should be positioned with consideration for ample air flow to the
side and rear panel ventilation holes. An open space around the instrument of at least 3 inches
(75mm) is recommend. The surrounding environment should be free from excessive dust to
prevent contatnination of electronic circuits.

Page 2-1 -Power-Line Connection
Powerline switch for 115V or 230Voperation has been removed, switching is
automatic for voltages between 90 -250V AC.
Page 2-2 -Figure 2-2
Figure 2-2 does not apply. Only certified line cords which comply with IEC 227 or
IEC 245 should be used.
Page 3-2 -Paragraph 3.1 Basic Procedure, step a
Powerline switch for 115V or 230Voperation has been removed, switching is
automatic.
Page 5-1 -Paragraph 5.2, Instrument Return
Contacts for QuadTech are:Sales 800-253-1230
Service 800-253-1230
Technical Assistance978-461-2100
Page 5-2 & Page 5-3 -Caution Note
Powerline switch for 115V or 230Voperation has been removed, switching is
automatic.
Page 5-7 -& Paragraph 5.6.1 & Figure 5-3, Disassembly
PowerSupply Assembly shown has been replaced by Power Supply Assembly PN
700011.
Page 5-10 -Instrument Cleaning Instructions
Monthly (more orless depending on usage) the built-in testfixture should be cleaned
with a soft brush and isopropyl alcohol. Avoid getting excess alcohol on instrument paint
surfaces, otherwise damage to the finish can result. For additional instrument cleaning
instructions refer to paragraph 5.7.1 (Care of the Test Fixture) and paragraph 5.7,2 (Care of the
Display Panel).
PowerSupply Assembly shown in Figure 5-8 has been replaced by Power Supply
Assembly PN 700011.
Page 5-12 - Paragraph 5.8.2, Power Supply
Trouble Analysis procedure does not apply to new Power Supply Assembly P/N 700011.
Page 6-2 - Figure 6-2, Rear View
Rear view should show new power supply (PN 700011) without line-voltage switch
Page 6-3 - Mechanical Parts List, Rear
Items 1 - 4 (power connector, fuse extractor post, line voltage switch & cover) deleted on new assembly
Page 6-12 & Page 6-13 - Parts and Diagrams
Power Supply Board and Parts List shown, PN 1657-4720 has been replaced by
Power Supply Assembly, PN 700011. The 700011 Assembly must be repaired by module exchange.

Environment:TEMPERATURE:0°to 50°C operating,-40°to +75°C
storage. HUMIDITY: 0 to 85% R.H., operating.
Supplied: Power cord, axial-lead adaptors, instruction manual.
Power: 90 to 125 or 180 to 250 V, 50 to 60 Hz. Voltage selected
by rear-panel switch. 25 W maximum.
Mechanical: Bench mounting. DIMENSIONS: (wxhxd): 375x112x343 mm
(14.8x4.4x13.5 in.).WEIGHT:5.6 kg(12.3lb)net,l0kg (22 lb)shipping.
Patent applied for.
Accuracy: ForR, L,and C:+/- 0.2%ofreadinginbasic ranges, ifquadrature
componentissmall(D< 0.1, Q> 10, etc).See table. D accuracy:+/- .001 in basic
ranges, forD < 0.1 (otherwise, see table). Qaccuracy:+/-.01 in basic ranges,forQ< 1
(otherwise, see table).
Measurement Mode:Measures Rseries or parallel; Land Q series or parallel; C
and D series or parallel. All measurement modes are pushbutton selectable.
Displays: LED-typenumerical display withautomaticallypositioneddecimal points
and illuminationofunits.For R LC,fivedigits (99999) and simultaneously for DQ,
four digits (9999).
Measurement Speed: Greater than 3 measurements per second.
/
Test frequencies:Pushbuttonselectionbetween2. Accuracyrepanel
legends:+2%,-.01%.Actualfrequencies:for1657-9700, 1020.0 Hz+/- .01% (panel
legend "1 kHz")and 120.00 Hz+/- .01%;
for 1657.9800,1000.0 and 100.00 Hz+/- .01%.
Applied Voltage: 0.3 V rms maximum.
Ranges:Pushbuttonselectionwithautomaticfront-panelguidance. Three basic ranges
(best accuracy, see table) of 2 decades each, for each parameter. Automatic extensions
to min and max, as tabulated.

SERVICE POLICY
QuadTech policy is to maintain product repair capability for a period of five (5) years after original
shipment and to make this capability available at the then prevailing schedule of charges.

