BK Precision BK Precision 886 Manual

Models
885 & 886 LCR METER OPERATING
MANUAL
MANUAL DE INSTRUCCIÓNES
MEDIDOR LCR
Modelos 885 & 886
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Contents
1. INTRODUCTION ...............................................................
1.1 G
ENERAL
............................................................................. 1
MPEDANCE PARAMETERS
1.2 I
PECIFICATION
1.3 S
CCESSORIES
1.4 A
.................................................................... 6
.................................................................... 19
.................................................. 3
2. OPERATION ...................................................................... 21
2.1 P
HYSICAL DESCRIPTION
AKING MEASUREMENT
2.2 M
2.2.1 Battery Re placement ............................................................... 22
2.2.2 Battery Recharging/AC operation .......................................... 23
2.2.3 Open and Short Calibration ................................................... 24
2.2.4 Display Sp eed .......................................................................... 25
2.2.5 Relative Mode ......................................................................... 25
2.2.6 Range Hold.............................................................................. 25
2.2.7 DC Resistance Measurement .................................................. 26
2.2.8 AC Impedance Measurement .................................................. 26
2.2.9 Capacitance Measurement ..................................................... 26
2.2.10 Inductance Measurement ........................................................ 27
2.3 A
CCESSORY OPERATION
................................................... 21
................................................. 21
................................................... 28
4. APPLICATION .................................................................. 30
4.1 T
EST LEADS CONNECTION
PEN/SHORT COMPENSATION
4.2 O
ELECTING THE SERIES OR PARALLEL MODE
4.3 S
............................................... 30
.......................................... 35
.................. 37
5. LIMITED ONE-YEAR WARRANTY ........................... 37
6. SAFETY PRECAUTION ................................................. 42
1
1. Introduction
1.1 General
The B&K Precision Models 885 & 886 Synthesized In-Circuit LCR/ESR Meter is a high accuracy hand held portable test instrument used for measuring inductors, capacitors and resistors with a basic accuracy of 0.2%. It is the most adva nced handheld AC/DC impedance measurement instrument to date. The 885 or 886 can help engineers and student s to understand the character istic of electronics components as well as being an essential tool on any service bench.
The instrument is auto or manual ranging. Test frequencies of 100Hz, 120Hz, 1KHz 10KHz or 100KHz (886) may be selecte d on all applicable ranges. The test voltages of 50mVrms, 0.25Vrms, 1Vr ms or 1VDC (DCR only) may also be selected on all applicable ranges. The dual display feature permits simultaneous measurements.
Components can be measured in the series or parallel mode as desired; the more standard method is automatically selected first but can be overridden.
The Model 885 and 886 offers three useful modes for sorting components.
The highly versatile Mode ls can perf orm virtua lly all the functions of most bench type LCR bri dges. With a basic accuracy of 0.2%, this economical LCR meter may be adequately substituted for a
1
more expensive LCR bridge in many situations. The meter is powered from two AA Batteries and is supplie d with an AC to DC charging adapter and two AA Ni-Mh Rechargeable Batteries.
The instrument has applications in electronic engineering labs, production facilitie s, service shops, and schools. It can be used to check ESR v alues of capacito rs , sort values, select precision values, measure unmarked and unknown i nductors, capacit ors or resistor s, and to measure capacitance, inductance, or resistance of cables, switches, circuit boar d foils, etc.
The key features are as following:
Te st condition:
Frequency : 100Hz / 120Hz / 1KHz / 10KHz /
1
100KHz (886)
Level : 1Vrms / 0.25Vr ms / 50mVrms /
2. 1VDC (DCR only)
Measurement Parameters : Z, Ls, Lp , C s, C p , D C R ,
Basic Accu racy: 0.2%
Dual Liquid Crystal Display
Fast/Slow Measurement
Auto Range or Range Hold
Open/Short Calibrati on
Primary Parameters Display:
ESR, D, Q and
θ
Z : AC Impedance DCR : DC Resistance Ls : Serial Inductance Lp : Parallel Inductance
2
Cs : Serial Capacitance Cp : Parallel Capacitance
Second Parameter Display:
θ
: Phase Angle
ESR : Equivalence Serial Resistance D : Dissipati on Fact or Q : Quality Factor
Combinations of Display:
Serial Mode : Z –
θ
, Cs – D, Cs – Q, Cs – ESR, Ls –
D, Ls – Q, Ls – ESR
Parallel M od e : Cp – D, Cp – Q, Lp – D, Lp – Q
1.2 Impedanc e Parameters
Due to the different test ing signal s on t he impedance mea surement instrument, there are DC impedance and AC impedance. The common digital multi -meter can only measure the DC impedance, but the Model 885 can do both. It is a very important issue to understand the impedance parameters of the electronic component.
