YOKOGAWA 2769 User manual

2769
Portable Double Bridge
User's
Manual
IM 2769-10E
IM 2769-10E
6th Edition: Oct. 2017 (YMI)

IM 2769-10E
―i ―
Introduction
Thank you for purchasing the 2769 Portable Double Bridge.
This User’s manual contains useful information regarding the instrument’s functions and
operating procedures, as well as precautions that should be observed during use.
Before using this product, thoroughly read this manual to understand how to use it properly.
Contact information of Yokogawa offices worldwide is provided on the following sheet.
PIM 113-01Z2: Inquiries List of worldwide contacts
Notice regarding This Document and User’s Manual
• The information covered in this User’s manual is subject to change without prior notice.
• Every effort has been made to ensure accuracy in the preparation of this manual.
Should any errors or omissions come to your attention however,
please inform YOKOGAWA accordingly.
• YOKOGAWA is by no means liable for any damage resulting from
the user’s mishandling of the product.
• This manual is intended to describe the functions of this product.
YOKOGAWA does not guarantee that these functions are suited to
the particular purpose of the user.

IM 2769-10E
―ii ―
Cautionary Notes for Safe Use of the Product
When operating the instrument, be sure to observe the cautionary notes given below to
ensure correct and safe use of the instrument. If you use the instrument in any way other than as
instructed in this manual, the instrument’s protective measures may be impaired.
YOKOGAWA is by no means liable for any damage resulting from use of
the instrument in contradiction to these cautionary notes.
■ The following safety symbols are used on the instrument and in this manual.
Danger! Handle with Care.
This mark indicates that operator must refer to an explanation in
the instruction manual in order to avoid risk of injury or death of
personnel or damage to the instrument.
■ Since mishandling the instrument can result in an accident that may lead to
injury or death of the operator, such as an electric shock, be sure to observe
the following instructions.
WARNING
● Protective Measures
• If a crack appears in the instrument after it has been accidentally dropped or bumped,
the safety-purpose insulation may be damaged.
By all means do not use the instrument, but ask the manufacture for repair.
● Connection
• To avoid electric shock, be sure to apply protective grounding to the grounding terminal.
• Install a protection fuse as shown in the example of measurement.
● Measurement
• Always maintain the instrument within the limits for allowable current, voltage and power,
during operation.
If there is more than one limit for any of these parameters, the lowest limit takes precedence.
● External Power Supply
• Only operate the instrument on a supply voltage no greater than 60 VDC.
● Operating Environment
• Do not operate the instrument in a flammable or explosive gas atmosphere.
• Do not operate the instrument if there is any condensation on it.
● Do Not Remove the Case or Disassemble
• Do not open the case except when replacing batteries or fuse.
Only Yokogawa service personnel are authorized to remove the casing or disassemble or
modify the instrument.
Do not attempt to repair the instrument yourself, as doing so is extremely dangerous.

IM 2769-10E
―iii ―
■ Since mishandling the instrument can result in an accident, such as an electric shock,
that may injure the operator or damage the instrument, be sure to observe
the following instructions.
CAUTION
● Batteries
• Do not use a mixture of different types of batteries or a mixture of old and new batteries.
If the instrument will not be used for a prolonged period, remove the batteries before storage.
The battery fluid will leak more readily during long-term storage, resulting in an instrument
malfunction.

IM 2769-10E
―iv ―
CONTENTS
Introduction ....................................................i
Cautionary Notes for Safe Use of the Product .........................ii
1. GENERAL...................................................1
2. SPECIFICATIONS ............................................1
3. COMPONENT NAMES AND FUNCTIONS .........................3
4. OPERATING INSTRUCTIONS...................................7
4.1 Preparation..............................................7
4.2 Operation for Measurement.................................7
4.3 Accessories .............................................9
5. CAUTIONS.................................................10
5.1 Cautions for Operation....................................10
5.2 Cautions for Maintenance .................................10
5.3 Calibration .............................................10
5.3.1 General Check.....................................10
5.3.2 Check on Operation.................................10
5.3.3 Calibration of Standard Resistor .......................11
5.3.4 Calibration of Measuring Arm Dial ......................11
6. PRINCIPLE OF OPERATION...................................12
6.1 Basic Principles .........................................12
6.2 Error..................................................12
6.2.1 Error due to Current Lead ............................12
6.2.2 Error due to Potential Lead ...........................13
7. CIRCUIT DIAGRAMAND PARTS LIST ...........................15