Table of Contents

1.1 PURPOSE1-1
1.2GENERAL DESCRIPTION 1-1
1.3 CONTROLS, INDICATORS, ANDCONNECTORS1-1
1.4 ACCESSORIES1-1
1.1 PURPOSE.in keepingwith thelong-lifecircuitryinside. Glass-epoxy
The1657 Digibridgedigital impedancemeterembodiescircuit boards interconnect and supporthigh-quality com
useofa microprocessorand otherLSIcircuitryto ponents to assureyearsofdependability.
provide excellent performance at lowcost. Adaptability to anycommon ac powerline is assured by
Afewclearlylabeledpushbuttonsand the versatiletheremovable power cord and the convenient line-voltage
built-intest fixturemake this instrument a modelforcon- switch. Safety is enhancedby the fused,isolatingpower
venience. Measurement results areclearly shown with dec- transformerand the3-wirepowerconnection. A compre
imal points and units,whichareautomaticallypresented to hensivefunctionaldescriptionis giveninTheory, Section 4
assurecorrectness. Display resolution is5 digits forR, C,Electrical and physical characteristics arelistedin Specifi
and L (4forDorQ)andthebasic accuracy is 0.2%.cations at thefront ofthis manual,dimensions in Installa
Long-termaccuracy and reliability areassured by the tion,Section 2. Controlsaredescribed below,and their use
measurementsystem.Itmakes these accurate analog inOperation, Section3.
measurements overmany decadesofimpedance without a
singlecalibrationor "trimming" adjustment(not evenin 1.3CONTROLS,INDICATORS,AND CONNECTORS.
original manufacture)..
Thebuilt-in test fixture,with a pair ofplug-in adaptors,Figure:-1 showsthe front panelconrolsandindicators.
receivesany common component part(axial-lead orradial-Table1-1identifiesthemwith descriptions andfunctions.
lead) so easily thatinsertion of the DUT isaone-hand Similarily, Figure 1-2 shows the rear panel and Table 1-2 identifies
t
.
.I
.I
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ent
ifi
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escr
ib
es t
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e rearpane
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contro
l
s an
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connec
operation.True4-terminal connectionsare made automat
.ically. Extender cables and other accessories are available and describes the rear panel controls and connectors.
formeasurements at adistance fromthe Digibridge.
1.4 ACCESSORIES.
Gen Rad makes several accessories that enhance the use
1.2 GENERAL DESCRIPTION. fulness of this instrument. Two extender cables facilitate
Convenience is enhanced by the arrangement of test making connections to those devices and impedance stan
fixture on the front ledge, with push buttons farther for- dards that do not readily fit the built-in test fixture. A
wardanddisplaybehind.The displaypanel isinclined andremote testfixture (used withBNC adaptorand cable
recessed to enhance visbility of digital readouts and mode assembly) provides convenience and relatively easy main
indicators. Theseindicatorsserve toinformand guidethetenance,andsaves wearon the built-intestfixture. All of
operatoras he operatesthesimplecontrols.these test-fixtureaccessoriesprovide fortrue 4-terminal
The instrument stands on a table or bench top. The connections (and guard) to the device being measured,
sturdy metal cabinet is attractively and durably finished, without appreciable reduction in measurement accuracy.
Other useful accessories are offered, such as standards for
checking the performance of the Digibridge. Refer to
Table 1 -3 and Section 5.
INTRODUCTION 1-1

1-2 INTRODUCTION

INTRODUCTION 1-3

1-4 INTRODUCTION

2.1 UNPACKING AND INSPECTION.
If the shipping carton is damaged, ask that the carrier's
agent be present when the instrument is unpacked. Inspect the instrument
for damage (scratches, dents, broken parts, etc.). If the instrument is
damaged or fails to meet specifications, notify the carrier and the nearest
GenRad field
office. (See list at back of this manual). Retain the shipping carton and the
padding material for the carrier's inspection.
2.2 DIMENSIONS Figure2-1.
The instrument is supplied in the bench configuration,
i.e., in a cabinet with resilient feet for placement on a table. The overall
dimensions are given in the figure.
2.3POWER-liNE CONNECTION.
The power transformer primary windings can be switched, by means of
the line voltage switch on the rear panel, to ac. commodate ac line voltages
in either of 2 ranges, as labeled, at a frequency of 50 or 60 Hz, nominal.
Using a small screwdriver, set this switch to match the measured voltage of
your power line.
I f your I ine voltage is in the lower range, connect the 3-wire power
cable(P/N4200-9625)to the powerconnectorontherear panel(Figure1-2)
and then to the power line.
The instrument is fitted with a power connector that is in conformance
with the International Electrotechnical Commission publication 320. The 3
flat contacts are surrounded by a cylindrical plastic shroud that reduces the
possibility of electrical shock whenever the power cord is being unplugged
from the instrument. In addition, the center ground pin is longer, which
means that it mates first and disconnects last, for user protection. This panel
connector is a standard 3-pin grounding-type receptacle, the design of which
has been accepted world wide for electronic instru. mentation. The connector
is rated for 250 V at 6 A. The receptacle accepts power cords fitted with the
Belden type SPH-386 connector.
The associated power cord for use with that receptacle, for line voltages
up to125 V,is GenRadpart no. 4200-9625.
It is a 210-cm(7ft),3-wire, 18-gagecablewith connectorbodiesmolded
integrally with the jacket. The connector at the power-line end is a stackable
hammerhead design that conforms to the "Standard for Grounding Type
Attachment Plug Caps and Receptacles," ANSI C73. 11-1966, which
specifies limits of 125 V and 15 A. This power cord is
listed by UnderwritersLaboratories, Inc., for125V,10 A.
If the fuse must be replaced, be sure to use a "slow blow" fuse of the
current and voltage ratings shown on the rear panel, regardless of the line
voltage.
INSTAllATION 2-1

