YOKOGAWA 279301 User manual

2793 (279301, 279303)
Decade Resistance Box
User's
Manual
IM 2793-01E
IM 2793-01E
8th Edition: Oct. 2017 (YMI)

IM 2793-01E
―i ―
Introduction
Thank you for purchasing the 2793 Decade Resistance Box.
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.
Keep this manual in a safe place for quick reference in the event that a question arises.
Contact information of Yokogawa offices worldwide is provided on the following sheet.
PIM 113-01Z2 Inquiries List of worldwide contacts
Notes
• The information contained in this manual is subject to change without notice.
Furthermore, the actual display items may differ slightly from the ones appearing in this manual.
• Every effort has been made to ensure the information contained herein is accurate.
However, should any concerns, errors, or emissions come to your attention, or if you have any comments,
please contact us.
• Copying or reproduction of any or all of the content of this manual without Yokogawa’s permission is strictly
prohibited.

IM 2793-01E
―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.
This manual is an essential part of the product; keep it a safe place for future reference.
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 the manual:
Danger! Handle with Care.
This symbol indicates that the operator must refer to an explanation in
the User’s Manual or Service Manual in order to avoid risk of injury or
loss of life of personnel or damage to the instrument.
WARNING
Indicates a hazard that may result in the loss of life or serious injury of the user unless
the described instruction is abided by.
CAUTION
Indicates a hazard that may result in an injury to the user and/or physical damage to
the product or other equipment unless the described instruction is abided by.

IM 2793-01E
―iii ―
■ 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
● 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.
• Only operate the instrument on an input-to-ground supply voltage of no greater than 250 V
(except for Model 279303).
• When an input-to-ground supply voltage of greater than 250 V needs to be applied to Model 279303,
exercise extra care when handling the instrument.
• The terminals and internal circuitry may become electrified to high voltages and extremely hot depending on
the instrument’s condition of use. Do not touch these parts.
● Grounding
• To avoid electric shock, be sure to apply protective grounding to the grounding terminal.
● 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 manufacturer for repair.
● 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 Casing or Disassemble
• 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.
(If you are rack-mounting the instrument, use it correctly according to the handling procedure.)

IM 2793-01E
―iv ―
CONTENTS
Introduction...................................i
Cautionary Notes for Safe Use of the Product........ii
1. GENERAL ................................ 1
2. NAMES AND FUNCTIONS OF COMPONENTS ... 1
3. SPECIFICATIONS .......................... 2
4. CIRCUIT DIAGRAM......................... 3
Disposing the Product ......................... 4
8th Edition: October 2017
All Rights Reserved. Copyright © 1991, Yokogawa Electric Corporation,
2017, Yokogawa Test & Measurement Corporation

IM 2793-01E
―1 ―
1. GENERAL
The 279301 and 279303 Resistance Boxes are high-accuracy variable resistors with 6 dials.
Setting of these instruments is easy over wide resistance range.
The 279301 has resistance range of 0.1 to 1111.210 Ω in 1 mΩ steps and
accuracy of ±0.01%.
It is best suited for calibration of resistance thermometers.
The 279303 has resistance range of 0 to 111.1110 MΩ in 100 Ω steps and
accuracy of ±0.05%.
It is best suited for calibration of insulation resistance testers.
These Decade Resistance Boxes employ in-line display system,
and rack-mounting is possible.
2. NAMES AND FUNCTIONS OF COMPONENTS
[ 1 ]
Resistance Terminals
[ 2 ]
Resistance Setting Decade Dials
[3]Earth Terminal
[ 4 ] Outer Case
[5]Carrying Handle
[ 3 ]
[ 2 ][ 1 ] [ 5 ] [ 4 ]