When we analysis the impedance by the impedance measurement plane (Figure 1.1). It can be visualized by the rea l element on the X-axis and the imaginary element on the y-axis. This impedance measuremen t plan e can also be seen as th e pola r coordin at es. Th e Z
θ
is the magnitude and the
is the phase of the impedance.
3
( )
( )
( )
( ) ( )
Ohm
Reactance
Resistance
Impedance
1
22
=
=
=
=
 
 
==
+==
=+=
S
S
s
s
s
sss
ss
X
R
Z
R
X
TanSinZX
XRZCosZR
ZjXRZ
θθ
θ
θ
s
X
s
R
( )
sX,RZ
s
Z
θ
Imaginary Axis
Real Axis
Figure 1.1
fCC
X
fLLX
C
L
πω
πω
2
11
2====
There are two different types of reactance: Inductive (X Capacitive (X
). It can be defined as f ollows:
C
L = Inductance (H)
Also, there are quality factor (Q) and the dissipation fac tor (D) that need to be discussed. For component, the quality fa ctor serve s as a measure of the reacta nce purity. In the re al world, t here is always
C = Capacitance (F) f = Frequency (Hz)
4
) and
L
pp
p
p
p
p
sss
s
s
s
RC
L
R
X
R
G
B
RCR
L
R
X
D
Q
ω
ω
ω
ω
δ
===
=
===
==
1
tan
11
some associated resistance that dissipates power, decreasing the amount of energy that can be rec overed. The quality fac tor can be defined as the ratio of the stored energy (reactance) and the dissipated energy (resistance). Q is generally used for inductors and D for capacito rs .
There are two types of the circuit mode. One is series mode, the other is parallel mode. See Fi gure 1.2 t o find out t he rela tion of t he series and parallel mode.
5
Parameter
Range
Z L
0.000 µH to 9999 H
C
0.000 pF to 9999 F
DCR
ESR
D
0.000 to 9999
Q
0.000 to 9999
ss
jXRZ +=
Real and imaginary components are Parallel
jB=1/jX
jBGY +=
jX
R
P
jX
1
P
R
1
Y +=
Real and imaginary components are serial
Rs jX
s
p
p
Figure 1.2
G=1/R
1.3 Specification
LCD Display Range:
0.000 Ω to 9999 MΩ
0.000 Ω to 9999 MΩ
0.000 Ω to 9999 Ω
6
p
p
|Zx|
20M ~
(Ω)
10M ~
(Ω)
1M ~
(Ω)
100K ~
(Ω)
10 ~ 1
(Ω)
1 ~ 0.1
(Ω)
DCR
100Hz
120Hz
1KHz
10KHz
100KHz
NA
2
1 Dx+
θ
-180.0 ° to 180.0 °
Accuracy (Ae):
Z Accuracy:
10M
1M
100K
10
Freq.
2% ±1
5% ±1
±
1 0.5% ±1 0.2% ±1 0.5% ±1 1% ±1
1%
2% ±1
(886)
5%±1
2%±1 0.4% ±1 2%±1 5%±1
Note : 1.The accuracy applies wh en th e test level is set to 1V rms.
2.Ae multiplies 1. 25 when the test level is set to 250mVrms.
3.Ae multiplies 1.50 when the test level is set to 50mVrms.
4.When measuring L and C, multiply Ae by Dx
0.1.
: Ae is not specified if th e test level is set to 50mV.