If your line voltage is in the higher range selectable by the line voltage
switch, use a power cord of the proper rating (250 V, 15 A) that mates
with both instrument and
your receptacle. It is possible to replace the "hammerhead" connector on the
power cord that is supplied with a suitable connector. Be sure to use one
that is approved for 250 V, 15 A. A typical configuration is shown in Figure
2-2.
2.4 LINE-VOLTAGEREGUlATION
The accuracy of measurements accomplished with precision electronic
test equipment operated from ac line
sources can often be seriously degraded by fluctuations in primary input
power.line-voltagevariations of+/-15%arecommonlyencountered, even
in laboratory environments.
Although most modern electronic instruments incorporate some degree of
regulation, possible power.source problems should be considered for
every instrumentation setup. The use of line-voltage regulators between
powerlinesand the
test equipment is recommended as the only sure way to rule out the effects
on measurement data of variations in line voltage.
2.5TEST-FIXTURECONNECTIONS.
2.5.1 TestFixtureon the Digibridge.
Because an unusually versatile test fixture is provided on the front shelf
of the instrument, no test-fixture connection is generally required. Simply
plug the device to be measured (DUT) into the test fixture, with or without
its adaptors. For details, refer to paragraphs 3.1, 3.2. Accessories can be
attached to extend and adapt the test fixture, as described below.
2.5.2 Remote TestFixture.
Connection of the DUT at a remote test fixture requires proper adaptors
and cable connections from the Digibridge. Obtain the following
accessories. (See Table 1-3.)
BNC Adaptor 1689-9601
BNC CableAssembly 1689-9602,orequivalent
Remote Test Fixture 1689-9600, or equivalent
handler or special fixture.
This remote test fixture functions like the one supplied on the
Digibridge. True "Kelvin" connections are made at the points of contact
withthe DUT leads.Install as
follows:
a. Remove any adaptors, if present, from the test
fixture.
b. Plug the BNC adaptor into the basic test fixture with the BNC
connectors facing forward. lock the connection with the 2 captive thumb
screws. (The screws must be
seated to complete the ground connection.)
c. Connect the cable assembly to the adaptor on the Digibridge and to
the remote test fixture as indicated in Table 2-1.
NOTE
User provided cables and/or remote test
fixtures can be used, particularly if the
DUT isto be handledautomatically.
See paragraph 3.7 for comments on cable
and fixture capacitance.
2.5.3 The 1657-9600 ExtenderCable(Banana Plugs).
The accessory extender cable 1657-9600 is available to connect to
DUTs that are multiterminal, physically large, or otherwise unsuited for
the built-in test fixture. This cable is particularly convenient for connecting
multiterminal components with binding posts that accommodate banana
plugs. Use the following procedure to install the extender cable on the
instrument.
a. Remove the adaptors, if present, from the test
fix tu re.
b. Plug the single-connector end of the extender cable into the
Digibridge test fixture so that its blades enter both slots and the cable lies
away from the display panel. lock the connector with the two captive
thumb screws.
c. Note the color coding of the five banana plugs. Be sure that the
"low"terminals(both potential and current) connecttoone end of the
DUT and the "high"terminals tothe other end. Connectguard toashield if
any,but not toeither end of the DUT.
2-2 INSTAllATION

P-(potential, low) = Black/white
I-(current, low) = Black
P+(potential,high) = Red/white
I+(current, high) =Red
Guard = Black/green
2.5.4 The 1688-9600 ExtenderCable
("Type 874" Connectors).
The accessory extender cable 1688-9600 can be used to connect a
DUT that is multiterminai, physically large, or otherwise unsuited for the
built-in test fixture. This
low-capacitance cable is used, for example, to connect type-874
connected impedance standards or a special
test fixture. Make connections as follows:
a. Remove the adaptors, if present, from the test fixture.
b. Plug the single-connector end of the extender cable into the
Digibridge test fixture so that its blades enter both slots and the cable lies
away from the display panel. Lock the connector with the two captive
thumb screws.
c. Using the branched end of the cable, connect to the DUT with
careful attention to the following color code.
The cable tips are type 874 coaxial connectors, which
mate with a broad line of components and adaptors.
Notice that the 2 wires with red must connect to the same end of the
DUT, through a coaxial tee if the DUT is a 2-terminal device; the 2
wires labeled with black, connect to the other end, similarly. Connect
the outer (shield) contacts to the shield or case of the DUT only if it
is isolated from both ends of the DUT.
EXTENDER CABLE COLOR CODE
RED AND RED: 1+, current drive to
"high" end of DUT.
RED AND WHITE: P+, potential connection
to same.
BLACK AND BLACK' I-, current return at
DUT "low".
BLACK AND WHITE: P-, potential
connection to same.
OUTER CONTACTS: G, guard connection
to shield or case.
2.6 EXTERNALBIAS.Figure2-3.
WARNING
To minimize electrical shock hazard,limit
biasto 30V.
Bias voltage ispresentatconnectors,test
fixtures and on capacitors under test.
Capacitors remain charged aftermeasurement.
Do NOT leave instrument unattended withbias
applied.
Full bias voltage appears on test leads, bias-voltagesource terminals,
and on the leads of the component being measured. Capacitors that have
been charged are dangerous until properly discharged; the user must follow
safe procedures to assure discharge. For safety, all personnel operating the
instrument with bias must be aware of the hazards, follow safe procedures,
and never leave the equipment unattended with bias voltage applied.
2.6.1 Basic Bias Connections.
In order to measure a capacitor with dc bias voltage
applied, connect an external voltage source, as follows:
a. Attach the remote test fixture or an extender cable as described in
paragraph 2.5. Observe the color coding explained there.
INSTALLATION 2-3