IM 2769-10E
―1 ―
1. GENERAL
The Portable Double Bridge 2769 is quite convenient with low resistance measurement from
1 mΩ to 110 Ω.
This double bridge contains an electronic galvanometer and bridge power supply to
facilitate the operation.
2. SPECIFICATIONS
Measuring Range: 0.100 mΩ to 110.0 Ω
Accuracy: ±{ 0.05 Ω × (multiplaying factor) + 0.01 mΩ }
at ambient temperature 5 to 35°C, and
the lead resistance between C2 terminals and Rx is less than 20 mΩ.
Measuring Dial: 1.00 to 11.00 Ω, 0.05 Ω minimum division
0.0001 *
0.001
0.01
0.1
1
10
0.1ΩmΩto 1.1 mΩ
1 mΩto 11 mΩ
0.01 Ωto 0.11 Ω
0.1 Ωto 1.1 Ω
1 Ωto 11 Ω
10 Ωto 110 Ω
0.01 Ω
0.1 Ω
1 Ω
10 Ω
100 Ω
1000 Ω
10 A
3 A
1 A
0.3 A
0.1 A
0.01 A
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
±0.1%
Multiply Measuring range Resistance Accuracy Max. current
Standard Resistor
* with an external STANDARD RESISTOR 2771
Table 2.1 Multiply v.s. Standard Resistor

IM 2769-10E
―2 ―
Electronic Galvanometer
Voltage sensitivity: approx. 20 μV/div.
Input resistance: approx. 11 kΩ
Sensitivity dial:
G
0
(input resistance: approx. 11 kΩ)
G
1=
G
2=
G0 (input resistance: approx.11 kΩ)
G0 (input resistance: approx.11 kΩ
）
GA, OFF and B check
1
11
1
110
Power source: 9 V (dry cell Type 006P)
Battery life: approx. 300 h
Bridge Power Source
Voltage: 1.5 V
(dry cell UM-1 or SUM-1, two cell are parallel connected.)
Max. current supply: approx. 1 to 2 A
Battery life: more than 1200 measurement
(50% duty cycle, 15 sec maximum on-time)
Operating Temperature and Humidity Range:
5 to 35°C, Less than 85%
Dimensions: Approx. 182 × 226 × 118 mm (excluding handle and rubber feet.)
Approx. 196 × 226 × 130 mm (including handle and rubber feet.)
Weight: Approx. 2.6 kg (5.7lbs)
Accessories: Plug (A1025WX)
User’s Manual
Carrying case (B9350AW)
Optional accessories: Standard Resistor 277100
(0.01 Ω ±0.1%, with three leadwires)
Approx. 30 × 175 × 63 mm
Approx. 0.25 kg

IM 2769-10E
―3 ―
3. COMPONENT NAMES AND FUNCTIONS
OFF
GA
OFF
BA ON GA
Ω
MULTIPLY
MAX CURRENT (A)
×10
0.01 0.1 0.3 1 3
×1 ×0.1 ×0.01 ×0.001
EXT BA
G2
CH G1
G0
C2S
C2 P2 C1P1P2S
P1S
A
A
(INT BA)
(EXT BA)
Rx
[4]
[3]
[7]
[6]
[2]
[1]
[9][8]
[5] Zero Adjustor
[10]
Rx
20 20
10 10
0
GALVANOMETER
B
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.5
7.0
8.0
7.5
8.5
6.0
2.0
1.5
1.0
11.0
10.5
10.0
9.5
9.0
Front Panel
Fig. 3.1 Front Panel
[1] Measuring Dial
This dial is used to adjust the measuring arm.
[2] Multiplying Factor Switching Plug
The multiplying factor is selected by this plug.
[3] Battery Switch
This switch turns on/off the power to the bridge.
[4] Galvanometer Button Switch
The galvanometer is connected to the bridge by depressing this switch.
This switch is locked by turning it clockwise or counterclockwise while keeping it depressed.

IM 2769-10E
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[5] Galvanometer Sensitivity Dial
The galvanometer sensitivity is selected by this dial;
G0gives the highest sensitivity, G1is medium, and G2is lower than G1.
With this switch, the galvanometer driving battery can be checked through observing the meter.
When the pointer is deflected to the blue zone, this shows that the battery is good.
Also, this switch turns on/off the galvanometer driving battery.
[6] INT. BA Terminals
When the self-contained battery is used to supply power to the bridge,
these terminals are short-circuited by the short-bar.
[7] EXT. BA Terminals
When an external power supply is used, these terminals are short-circuited by the short-bar.
[8] Rx Terminals
An unknown resistance is connected to these terminals.
The Rx terminals consist of current terminals C1, C2and potential terminals P1and P2.
[9] P2S Terminal
This is one of the potential terminals to which the Standard Resistor 2771 is connected.
[10] EXT. BA Terminals
An external battery is connected across these terminals.
The minus (-) side of the terminals is one of the current terminals to
which the External Standard Resistor is connected.