7
if the
79.57
pF
159.1
nF
1.591
nF
15.91
uF
159.1
uF
1591
mF
2% ± 1
1% ± 1
0.5% ± 1
0.2% ± 1
0.5% ± 1
1% ± 1
66.31
pF
132.6
nF
1.326
nF
13.26
uF
132.6
uF
1326
mF
2% ± 1
1% ± 1
0.5%
1
0.2%
1
0.5%
1
1% ± 1
7.957
pF
15.91
pF
159.1
nF
1.591
uF
15.91
uF
159.1
mF
2% ± 1
1% ± 1
0.5% ± 1
0.2% ± 1
0.5% ± 1
1% ± 1
0.795
pF
1.591
pF
15.91
pF
159.1
uF
1.591
uF
15.91
uF
5% ± 1
2% ± 1
0.5% ± 1
0.2% ± 1
0.5% ± 1
1% ± 1
NA
0.159
pF
1.591
pF
15.91
nF
159.1
uF
1.591
uF
C Accuracy :
100Hz
120Hz
159.1
132.6
pF
|
pF
|
pF
|
1.591
pF
|
1.326
nF
|
15.91
nF
|
13.26
nF
|
159.1
nF
|
132.6
uF
|
1591
uF
|
1326
uF
|
15.91
uF
|
13.26
1KHz
10KHz
100KHz
(886)
pF
|
15.91
pF
|
1.591
pF
|
159.1
pF
|
15.91
pF
|
1.591
±
pF
|
1.591
pF
|
159.1
pF
|
15.91
8
±
nF
|
15.91
pF
|
1.591
pF
|
159.1
±
uF
|
159.1
uF
|
15.91
nF
|
1.591
uF
|
1.591
uF
|
159.1
uF
|
15.91
NA
5% ± 1
2%± 1
0.4%
1
2%± 1
5% ± 1
31.83
KH
15.91
H
1591
H
159.1
mH
15.91
mH
1.591
uH
2% ± 1
1% ± 1
0.5% ± 1
0.2% ± 1
0.5% ± 1
1% ± 1
26.52
KH
13.26
H
1326
H
132.6
mH
13.26
mH
1.326
uH
2% ± 1
1% ± 1
0.5% ± 1
0.2% ± 1
0.5% ± 1
1% ± 1
31.83
KH
1.591
H
159.1
H
15.91
mH
1.591
uH
159.1
uH
2% ± 1
1% ± 1
0.5%
1
0.2%
1
0.5%
1
1% ± 1
318.3
H
159.1
H
15.91
H
1.591
uH
159.1
uH
15.91
uH
5% ± 1
2% ± 1
0.5%
0.2%
0.5%
1% ± 1
31.83
H
15.91
H
1.591
mH
159.1
uH
15.91
uH
1.591
uH
L Accuracy :
KH
100Hz
120Hz
1KHz
10KHz
15.91
KH
13.26
KH
1.591
159.1
H
KH
|
|
1591
159.1
KH
|
|
1326
132.6
KH
|
|
159.1
15.91
H
|
|
15.91
1.591
H
|
H
|
H
|
±
H
|
± 1
±
H
|
H
|
H
|
±
H
|
± 1
mH
1.591
mH
1.326
mH
159.1
±
uH
15.91
± 1
15.91
13.26
1.591
159.1
mH
|
|
159.1
mH
|
|
132.6
uH
|
|
15.91
uH
|
|
1.591
100KHz
(886)
H
|
15.91
H
|
1.591
H
|
159.1
9
mH
|
15.91
uH
|
1.591
uH
|
0.159
NA
5% ± 1
2%± 1
0.4%
1
2%± 1
5% ± 1
|Zx|
Freq.
20M ~
(Ω)
10M ~
(Ω)
1M ~
(Ω)
100K ~
(Ω)
10 ~ 1
(Ω)
1 ~ 0.1
(Ω)
±
0.020
±
0.010
±
0.005 ±0.002 ±0.005 ±0.010
±
0.050
±
0.020
100KHz
(886)
NA ±0.050
±
0.020 ±0.004 ±0.020 ±0.050
|Zx|
Freq.
20M ~
(Ω)
10M ~
(Ω)
1M ~
(Ω)
100K ~
(Ω)
10 ~ 1
(Ω)
1 ~ 0.1
(Ω)
±
1.046
±
0.523
±
0.261 ±0.105 ±0.261 ±0.523
±
2.615
±
1.046
100KHz
(886)
NA ±2.615
±
1.046 ±0.209 ±1.046 ±2.615
D Accuracy :
100Hz 120Hz
1KHz
10KHz
θ Accuracy :
100Hz 120Hz
1KHz
10KHz
10M
10M
1M
100K
1M
100K
10
±
10
10
CxfZx⋅
=
π
2
1
2
1 Dx+
=
=
=
1590
10100102
1
2
1
93
π
π
Cxf
Zx
Z Accuracy:
As shown in table 1.