b. Connect a suitable bias voltage source (see below)
in series with the 1+ connection, basically as shown in
the diagram, with the following details.
With the Remote Test Fixture. Disconnect the red coded BNC cable end
from the remote test fixture and connect one end of plain BNC cable there
instead.
Connectthe redcodedBNC cable end tothe negative terminal of the bias
voltage source. Connect the remaining free end of the plain BNC cable to
the positive terminal of the bias voltage source. Connect the DUT to
the test fixture in the usual way.
With 1657-9600 Extender Cable (Banana Plugs). Connect the red
banana plug to the negative terminal
of the bias voltage source. Connect a suitable banana
plug patch cord to the positive terminal. We designate
the freeend ofthis patch cordas I++, as shown in the
diagram.
With 1688-9600 Extender Cable
("Type 874 Connectors").
Connect the "red and red" cable to the negative terminal of the bias voltage
source. Connect a suitable type-874 patch cable to the positive terminal.
We designate the
freeend ofthis patchcableas I++, as shown in thediagram.
c. If either of the extender cables (not the remote test fixture) is used,
connect the DUT as follows. If capacitance is large (range 1), make 2
connectionsto each capacitorterminal (Kelvin connections). That is, I-and
P-to capacitornegativeterminal;P+and I++ to capacitorpositive
terminal.
If the capacitance is smaller (range 2 or 3) the banana plugs can be
stacked ora teeusedwith type-874 connectors
anda single connection madetoeach capacitor terminal: I-/P-tothe
negative terminal, P+/I++ to the positive.
To make 3-terminal (or 5-terminal) measurements, also connect guard
(see paragraph 2.5) to the guard terminal, shield, case, or ground of the
capacitor, provided that this is insulated from the 2 main terminals of the
capacitor. Do not connect guard to the case of a capacitor if the case is one
of its 2 main terminals.
2.6.2 Bias VoltageSource Description
The bias voltage source must satisfy several criteria:
1. Supply the desired terminal voltage (dc)
2. Serve as source for charging current.
3. Serve as source and sink for the measuring currents
(ac), which are 45, 0.45, and .0045 mA, peak, for measurements on ranges
1, 2, and 3, respectively.
4. Present a low,linear terminal impedance (< < 10ohms)
at measuring frequency.
If the bias voltage source is a regulated power supply
with the usual characteristic that it functions properly only as a source, not
a sink, then the following test setup is
recommended. Connect across the power supply a bleeder resistor that
draws dc current at least as great as the peak measuring current (item 3
above). In parallel with the bleeder, connect a 100-pF capacitor. (If the
power supply has exceptionally good transient response, the capacitor is
not necessary.)
No single bleeder resistor will suffice for all bias conditions, so it may
be necessary to switch among several. Each resistance must be small
enough to keep the power supply regulator current unidirectional (as
mentioned above) for the smallest bias voltage in its range of usefulness.
Also the resistance and dissipation capacity must be large enough so that
neither the power supply is overloaded nor the resistor itself damaged for
the highest bias voltage in its range of application.
NOTE
For convenience, a suitable active current sink
can be used in lieu of bleeder resistors.
A discharge circuit is also required. (Do not depend on the above-
mentioned bleeder resistor.) A dual discharge circuit is recommended.
Connect a clip lead with a 10-Q resistor in series and another plain clip lead
to the I-/Pjunction. Provide the loose ends of these with insulated alligator
clips for use when completing the discharge path across the DUT. For a
recommended procedure, refer to para 3.6.
I f the measurement program warrants the expense of a test fixture for
biased-capacitor measurements, its function should be equivalent to that of
the circuit described above. It should be equipped with convenient
switching to remove the bias source, discharge through 10 Q, and finally to
short out the capacitor after measurement. For automated test setups, it is
also feasible to precharge the capacitors before they are attached to the test
fixture and to discharge them after they have been removed.
CAUTION
To avoid damage to the instrument, limit the bias voltage to 30 V,
maximum, in any precharging
bias supply, used as mentioned above.
2.7 ENVIRONMENT.
The Digibridge can be operated in nearly any environment that is
comfortable for the operator. Keep the instrument and all connections to
thepartsunder test awayfrom
electromagnetic fieldsthat mayinterfere withmeasurements.
Refertothe Specificationsatthe frontof this manual fortemperature
and humidity tolerances. To safeguard the instrument during storage or
shipment, use protective packaging. Refer to Section 5.
2-4 INSTAllATION