IM 2769-10E
―5 ―
Battery Replacement
The self-contained batteries are located in the bottom of the instrument case.
To open the battery cover, push the clamping plate thoroughly in the arrow direction,
and raise the foot of the cover.
While, to close the cover, push the clamping plate in the arrow direction, fit the edge A-A’ with
the groove of the instrument body, and depress the cover.
The stopper will lock the cover in its place.
Since two batteries are used in parallel connection, replace them with two new ones at a time.
Note that use of old battery in combination with new one will result in short battery life.
Fig. 3.2 Removal of the Battery Cover
A A’
Fig. 3.3 Location of Batteries

IM 2769-10E
―6 ―
Connection for External Battery
When an external battery is used, change the short-bar position
INT. BA terminals to EXT. BA terminals.
Regulate the current by connecting a slide resistor in series to the external battery so as not to allow
current flow in the instrument exceeding the value indicated above the "MULTIPLY" jack and
external standard resistor.
OFF
GA
OFF
BA ON GA
Ω
MULTIPLY
MAX CURRENT (A)
×10
0.01 0.1 0.3 1 3
×1 ×0.1 ×0.01 ×0.001
EXT BA
G2
CH G1
G0
C2S
C2 P2 C1P1P2S
P1S
A
A
(INT BA)
(EXT BA)
Rx
Ammeter
Battery
Slide Resistor
Fig. 3.4 (a) Connection for External Battery
C2 P2 C1P1Rx
Rx
Fig. 3.4 (b) Connection for Rx terminal

IM 2769-10E
―7 ―
4. OPERATING INSTRUCTIONS
4.1 Preparation
(1) Make sure that the INT. BA as well as P2S terminals are shorted securely.
Place the BA switch to OFF position, open the Rx terminals.
(2) Set the GA sensitivity dial to CH position.
By doing this, check that the galvanometer driving battery is good.
When the pointer of the galvanometer deflects to the blue zone on the scale,
this shows that the battery is good.
Note: It takes 1 to 2 seconds for stabilized indication.
(3) Set the GA sensitivity dial to G2, and check that the galvanometer indication is in the zero position.
If deviated, turn carefully the zero adjusting screw of the galvanometer to obtain a true zero point.
(4) Connect an unknown resistance to the Rx terminal.
(Refer to Fig. 3.4 (b) Connection for Rx terminal.)
4.2 Operation for Measurement
(1) Select a multiplying factor by using the plug, to fit the approximating value of the unknown resistance,
according to Table 4.1.
Rx MULTIPLY
0.1 to 1.1 mΩ
1 to 11 mΩ
10 to 110 mΩ
0.1 to 1.1 Ω
1 to 11 Ω
10 to 110 Ω
0.0001
0.001
0.01
0.1
1
10
＊
＊When using 2771
Table 4.1
(2) Turn the BA switch ON.
(3) Set the measuring dial to a position near the center, push the GA button switch momentarily,
and observe the galvanometer.
If the deflection is on the plus (+) side, increase the dial value to obtain zero indication by
repeating the above operation.
When the indication comes near the zero position, push and turn the GA button switch
either clockwise or counterclockwise, to lock the switch.
Then, move the measuring dial to obtain zero indication on the galvanometer.
If the indication is on the minus (-) side in the beginning of this adjustment, reduce the dial value and
obtain zero indication in the same manner as above.
If more sensitivity is required, select G1position first, and G0.

IM 2769-10E
―8 ―
(4) When the galvanometer indication comes to zero through adjustment of the measuring dial,
the resistance value of Rx is calculated from the following equation.
Rx = Indication on
the measuring dial Multiplying
factor
× [Ω
]
(5) When measurement is finished, first release the GA button switch.
Then, turn off the BAswitch and set GA sensitivity dial to
GA
OFF
position.
(6) When it is desired to measure the resistance below 1 mΩ to 0.1 mΩ,
connect the 2771 standard resistor to the instrument as shown in Fig. 4.1.
In this case, the plug should be removed.
The unknown resistance Rx is calculated from the following equation.
Rx = Dial
indication Value of external
standard resistor
× [Ω
]
1
100
2769
Portable Double Bridge
2771
Standard Resistor
0.01 Ω
Rx
C2
MULTIPLY
MAX CURRENT (A)
×10
0.01 0.1 0.3 1 3
×1 ×0.1 ×0.01 ×0.001
EXT BA
C2S
C2 P2 C1P1P2S
P1S
Rx
Fig. 4.1 Connection for External Standard Resistor