C Accuracy:
= Ae of |Zx|
C
Ae
f : Test Frequency (Hz) Cx : Measured Capacitance Value (F)
|Zx| : Measured Impedance Value ( Accuracy applies when Dx (measured D value)
Ω
)
0.1
When Dx > 0.1, multiply C
Example: Test Condition: Frequency : 1KHz Level : 1Vrms Speed : Slow DUT : 100nF Then
Ae
by
11
LxfZx =π2
2
1 Dx+
100
Ae
XxESR
Ae
±=
Refer to the accuracy table, get C
L Accuracy:
= Ae of |Zx|
L
Ae
f : Test Frequency (Hz) Lx : Measured Inductance Value (H)
|Zx| : Measured Impedance Value ( Accuracy applies when Dx (measured D value)
=±0.2%
Ae
Ω
)
0.1
ESR Accuracy :
When Dx > 0.1, multiply L
Ae
by
Example: Test Condition: Frequency : 1KHz Level : 1Vrms Speed : Slow DUT : 1mH Then
2
π
=
π
LxfZx
33
283.610102
Refer to the accuracy table, get L
12
==
Ae
=±0.5%
Cxf
LxfXx
==
π
π
2
1
2
=
=
=
1590
10100102
1
2
1
93
π
π
Cxf
Zx
±=±= 18.3
100
Ae
Xx
ESR
Ae
ESR
= Ae of |Zx|
Ae
f : Test Frequency (Hz) Xx : Measured Reactance Value (
Lx : Measured Inductance Value (H) Cx : Measured Capacitance Value (F)
Accuracy applies when Dx (measured D value)
Example: Test Condition: Frequency : 1KHz Level : 1Vrms Speed : Slow DUT : 100nF Then
Refer to the accuracy table, get
=±0.2%,
C
Ae
Ω
)
0.1
D Accuracy:
13
100
Ae
D
Ae
±=
=
=
=
1590
10100102
1
2
1
93
π
π
Cxf
Zx
002.0
100
±=⋅±=
Ae
D
Ae
DeQx
DeQx
Ae
Q
±=
1
2
= Ae of |Zx|
D
Ae
Accuracy applies when Dx (measured D value) When Dx > 0.1, multiply Dx by (1+Dx)
Example: Test Condition: Frequency : 1KHz Level : 1Vrms Speed : Slow DUT : 100nF Then
Refer to the accuracy table, get
=±0.2%,
C
Ae
0.1
Q Accuracy:
14
005.0
100
±=⋅±=
Ae
De
1.01
= Ae of |Zx|
Q
Ae
Qx : Measured Quality Factor Value De : Relative D Accuracy Accuracy applies when
Example: Test Condition: Frequency : 1KHz Level : 1Vrms Speed : Slow DUT : 1mH Then
2
π
=
π
LxfZx
33
Refer to the accuracy table, get
=±0.5%,
L
Ae
If measured Qx = 20 Then
2
1
±=⋅
DeQx
DeQx
±=
Q
Ae
2
1<DeQx
==
283.610102
15
100
Ae
π
180
e =θ
=
=
=
1590
10100102
1
2
1
93
π
π
Cxf
Zx
deg115.0
100
2.0180
100
Ae180
Ae
±=
π
±=
π
±=θ
θ
Accuracy:
Example: Test Condition: Frequency : 1KHz Level : 1Vrms Speed : Slow DUT : 100nF Then
Refer to the accuracy table, get
=±0.2%,
Z
Ae
Testi ng Signal: Level Accuracy : ± 5% Frequency Accuracy : 0.1%
16
Output Impedance : 100Ω ± 5%
Measuring Speed: Fast : 4.5 meas. / sec. Slow : 2.5 meas. / sec.