OPERATION 3-1

3.1 BASIC PROCEDURE.Figure3-1.
For initial familiarization, follow this procedure care
fully. For details, refer to later paragraphs in Operation.
a. Before connecting the power cord, slide the linevoltage switch (rear
panel) to the position that corresponds to your power-line voltage. Power must
be nominally either 50 or 60 Hz ac, either 120 or 220 V. (Refer to
specifications at front of this manual.) The 1657-9700 can be run on 50 Hz but
with some loss of accuracy for 120-Hz measurements in high range
extensions. Similarly, the 1657-9800, if run
on60-Hzpower,experiencessomeextraneous noisein100Hz
measurements in high range extensions.
If the fuse must be replaced, be sure to use a "slow
blow" fuse of the rating shown on the rear panel.
b. Connect a typical device, whose impedance is to be
measured, as follows. (This device under test is denoted DUT.)
NOTE
Clean the leads of the DUT if they are notice
ably dirty, even though the test-fixture contacts
will usually bite through a film of wax to pro
vide adequate connections.
Radial-lead DUT:Insertthe leadsintothe test.fixture
slots as shown in the photograph, Figure 1-1. For details of wire size and
spacing limits, refer to para 3.2.
Axial-lead DUT:Install the test-fixture adaptors, supplied,one in
each slot of the test fixture, as shown in the accompanying figure. Slide
the adaptors together or apart
so the body of the DUT will fit easily between them. Press the DUT down
so that the leads enter the slots in the adaptors as far as they go easily. For
details of wire size and DUT size limits, refer to para 3.2.
NOTE
To remove each adaptor, lift with a gentle tilt
left or right. For a DUT with very short leads
it is important to orient each adaptor so its internal contacts
(which are off center) are close
to the DUT.
Other DUTs, Remote Connections, and Bias.
For connections via extender cables and remote
test fixtures, refer to the installation instructions of paragraph 2.5. For
connection of bias voltage and operating procedures with bias, refer to
paragraphs 2.6 and 3.6. For convenience, the typical color coding used in
extender cables is repeated below.
Red:I+,current connection to "high"end of DUT.,
Red & white: P+potential connection to same.
Black: I-, current connection to low endofDUT. .
Black & white: P-, potential connection to same
Black & Green: G, guard connection to shield or case (if isolated
from the preceding terminals). Do not-connect G to the case of a capacitor
if the case serves as (or is connected to) one of its 2 main terminals.
3-2 OPERATION
Notice that the 2red tipsmust connect tothe same end of the DUT. The
terminals with white bands are potential connections; with no bands, current
terminals.
c. Set.the pushbuttons according to the desired measure
ment, as follows:
Power. Depress thePOWER buttonso that itstays inthedepressed
position. (To turn the instrument off, push and release this button so that it
remains in the released position.)
Function. For resistance, depress R. For inductance, depress L/Q. For
capacitance, depress C/D. Be sure that one of these buttons is in the
depressed position.
Frequency. Formeasurementat1kHz, pushand release the
FREQUENCY button until the 1-kHz light comes on. For 120 (100) Hz, push
the same button so that the 120-Hz (100.Hz) light comes on.
Parallel or Series. For series equivalent circuit, push and release the
PARALLEL/SERIESbutton untilthe SERIESlightcomeson. For parallel
equivalent circuit, push this button so that the PARALLEL light comes on.
(The choice is significant for lossy capacitors or inductors, not for lowloss
reactive components or non-reactive resistors.) For further explanation, refer
to para 3.5.
Range. Depress the middle (RANGE-2) button first and watch the
ADJUST RANGE lights. If the right-pointing arrow is lighted, depress
RANGE button at the right. If the left-pointing arrow is lighted, depress
RANGEbuttonat theleft. Whenneitherarrowis lighted,therangeyouhave
selected is correct. (Be surc that one of the RANGE buttons is in the
depressed position.) Additional comments on range choices are below.
d. Read the measurement on the main displays. The
R LC display is the principal measurement, complete with decimal point and
units,which areindicated by the light spotbehindMΩ,kΩ,Ω,H,mH, nF,
oruF.*TheDQdisplayis Dif theC/D FUNCTIONbutton is in,Qif the
L/Q button is in.
e. After any change in DUT or measurement conditions, before looking
at the displays, notice the ,ADJUST RANGE
lights. Interpret them as follows:
Neither light. Correct range. (There are minor exceptions.)
LeftLight.Wrong range; trynext RANGE button toleft.
Right Light. Wrong range; try next RANGE button to
right.
Both Lights. Overrange or invalid display. If FUNCTION is correct
and RANGE is highest, the measurement is valid but because of an
overrange condition, the basic 0.2% accuracy cannot be guaranteed. (If you
switch to RANGE 2, one
of the lights will go out.) If both lights are lit on RANGE 2, either the
FUNCTION is inappropriate for the DUT or it is not properly connected.
For more details, refer to para 3.3.
*Ifthe extender cable isused. itmaybe necessarytocorrect forits
capacitance.