IM 2769-10E
―9 ―
4.3 Accessories
(1) Measuring Cord (275300)
The following cords are provided for connection of an unknown resistance:
Current Cord (two) length: 2 m, resistance: approx. 3 mΩ
Potential Cord (two) length: 2 m, resistance: approx. 8 mΩ
Current Cord
Potential Cord
Fig. 4.2 Measuring Cords
(2) Clamping Device (275400)
This clamping device is used for the measurement of a bar resistance of unit length or conductivity.
[length from terminal (P1) to terminal (P2): approx. 500 mm]
C1 P1 P2 C2
Fig. 4.3 Clamping Device
(3) Ammeter
When an ammeter is used for monitoring current through Rx,
remove the short-bar INT. BA (or EXT. BA ) terminals and
the ammeter is connected to these terminals.
For current monitoring, DC Ammeter 2051 (0.3/1/3/10/30 A) is recommended.

IM 2769-10E
―10 ―
5. CAUTIONS
5.1 Cautions for Operation
(1) Insert the multiplying factor switching plug securely into the jack.
(2) Be sure that the GA sensitivity switch is first set to G2position.
Then, proceed to G1, and to G0.
(3) The maximum allowable current of each built-in resistor is indicated on the panel respectively.
Be sure not to exceed this current value. (Refer to Table 2.1 of 2. SPECIFICATIONS.)
(4) Never fail to BA switch to and GA sensitivity dial to
GA
OFF
, when the measurement is completed.
5.2 Cautions for Maintenance
(1) When the instrument is used after a long period of time,
clean carefully the multiplying factor switching plug, dial and
the slide resistor of the measuring dial, with soft clean cloth.
In this case, be careful not to change the contacting pressure of the slider of the slide resistor.
(Avoid using sandpaper or the like when cleaning.)
(2) Remove the self-contain batteries when the instrument is stored for a long period.
(3) The panel and case of this double bridge are made ofABS resin and
has sufficient mechanical strength.
However, they are low resistive against heat and chemicals.
An organic solvent, such as lacquer thinner, should be strictly avoided
when cleaning the panel or case.
5.3 Calibration
Periodic calibration (once a year) is to be conducted in the following manner.
5.3.1 General Check
(1) Check the dials, name plate, terminals, plug, switches, etc., and
see if there are loose connections or defects.
(2) Check if the self-contained battery is exhausted.
5.3.2 Check on Operation
Measure the value of a standard resistor (100 Ω, 10 Ω, ....., 0.001 Ω), and check that
the measured result is within allowable error of 0.5% at 1.0 and 10 on the dial scale.
For this check, use of the 2792A or 2792 Series standard resistor is recommended.
(2792 Series have been discontinued.)

IM 2769-10E
―11 ―
5.3.3 Calibration of Standard Resistor
(R1 to R5, and 2771 standard resistor)
Based on a four-terminal resistor comprising a pair of current terminals C2and C2S,
and a pair of potential terminals P2S and P1S (same as C2) as shown in Fig. 5.1,
measure R1to R5by the double bridge at an accuracy of higher than 0.1%.
Through this operation, obtain the calibrated resistance values of R1to R5.
Then, calibrate the 2771 standard resistor in the same way.
In this case, the current value should be 1/3 the value indicated on the "MULTIPLY" jacks.
For this calibration, use of the 2752 precision double bridge is recommended.
5.3.4 Calibration of Measuring Arm Dial
Connect a calibrated resistor 1000 Ω as an external resistor and then
connect a variable standard resistor (10 Ω to 110 Ω) whose accuracy is 0.1% or better,
to the Rx arm in the ×10 range, and measure its resistance.
The calibrated value is obtained as follows:
=
Calibrated value of
measuring arm dial
100 ×
Resistance value of
standard resistor 1000 Ω
Resistance value of
variable standard resistor
Potential
leads
Current
leads Plug
R1to R5C
2S
P2S
P1S
C2
Fig. 5.1 Calibration of Built-in Standard Resistors