General: Temperature : 0
°
C to 70°C (Operating)
-20 Relative Humidity : Up to 85%
Battery Type : 2 AA si ze Ni-Mh or Alkaline Battery Charge : Const ant current 150mA
Battery Operatin g Time : 2.5 Hours typical AC Operation : 110/220V AC, 60/50Hz with proper
Low Power Warning : under 2.2V Dimensions : 174mm x 86mm x 48mm (L x W x H)
Weight : 470g
Considerations
Test Fre quency. The test frequency is user selectable and can be changed. G ene rally, a 1 KHz test signal or higher is used to measure capacitors that are 0.01uF or smaller and a 120Hz test signal is used for capacitors that are 10uF or larger. T ypically a 1 kHz test signal or higher is used to measure induc tors that are used in audio and RF (radio frequency) circuits. This is because these components operate at higher frequencies and require that they be measure d at a hi gher frequency of 1 KHz. Generally, inductors below 2mH should be
°
C to 70°C (Storage)
approximately
adapter
6.9” x 3.4” x 1.9”
17
measured at 1 kHz and inductors above 200H should be measured at 120Hz.
It is best to check with the componen t manufacturers’ data sheet to determine the best test fre quency for the device.
Charged Capacitors Always discharge any capacitor prior to making a measurement since a charged ca pacitor may serious ly damage the meter.
Effect Of High D on Accuracy A low D (Dissipation Factor) reading is desirable. Electrolytic capacitor s inhe rently have a higher dissipation factor due to their normally high internal leakage characteristics. If the D (Dissipation Factor) is ex c es sive, the capacitanc e measurement accuracy may be degraded.
It is best to check with the componen t manufacturers’ data sheet to determine the desirabl e D val ue of a good component.
Measuring Capacitance of Cables, Switches or Other Parts Measuring the capacitance of coaxial cables is very useful in determining the actual length of the cable. Most manufacturer specifications list the amount of capacitance per foot of cable and therefore the length of the cable can be determined by measuring the capacitance of that cable.
For examp le: A manufa cturers , specificat ion calls out a certa in cable,
18
to have a capa citance of 10 pF per foot, After measuring the cable a capacitance reading of 1.000 nF is displayed. Dividing 1000pF (1.000 nF) by 10 pF per foot yields the length of the cable to be approximately 100 feet.
Even if the manufacturers’ specification is not known, the capacitance of a measured length of cable (such as 10 feet) can be used to determine the capacitance per foot; do not use too short a length such as one foot, because any error becomes magnified in the total leng th calculations.
Sometimes , the cap aci tan ce of switches, int er co n n ect cables, circuit board foils, or other parts, affecting stray capacitance can be critical to circuit design, or must be repeatable from one unit t o anot her.
Series Vs P a ra llel Measurement (for Indu ctors) The seri es mode dis plays the more accurate me asurement in most cases. The series equivalent mode is essential for obtaining an accurate Q reading of l ow Q inductors. Where ohmic losses are most significant, the series equivalent mode is preferr ed. However, there are cases where the parallel equivalent mode may be more appropriate. For iron core induct or s operating at higher fre quenci es where hysteresis and eddy currents become significant, measurement in the parallel equivalent mode is preferred.
1.4 Accessories
Operating Manual 1 pc
2 AA Size Ni-Mh Rechargeable Batteries 2 pc
19
Shorting Bar 1 pc
AC to DC Adapter 1 pc
TL885A SMD Test Probe 1 pc
TL885B 4-Wire Test Clip (Optional)
TL08C Kelvin Clip (Optiona l)
Carrying Case (Optional)
20

1. NA
2. Primary Parameter Display
5. Model Number
6. Power Switch
7. Relative Key
8. Measurement Level Key
9. Open/Short Calibration Key
10. Measurement Frequency Key
13. Range Hold Key
14. L/C/Z/DCR Fu nction Key
15. Battery Cha rge I ndicator
16. DC Adapter Input Jack
17. Guard Term inal
18. HPOT/HCUR Terminal
2. Operation
2.1 Physical Description
G
H
POT
CUR
UARD
L
POT
LH
CUR
G
UARD
3. Secondary Parameter Display 4. Low Battery Indicator
11. D i splay Update Speed Key
12. D/Q/
21
θ
/ESR Function Key
1
Screws
Battery Compartment Hatch
3
Batteries
4
Norm/Ni-Mh Switch
5
Back Case
6
Tilt Stand
19. LPOT/LCUR Terminal 20. Battery Compartment
2.2 Making Measurement
2.2.1 Battery Replacement When the LOW BATTERY INDICATOR lights up duri ng normal
operation, the batteries in the Models 885 & 886 should be replaced or recharged to maintain proper operation. Please perform the following steps to change the batteries:
1. Remove the battery hatch by unscrewing the screw of the battery compartment.
2. Take out the old batteries and insert the new batteries int o the
battery compartment. Please watch out for battery polarity when installing new batteries.