3.2CONNECTION OFTHE DUT.
3.2.1 The IntegralTestFixture.
The test fixture provided on the front ledge of the Digi
bridgeprovidesconvenient, reliable, guarded 4-terminal connectionto
any common radial-lead oraxial-lead component.
Ifthe slots ofyour test fixturehaverounded ends, the
slots accommodate wires ofany diameterfrom0.25mm(.01in., AWG
30) to 1 mm (.04 in., AWG 18), spaced from 6 to 98 mm apart (0.23 to 3.9
in.) or equivalent strip conductors. Each "radial" wire must be at least 1 cm
long
(0.4 in.). However, if the slots of your test fixture have square ends, they
will accommodate wires spaced as close as 4 mm (0.16 in.) and each
"radial" wire must be at least
4 mm (0.16 in.) long. The divider between the test slots contains a shield, at
guard potential, with its edges exposed. The adaptors accomm odate wi res
of any diameter up to 1.5 mm (.06 in., AWG 15). The body of the DUT that
will fit between these adaptors can be 80 mm long and 44 mm diameter
(3.1x1.7 in.) maximum. Each "axial" wire must be at least 3 mm long (0.12
in.).For radial-lead parts, remove each adaptor from the test fixture by a
gentle pull upward, made easier by bending the adaptor left or right (never
forward or back). For axial-lead parts, insert the adaptors, one in the left
slot and the other
in the right slot of the test fixture, by pushing vertically downward. They
can be slid left and right to match the length of DUT to be measured. Notice
that the contacts inside the adaptor are off center; be sure to orient the
adaptors so the contacts are close to the body of the DUT, especially if it
has short or fragile leads.
Insert the DUT so one lead makes connection on the
left side of the test fixture, the other lead on the right side. Insertion and
removal are smooth, easy operations and connections are reliable if leads
are clean and straight.
Be sure to remove any obvious dirt from leads before inserting them.
Be sure the contact pair inside each half of the test fixture is held open by a
single item ONLY, whether that is one lead of an axial-lead DUT or one
adaptor, to obtain true "Kelvin" connections.
3.2.2 Test FixtureAccessories.
An accessory extender cable or adaptor, cable, and remote test fixture,
as described in Table 1-3, is needed
to connect any DUT that is multiterminal, physically
large, or otherwise unsuited for the built-in testfixture.
Acable isneeded, forexample, toconnectimpedance standards, a
remotetestfixture, capacitorstobemeasured withbias,etc.For
connectionto the instrument, referto paragraph 2.5. For
measurementswithbias,
referto paragraphs2.6 and 3.6. Thecolorcode forthe branchedend
ofeach cableis given inparagraph 3.1.Tocorrect forcable
capacitance, referto paragraph3.7.
3.3FUNCTION AND RANGESELECTIONS.
3.3.1Function Pushbuttons.
The selection of the principal parameter to be measured is almost self-
explanatory. Depress the appropriate FUNCTIONbutton:R, L/Qor C/D to
measure resistance, inductance, or capacitance. The instrument will tolerate,
to some degree, a poor choice of function, but accuracy is thereby reduced.
The readout will indicate a completely wrong choice of function, as
explained below. Notice that the appearance of a device can be misleading.
(For example, a faulty inductor can be essentially capacitive or resistive;
a component part can be mislabeled or unlabeled.)
If both ADJUST RANGE lights are on, the RANGE 2 button is in, the
RLCdisplayisblank, andthe DUT isproperlyconnected, then the choice
offunction is probablywrong.Mostlikely, if the L/Qbutton isin,the DUT
iscapacitive; or ifthe C/D buttonis in,theDUTis inductive.
Observe the DQdisplayfor anindication of poor choiceof function
(though tolerable). Large D or small 0 may indicate that the "reactor" being
measured is practically a
resistor atthe measuring frequency.Ifthe C/D button is in and the D
reading is between 1 and 10 (or blank, as it will be for D> 10) it is
possible that the DUT is eno,ugh like a resistor to be measured best
withthe R button in.Similarly,ifthe L/Q button isin and the Qreading
is
between zero and 1, it is possible that the DUT is enough like a resistor to
be measured best with the R button in. Notice that when the R button is in,
the DOdisplayis alwaysblank. Onthe otherhand, any DorQdisplayis
valid, evenif the"wrong"functionhas beenselected. (The CorLdisplay
can be blank.)
If the R button is in (a resistor is being measured) the easy way to
determine whethertheDUTis reactiveis to trymaking C/D and L/Q
measurements.Ifyouobtain avalid CmeasurementwithD<1, the DUT is
capacitive. The smaller this D value, the less accurate the R measurement.
Similarly,ifyou obtain avalid LmeasurementwithQ >1, the DUT is
inductive. The largerthis Qvaluetheless accurate theRmeasurement. (See
para 3.4.)
3.3.2 RangePushbuttons.
Range selection is also nearly self-explanatory. Follow the ADJUST
RANGE lights. The left light means: "Push the next range button to the
left." The right-hand light
means: "Push the next range button to the right." Continue until both lights
go out. The instrument will usually display a measurement (at reduced
accuracy) even though the range is not optimum. The following details
about range are best
understoodwithreference to para3.4 (particu1arlythe RLCbasic accuracy
graph).
The RANGE buttons are placed in order of decreasing impedance, 3-2-
1.The "highest"range istherefore Range 1
for C/D;but it is Range 3for Rand L/Q.
OPERATION 3-3