IM 2793-01E
―2 ―
3. SPECIFICATIONS
Resistance Range:
Dial Composition:
Resolution:
Accuracy:
0.100 to 1111.210 Ω
0.001 Ω × 10 + 0.01 Ω × 10 +
0.1 Ω × 11 + 1 Ω × 10 + 10 Ω × 10 +
100 Ω × 10
0.001 Ω
± (0.01% + 2 mΩ)
279301
Temperature Coefficient:
(At temperature 23 ± 2º
C, humidity 45 to 75%)
Input Power: Max.0.1 W
More than 500 MΩ (at 500 VDC)
between panel and circuit
0.25 W per step
Within 1 W for overall instrument
Temperature Raise: Less than 30ºC
at maximum power rating.
Max. Allowable Power:
Max. Allowable Current:
Insulation Resistance:
1000 VAC 1 minute
between panel and circuit
Approx. 116 × 497 × 140 mm
Approx. 4.8 kg
User's Manual 1 copy
Dielectric Strength:
Dimensions:
Weight:
Accessory:
(×10-6/ºC)
(×10-6/ºC2)
α
β
20
T.C. Dial 100 Ω
step
10 Ω
step
1 Ω
step
0.1 Ω
step
−5 to +10
−0.3 to −0.7
−5 to+20 Approx. *
20 to 90
Approx. *
90 to 900
Rt = R {1 + α (t − 20) + β (t − 20) }
2020 2
20
Rt : Resistance Value at tºC
R : Resistance Value at 20ºC
* Inculuding T.C. of wiring and switches resistance
(60 μΩ/ºC)
100 Ω step
10 Ω step
1 Ω step
0.1 Ω step
50 mA
150 mA
500 mA
1.5 A
Resistance Range:
Dial Composition:
Accuracy:
0 to 111.1110 MΩ
100 Ω × 10 + 1 kΩ × 10 +
10 kΩ × 10 + 100 kΩ × 10 +
1 MΩ × 10 + 10 MΩ × 10
279303
Temperature Coefficient:
(At temperature 23 ± 2ºC,
humidity below 75%,
incuding residual resistance approx. 0.05 Ω
)
More than 1011 Ω (at 1000 VDC)
between panel and circuit
Max. Allowable Input (Current
∙ Voltage):
Insulation Resistance:
2500 VAC 1 minute
between panel and circuit
Approx. 116 × 497 × 140 mm
Approx. 4.8 kg
User's Manual 1 copy
Dielectric Strength:
Dimensions:
Weight:
Accessory:
100 Ω, 1 kΩ, 10 kΩ, and 100 kΩ step
± (0.05% + 0.05 Ω)
1 MΩ and 10 MΩ step
± 0.2%
10 kΩ, 100 kΩ, 1 MΩ, and 10 MΩ step
100 Ω and 1 kΩ step
Rt = R {1 + α (t − 20) + β (t − 20) }
2020 2
α = (− 2 to +20) × 10-6/ºC
β = − (0.3 to 0.7) ×10-6/ºC
20 2
±30 ×10-6/ºC
20
Where Rt : Resistance Value at tºC
R : Resistance Value at 20ºC
Variation of resistance with temperature change is
shown in the following equation:
100 Ω step
1 kΩ step
10 kΩ step
100 kΩ step
1 MΩ step
10 MΩ step
100 mA
30 mA
10 mA
3 mA
2000 V
2000 V
2000 V
(100 kΩ to 600 kΩ)
(700 kΩ to 1 MΩ)

IM 2793-01E
―3 ―
4. CIRCUIT DIAGRAM
R610
R609
R608
R607
R600
R606
R605
R604
R603
R602
R601
3.54 Ω
3.42 Ω
3.31 Ω
3.19 Ω
0.06 Ω
3.08 Ω
2.97 Ω
2.86 Ω
2.76 Ω
2.65 Ω
2.55 Ω
R509
R507
R505
R503
R502
0.9 Ω
0.56 Ω
0.3 Ω
0.12 Ω
0.06 Ω
R501
R504
R506
R508
R510
0.02 Ω
0.2 Ω
0.42 Ω
0.72 Ω
0.1 Ω
R309
R307
R305
R303
R302
90 Ω
56 Ω
30 Ω
12 Ω
6 Ω
R301
R304
R306
R308
R310
2 Ω
20 Ω
42 Ω
72 Ω
10 Ω
R209
R207
R205
R203
R202
900 Ω
560 Ω
300 Ω
120 Ω
60 Ω
R201
R204
R206
R208
R210
20 Ω
200 Ω
420 Ω
720 Ω
100 Ω
R409
R407
R405
R403
R402
9 Ω
5.6 Ω
3 Ω
1.2 Ω
0.6 Ω
R401
R404
R406
R408
R410
0.2 Ω
2 Ω
4.2 Ω
7.2 Ω
1 Ω
R1
0.02 Ω
Fig. 1.1 Circuit Diagram
279301
S6S5S4S3S2S1
R104
1000 Ω
R105
1000 Ω
R103
200 Ω
R102
200 Ω
R101
100 Ω
R601
R602
R603
R604
R605
R606
R607
R608
R609
R610
100 ΩR501
R502
R503
R504
R505
R506
R507
R508
R509
R510
1 kΩR401
R402
R403
R404
R405
R406
R407
R408
R409
R410
10 kΩR301
R302
R303
R304
R305
R306
R307
R308
R309
R310
100 kΩ
R121
5 MΩ
R122
5 MΩ
R119
5 MΩ
R120
5 MΩ
R117
5 MΩ
R118
5 MΩ
R115
5 MΩ
R116
5 MΩ
R113
5 MΩR114
5 MΩ
R111
5 MΩR112
5 MΩ
R109
5 MΩR110
5 MΩ
R107
5 MΩR108
5 MΩ
R105
5 MΩR106
5 MΩ
R103
2.5 MΩR104 2.5 MΩ
R102
2.5 MΩR101 2.5 MΩ
R202
200 kΩR201 200 kΩ
R206
500 kΩ
R207
500 kΩ
R208
500 kΩ
R209
500 kΩ
R210
1 MΩ
R211
1 MΩ
R212
1 MΩ
R213
1 MΩ
R214
1 MΩ
R215
1 MΩ
R216
1 MΩ
R205
200 kΩ
R203
200 kΩR204
200 kΩ
S6S5S4S3S2
HL
S1
Fig. 1.2 Circuit Diagram
279303

IM 2793-01E
―4 ―
Disposing the Product
Waste Electrical and Electronic Equipment (WEEE), Directive
(This directive is valid only in the EU.)
This product complies with the WEEE directive marking requirement.
This marking indicates that you must not discard this electrical/electronic product in
domestic household waste.
Product Category
With reference to the equipment types in the WEEE directive,
this product is classified as a “Monitoring and control instruments” product.
When disposing products in the EU, contact your local Yokogawa Europe B.V. office.
Do not dispose in domestic household waste.

Printed in Japan