3. Replace the battery hatch by rever sing the procedure used to
remove it.
2
22
23
!
rechargeable batteries.
Battery Replacement
2.2.2 Battery Recharging/AC operation
Caution
Only the Models 885 or 886 st andar d acces sory AC t o DC adapter can be used with Model 885. Other battery elimina tor or charger may result in damage to Modes 885 or 886.
The Models 885 & 886 works on external AC power or internal batteries. To power the Mode l 885 wi th A C source, make s ure t hat the Models 885 or 886 is off, then plug one end of the AC to DC adapter into the DC jack on the right si de of the instr ument and the other end into an AC outlet.
There is a small slide switch inside the battery compartment called Battery Select Switch. If the Ni-Mh or Ni -Cd rechargeable batteries are installed in Models 885 or 886, set the Batter y Select Switch to "Ni -Mh" posi tion. The Ni-Mh or Ni-Cd batterie s can be recharged when the instrument i s oper at ed by AC source. The LED for indicating battery charging will light on. If the non-rechargeable batteries (such as alkaline bat teries) are i nstalled in Models 885 or 886, set the Battery Select Switch to "NORM" position for disconnecting the charging circuit to the batteri es.
Warning
The Battery Select Switch must be set in the "NORM" position when using non­Non-rechargeable batt erie s may e xplode if the AC a dapter is used with non-rechargea ble batteries. Warranty is voided if this happened.
24
2.2.3 Open and Short Calibrati on The Models 885 & 886 provides open/short calibration
capability so the user can get better accuracy in measuring high and low impedance. We recommend that the user performs open/shor t calibratio n if the test level o r frequency has been changed.
Open Calibration First, remain ing the m easurem ent terminals with the open status, then press the CAL key shor tly ( no mor e t han two s econd) , t he LCD will display:
This calibration ta kes about 10 se con ds. After it is finished, the Model 885 will beep to show that the calibration is done.
Short Calibration To pe rform the short calibration, insert the Shorting Bar into the measurement terminals. Press the CAL key for more t han two second, the LCD will display:
This calibration ta kes about 10 se con ds . After it i s fi nishe d, t he Model 885 will beep to show that the calibration is done.
25
2.2.4 Display Speed
The Models 885 & 886 provides two different display speeds (Fast/Slow). It is controlled by the Speed key. When the speed is set to fast, the display will update 4.5 readings every second. When the speed is set to slow, it’s only 2.5 readings per second.
2.2.5 Relative Mod e
The relative mode lets t he user to make quick sort of a bunch of components. First, insert the standard value compone nt to get the standard value reading. (A pproximate ly 5 seconds in Fast Mode to get a stable reading.) Then, press the Relative key, the primary display will reset to zero. Remove the standard value component and insert the unknown component, the LCD will show the value that is the difference between the standard value and unknown value.
2.2.6 Range Hold
To set the range hold, insert a standard component in that measurement range. (A pproximately 5 seconds in Fast Mode to get a stable reading.) Then, by pressing the Range Hold key it will hold the range within 0.5 to 2 times of the current measurement range. When the Range Hold is press the LCD di splay:
26
2.2.7 DC Resistance Measurement
The DC resistance measurement measures the resistance of an unknown component by 1VDC. Select the L/C/Z/DCR key to make the DCR measurement. The LCD display:
2.2.8
AC Impedan ce Mea s u r em ent
The AC impedance measurement measures the Z of an unknown device. Sele ct th e L/C/Z/DCR key to mak e th e Z m easu rem ent. Th e LCD display:
The testing level and fre quency can by selected by pressing t he
Level key and Frequency key, respectively.