Each basic range is slightly more than 2 decades wide, from an R LC
displayof01900, with an automatic decimal
point change between the decades, to19999. (Thesymbol 0represents
a blanked zero. Initial zeroes to left of the decimal point are always blanked
out oftheRLCdisplay.)Each ofthe3 rangesgoesbeyond its basic range,
with both upper and lower range extensions (shown by lighter lines in the
RLC basic accuracy graph). Several of these extensions are seldom used
becausetheyoverlap "basic" portions ofotherrangesandbecausethe
operator is alerted to this fact by an ADJUST RANGE light.
Each range includes 2 or 3 subranges, distinguished by the automatic
decimal-point shift. The operator does NOT control them. Subranges are
detailedin Table3-1.Notice, forexample,if you select RANGE1, C/D,1
kHz,thenthereare2 subranges:19uFand 999uF.Ifa seriesofmeasure-
ments is made with Cincreasing slowly above19uF, the automatic
subrange change takes place at 21. But with C decreasing, the change takes
place at 20. This hysteresis eliminates a possible cause of flickering of the
display.
The "low" extension of each range goes from 01900 down to 00000,
without any change in decimal point, but with reduced accuracy. The
number of digits in this display is always adequate for the specified
accuracy. Any measurement in the low extension of either Range 2 or the
highest range causes the appropriate ADJUST RANGE arrow to be lighted.
But there is no such light in the low extension of the lowest range (because
there is no lower range to select).
The "high" extension of each range is a factor of 5 (with 2 exceptions),
going from 19999 up to 99999, and finally to blank, without any change in
decimal point, but with reduced accuracy. Any measurement in the high
extension of either the lowest range or Range 2 causes the appropriate
ADJUST RANGE arrow to be lighted. However in
3-4 OPERATION
the high extension of the highest range, both ADJUST RANGE arrows are
lighted (to indicate a useful "overrange" condition) .
The high extension of the top range for Rand C only, at 120 Hz (100
Hz) only, is a factor of 50, going from 19999, with an automatic decimal-
point change, up to 99999, and finally to blank, with reduced accuracy.
(Both ADJUST RANGE arrows are lighted as described above.)
Aspecial casewarrants explanation. (This is aminorexception to the
basic procedureofpara3.1.)It is possible
forboth ADJUSTRANGE lights to be out and yet the RANGE and
FUNCTIONbuttons to be incorrectly set.
This condition result'sfromeitherfaulty connection to theDUTora
numerically small negative Lor C measurement. Sometimes a loose or dirty
connection tothe DUTcauses
anerratic RLCdisplay.Asmall negative Lor C (wrong function
selected) causes a zero display. In either case, check connections at the test
fixture and tryall 3 FUNCTIONStosee whichisappropriate, R, L/Q,or
C/D.
3.4 ACCURACY.
3.4.1 Graphs.Figures3-2, 3-3,and 3.4
The following accuracy graphs supplement the statement of accuracy in
the specifications, at the front of this manual.
Figure 3.2showsthat the RLCbasicaccuracyof 0.2% isrealized over
6 decadesofimpedance if the correct range
is selected(asindicated by the ADJUSTRANG E lights being out).
The reduction of accuracy is shown for all of the "low" and "high" range
extensions. This basic RLC accuracy is validonlyfor"pure"R. L, orC.
For the effect

Figure 3-2. R L C basic accuracy as a percent of reading. Heavy lines (solid and dotted) represent best
choice of range. Range 2 is dotted. Notice that Land C scales above graph are for 120 Hz (*equally valid for
100 Hz)and the 2 below graphare for1 kHz. The DQaccuracyfactor(right-hand scale) isthe multiplier
that, applied tothe DQBasic Accuracy, yields complete DQaccuracy, forrange extensionsas wellas the
basic ranges (whereRLCaccuracyis0.2%).
of quadratureimpedance, multiply eachbasic accuracyvalue bythe RLC
accuracy factor; see below.
Figure 3-3 shows the RLC accuracy factor, which depends on D or Q.
For example, suppose a capacitor measured at
1kHz hasC = 400 uFand D = 0.5. The R LCbasic accuracyis0.4%and
the R LC accuracy factor is 1.5. Therefore, the accuracy of the C
measurementis:+/-0.6%.Noticethat the
D or Qof a resistor (if significant)canbemeasured byselecting the C/D or
L/QFUNCTION.
Figure 3-4showsthe basic DQaccuracy,which issimple function of
DorQ.ForDread the lowerscaleand lowercurve.ForQread theupper
scale andupper curve. The basicDQaccuracyisvalid only if
measurementsare made on one of the 3 basic ranges (where RLC
accuracy
is best).Otherwise,multiplybasic DQaccuracy by the DQaccuracy
factor, shown onthe right ofthe "RLC basic accuracy"graph. In the
exampleofC = 400 uF,D= 0.5, thebasic D accuracyis 0.5%and the D
accuracyfactor is2. Therefore, the accuracyof the D measurement is:+/-1%
OPERATION 3-5