IM 2769-10E
―12 ―
6. PRINCIPLE OF OPERATION
6.1 Basic Principles
Fig. 6.1 shows the theoretical diagram of the double bridge circuit.
When the resistances N and n are adjusted so that the current flowing in
the galvanometer G is reduced to zero, the unknown resistance X is expressed
by equation (6.1) as follows:
X = × S + × –
(6.1)
N
MN Mn
m
m ×
m + n +
Where is the lead resistance from the terminal Ps of S to the terminal Px of X.
The 2769 double bridge is designed so that the fixed resistors and
slide resistors have the following relationship:
(6.2)
N = n and M = m
Therefore,
From equation (6.1),
X = × S
– = 0
N
Mn
m
N
M
In other words, the low resistance X can be accurately measured without influenced by
the lead resistance.
E
G
N
n m
M
Px C2PsX S
Fig. 6.1 Theoretical Circuit Diagram
6.2 Error
6.2.1 Error due to Current Lead
Practically,
N
Mn
m
– is not perfectly zero, but is approximately ±(10-3 to 10-4).
For example,
m + n , 0.99 ,
m
= 10 mΩ
m + n
Then, the second term of equation 6.1 is ±1 × 10-5 Ω.
If S = 0.1 Ω, the resistance value is X = 10-2 Ω ± 1 × 10-5 Ω according to equation (6.1).
This means that the error is ± 1% of the dial reading.

IM 2769-10E
―13 ―
When the value of S is small, namely, X is small, and if the value of /S is large,
a large error will cause no matter how small the value of
N
Mn
m
–may be.
In case of low resistance measurement, the lead resistance between
Ps and C2is designed to be nearly zero.
Therefore, the lead resistance from C2to Rx may be considered as .
In this view, when this double bridge is used in the × 0.0001 range,
arrange" " to be less than 10 mΩ.
6.2.2 Error due to Potential Lead
When the potential lead resistance is large and cannot be neglected, the lead connected across
the potential terminals P1and P2becomes an error of the M and N arms.
While, the individual resistance of M and N arms are not directly related to this error but
the ratio N/M has relation to the error.
Therefore, when the lead resistance is present on the N arm,
the influence of this can be cancelled by adding a lead resistance to the M arm.
This is expressed by the following equation.
(6.4)
X = × S = × S (1 + )
–
(M + M)
(N + N)
N
N
N
N
M
M
on condition that,
1,
M
M1
N
M
In Model 2796 double bridge, a resistance to act as can be connected to the terminals P2S.
The error becomes minimum when
M
M
is equal to
N
N
based on equation (6.4).
Then, find the value of for the measurement where the error due to
the potential lead is 0.5% of the measured value without connecting a resistance
corresponding to .
(6.5)
(6.6)
X = × S = × S (1 + )
From equation (6.4),
The value of should be 1.005. Therefore,
M
N + N N
N
N
N
(1 + )
N = 0.005N
N
M
Model 2769 bridge is designed so that the N = 21 Ω
when the measuring dial scale is minimum (1.0).
Substituting N = 21 Ω for equation (6.6),
N = 110 mΩ

IM 2769-10E
―14 ―
Also, the allowable error of is changed according to the ratio of N/M.
This relationship is expressed by the graph as shown in Fig. 6.2.
For the m and n arms, there are provided no terminals such as corresponding to P2S.
The influence of the lead resistance and upon the m and n arms can be neglected
if the value of is determined sufficiently smaller than that of S.
1
0.5
1.0
0.1
0234 5 6 7 8 9 10 11
0.5% error
N
(Ω)
Dial Scale
Lead Resistance
at Potential
Terminal
Fig. 6.2 Error due to Potential Lead

IM 2769-10E
―15 ―
7. CIRCUIT DIAGRAM AND PARTS LIST
AMP
M
G0
G1
G1
CH
GA OFF
L
HM
GA
BA
R1
R7
R101
S1
BA1
BA2
S3
S2
R11 R13
R9
RV2
RV1
0.1 Ω
13.24 Ω120 Ω390 Ω
1897 Ω
R8
1897 Ω
R10 R12
120 Ω
R6
13.24 Ω
R14
0.3 Ω
R10518 Ω
R104
1 MΩ
10 kΩ
R103
100 Ω
R102
1 kΩ
390 Ω
1 Ω10 Ω100 Ω1000 Ω
P2P1S P1
P1S P2S
C
2S
C
2
P2S C2S
C2 C1
R2 R3 R4 R5
×10×1
(0.01 Ω)
×0.1×0.01×0.001
EXT.
BA
Rx
++
+
+
A
A
(INT.BA) (EXT.BA)