2.2.9 Capacitance Measurement
To measure the capacitan ce o f a com ponent, select the L/C/Z/DCR key to Cs or Cp mode. Due to the circuit structure, t here are two modes can by selected (Serial Mode – Cs and Para llel Mode – Cp). If the serial mode (Cs) is selected, the D, Q and ESR can be shown on the secondary display. If the parallel mode (Cp) is selected, only the D and Q can be shown on the secondary display. The following
27
shows some examples of capacitance measurement:
The testing level and fre quency can by selected by pressing t he
Level key and Frequency key, respectively.
2.2.10 Inductance Measurement
Select the L/C/Z/DCR key to Ls or Lp mode for measuring the inductance in serial mode or parallel mode. If the serial mode (Ls) is selected, the D, Q and ESR can be shown on the seconda ry display. If the parallel mode (Lp) is selected, only the D and Q can be shown on the secondary display. The following shows some examples of capacitance measurement:
The testing level and fre quency can by selected by pressing t he
Level key and Frequency key, respectively.
28


2.3 Accessory Operation
Follow the figures below to attach the test probes for making measurement.
Shorting Bar
TL885A SMD Test Probe
29

H
H
P
C
C
L
L
P

TL885B 4-Wire Test Clip
TL08C Kelvin Clip
30
R
H
CUR
H
POT
DUT
(b) BLOCK DIAGRAM
DUT
V
A
Co
o
L
o
RoL
o
(a) CONNECTION
(c) TYPICAL IMPEDANCE MEASUREMENT RANGE(£[)
2T
1m 10m 100m 1 10 1K 10K 100K 1M100 10M
L
POT
L
CUR
4. Application
4.1 Test Leads Connection
Auto balancing bridge has four terminals (H
) to connect to the device under test (DUT). It i s important to
L
POT
CUR
, H
POT
understand what connection method will affect the measurement accuracy.
2-T e rminal (2T) 2-T erminal is the easiest way to connect the DUT , but it contents many errors which are the inductor and resi stor as well as the parasitic capacitor of the test leads (Figure 3.1). Due to these errors in measurement, the effective impedance measurement
range will be limited at 100
to 10KΩ.
3-T e rminal (3T)
Figure 3.1
, L
CUR
and
31
DUT
V
A
(d) 2T CONNECTION WITH SHILDING
H
CUR
H
POT
DUT
(b) BLOCK DIAGRAM
DUT
V
A
Co
Ro
Lo
Ro Lo
Co doesn't effect measurement result
(a) CONNECTION
(c) TYPICAL IMPEDANCE MEASUREMENT RANGE(£[)
3T
1m 10m 100m 1 10 1K 10K 100K1M100 10M
L
POT
L
CUR
3-Terminal uses coaxial cable to reduce the effect of the parasitic capacitor (Figure 3.2). The shie ld of the coaxial cable should connect to guard of the instrument to increase the
measurement range up to 10M
.
Figure 3.2
4-T e rminal (4T) 4-Terminal connection reduces the effect of the test lead
32
H
CUR
H
POT
DUT
(b) BLOCK DIAGRAM
DUT
V
A
(a) CONNECTION
(c) TYPICAL IMPEDANCE MEASUREMENT RANGE (£[)
4T
1m 10m 100m 1 10 1K 10K 100K 1M100 10M
L
POT
L
CUR
resistance (Figure 3.3). This connection can improve the
measurement range down t o 10m
. However, the effect of the
test lead inductance can’t be eliminated.
Figure 3.3
5-T e rminal (5T) 5-Terminal connection is the combination of 3T and 4T (Figure
3.4). It has four coaxial cables. Due to the advanta ge of the 3T and 4T, this connection can widely increase the measurement range for 10m
to 10MΩ.
33
(d) WRONG 4T CONNECTION
H
POT
DUT
(b) BLOCK DIAGRAM
(a) CONNECTION
(c) TYPICAL IMPEDANCE MEASUREMENT RANGE (£[)
5T
1m 10m 100m 1 10 1K 10K 100K 1M100 10M
H
CUR
DUT
V
A
DUT
V
A
L
POT
L
CUR
4-T e rminal Path (4TP) 4-Termina l Path connection solves the problem that caused by the test lead inductance. 4TP uses four coaxial cables to isolate the current path and the vol tage sense cable (Figure 3.5). The return current will flow through t he coaxial ca ble as well as the
Figure 3.4
shield. Theref ore, the magnet ic flux that generated by i nternal conductor will cancel out the magnetic flux generated by external conductor ( shield). The 4TP connection increase s the
34
(b) BLOCK DIAGRAM
(a) CONNECTION
DUT
V
A
(c) TYPICAL IMPEDANCE
MEASUREMENT RANGE(£[)
4T
1m 10m100m 1 10 1K 10K 100K 1M100 10M
H
POT
DUT
H
CUR
L
CUR
L
POT
H
POT
DUT
H
CUR
L
CUR
L
POT
(d) 4T CONNECTION W ITH SHILDING
measuremen t range from 1mΩ to 10MΩ.