The logarithmic scales on these figures make it very easy to apply the
accuracy factors visually. For example, suppose a capacitor is being measured
on range 2, both ADJUST RANGE lights are out, and the D display' is about
1. Figure 3-3 shows that the C accuracy factor is about 1/3 of a decade on the
logarithmic scale. On Figure 3-2, find the heavy dotted line (the basic portion
of range 2) and point to the basic C accuracy (0.2%) at the left. Now apply the
C accuracy factor by moving the pointer up about 1/3 of a decade. The pointer
nowshowsthe corrected C accuracy,0.4%.
3.4.2 Insignificant Digits.
One or more of the digitsatthe right end of the R LCand/or DQdisplays
may be insignificant. This is particularly true at the upper extension of a
range. If there are more than one insignificant digits in a display, the least
significant is typically noisy. That is, it will appear to flicker at random over a
range of values and should be ignored.
Forexample, ifyou measure a 4-MΩresistor,the displaymightideally
be4.1234 MΩ;but the one or two final digitsmight bechangingatrandom.
Thisflickeringisentirelynormal.The specified accuracy(+/-0.4%)isthe key
to expected performance; in this example, the last 2 digits are insignificant
and the last digit is quite unnecessary. Typically, one would record this
measurementas4.12 +/-.02 MΩ.
3.5PARALLEL/SERIESAND FREQUENCY SELECTIONS.
3.5.1 General.
The value of the principal measurement (R, L, or C) of a certain DUT
depends on which of 2 equivalent circuits is chosen to represent it. (Many
impedance measuring instruments provide no choice in the matter, but this
one allows selection.) The more nearly "pure" the resistance or reactance, the
morenearly identical arethe"series" and "parallel"values. However, forD
or 0 near unity, the difference is substantial. Also, the principal measurement
often depends on measurement frequency. The more nearly "pure" the
resistance orreactance, the less is this dependence. However, forDorQ near
unity and/or for measuring frequency near the self-resonant frequency of the
DUT, this dependence
is quite substantial. We first give general rules for selection of measurement
parameters, then some of the theory.
3.5.2 Rules.
Specifications. The manufacturer or principal user of the DUT probably
specifies how to measure it. (Usually "series" is specified for C, L, and low
values of R.) Select "parallel" or: "series" and 1 kHz or 120 Hz (100 Hz)
according to the applicable specifications. If there are none known, be sure
to
3-6 OPERATION
specify with your results whether they are "parallel" or "series" and what the
measurement frequency was.
Resistors, belowabout1 kΩ:Series,120 Hz (100 Hz). Usuallythe
specifications call for dc resistance, so select a low test frequency to
minimize ac losses. Select "series" because the reactive component most
likely to be present in a low-resistance resistor is series inductance, which
has no effect on the measurement of series R. As a quick check on whether
the DUT is nearly pure resistance, make a separate "parallel" measurement.
Rp will be larger then Rs. If the difference is less then 1 %, then 0 is less
than 0.1, and the measured Rs is probably very close to the dc resistance.
Resistors,aboveabout 1 kΩ:Parallel, 120 Hz(100 Hz).As
explained above, select a low test frequency. Select "parallel" because the
reactive component most likely to be present in a high-resistance resistor is
shunt capacitance, which has no effect on the measurement of parallel R. As
a quick check on whether the DUT is nearly pure resistance, make a
separate "series" measurement. If the difference between Rp and Rs is less
than 1%, then D is greater than 10, and the measured Rp is probably very
close to the dc resistance.
Capacitors below 2 nF: Series, 1 kHz. Unless otherwise specified or for
special reasons, always select "series"
for capacitors and inductors. This has traditionally been standard practice.
Select a high measurement frequency for best accuracy.
Capacitorsabove 200 uF:Series,120Hz(100Hz).Select"series" for
the reasons given above. Select a low measurement frequency for best
accuracyand toenable measurementof capacitorslarger than1000uF.
Inductors below 2 mH: Series, 1 kHz. Select "series"
as explained above. Select a high measurement frequency for best accuracy.
Inductors above 200 H: Series, 120 Hz (100 Hz). Select "series" as
explained before. Select a low measurement frequency for best accuracy
and to enable measurement of inductors larger than 1000 H.
3.5.3 Seriesand ParallelParameters.Figure3-5.
An impedance that is neither a pure reactance nor a pure resistance can
be represented at any specific frequency by either a series or a parallel
combination of resistance and reactance. Keeping this concept in mind will
be valuable
in operation of the instrument and interpreting its measurements. The values
of resistance and reactance used in the equivalent circuit depend on whether
a series or parallel combination is used. The equivalent circuits are shown in
Figure 3-5. The relationships between the various circuit elements are as
follows.