Eliminating the Effect of the Parasitic Capacitor When measuring the high impedance component (i.e. low capacitor), the par asitic capacitor becomes an important issue (Figure 3.6). In figure 3.6(a), the parasitic capacitor Cd is paralleled to DUT as well as the Ci and Ch. To correct this problem, add a guard pla ne (F igure 3.6(b)) in be twee n H and L terminals to break the Cd. If the guard plane is connected to instrument guard, t he effect of Ci a nd Ch will be removed.
Figure 3.5
35
HCUR HPOT LPOT LCUR
HCUR HPOT LPOT LCUR
Cd
DUT
Ch Cl
(a) Parastic Effect
Guard
Plant
Connection
Point
Ground
(b) Guard Plant reduces
Parastic Effect
Figure 3.6
4.2 Open/Short Compensation
For those precision impeda nce mea suri ng instr ument, the ope n and short compensation nee d to be used to reduce the paras itic effect of the test fixture. The parasitic effect of the test fixture can be treated like the simple passive components in figure 3.7(a). When the DUT
ω
is open, the instrument gets the conductance Yp = Gp + j
Cp
(Figure 3.7(b)). When the DUT is short, the instrument gets the
ω
impedance Z s = Rs + j
Ls (Figure 3.7(c)). After the open and short
compensation, Yp and Zs are for calculating the real Zdut ( Figure
3.7(d)).
36
H
CUR
H
POT
L
CUR
L
POT
Zdut
C
o
R
s
L
s
G
o
Z
m
Redundant Impedance
(Z
s
)
Parastic Conductance
(Y
o
)
Parastic of the Test Fixture
(a) Parastic Effect of the Test Fixture
H
CUR
H
POT
L
CUR
L
POT
C
o
R
s
L
s
G
o
(b) OPEN Measurement
Y
o
OPEN
Y
o
= G
o
+ j£sC
o
1
(R
s
+ j£s<< )
G
o
+j£sC
o
H
CUR
H
POT
L
CUR
L
POT
C
o
R
s
L
s
G
o
(c) SHORT Measurement
Z
s
SHORT
Z
s
= Rs + j£sL
s
Figure 3.7
37
Zs
Zm
Yo Zdut
(d) Compensation Equation
Figure 3.7 (Continued)
4.3 Selecting t h e Series or Para llel Mode
According to different measuring requirement, there are series and parallel modes to describe the measurement result. It is depending on the hi gh or low i mpeda nce va lue t o deci de what mode to be used.
Capacitor The impedance and capacitance in the capacitor are negatively proportional. Therefore, the large capacitor means the low impedance; the small capacitor means the high impedance. Figure 3.8 shows the equivalent circuit of capacitor. If the capacitor is small, the Rp is more i mportant than the Rs. If the capacitor is large, the Rs shouldn’t be avoided. Hence, uses parallel mode to measure low capacitor and series mode to measure high capacitor.
Zdut = 1-(Z
Zm - Zs
m-Zs)Yo
38
R
C
R
Effect
No Effect
Large capacitor
R
P
C
R
Effect
Figure 3.8
Small capacitor (High impedance)
(Low impedance)
Inductor The impedance and inductive in the inductor are positively proportional. Therefore, the large inductor equals to the high impedance and vice versa. Figure 3.9 shows the equivalent circuit of inductor. If the inductor is small, the Rs is more important than the Rp. I f the inductor is large, the Rp s hould be taking care of. So, uses series mode to measure low inductor and parallel mode to measure hi gh inductor.
P
S
No Effect
S
39
R
P
L
R
(High impedance)
No Effect
R
P
L
R
Large inductor
Effect
S
Figure 3.9
Small inductor (Low impedance)
No Effect
S
Effect
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