OHAUS SCOUT User manual

OhausCorporation
29HanoverRoad
FlorhamPark,NJ
07932-0900
ELECTRONIC BALANCES
SERVICE MANUAL
TM

The information contained in this manual is believed to be accurate at the time of
publication, but Ohaus Corporation assumes no liability arising from the use or
misuse of this material. Reproduction of this material is strictly prohibited.
Material in this manual is subject to change.
© Copyright 1996, 1998 Ohaus Corporation, all rights reserved.
® Registered trademark of Ohaus Corporation.
SERVICE MANUAL
OhausCorporation
29HanoverRoad
FlorhamPark,NJ
07932-0900
Mode
Off
Re Zero
On
g
TM
TM
Electronic Balances

i
TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION
1.1 Introduction.............................................................................................1-1
1.2 Service Facilities.....................................................................................1-1
1.3 Tools and Test Equipment Required ......................................................1-2
1.3.1 Special Tools and Test Equipment List ..........................................1-2
1.3.2 Standard Tools and Test Equipment List........................................1-2
1.4 Test Masses Required............................................................................1-2
1.5 Specifications..........................................................................................1-3
CHAPTER 2 THEORY OF OPERATION
2.1 Balance Operation ..................................................................................2-1
2.1.1 Operation........................................................................................2-1
2.1.1.1 Turning the Balance ON............................................................2-1
2.2 Transducer Operation.............................................................................2-2
2.3 Printed Circuit Board Circuit Description ................................................2-3
2.3.1 Power Supply..................................................................................2-3
2.3.2 ON/Off Circuitry ..............................................................................2-3
2.3.2.1 Turn On Circuitry.......................................................................2-3
2.3.2.2 Turn Off Circuitry.......................................................................2-3
2.3.3 Low Voltage Detector .....................................................................2-4
2.3.4 Temperature A/D Converter ...........................................................2-4
2.3.5 Full Bridge Weight A/D Convertor...................................................2-4
2.3.6 Half Bridge Emulator.......................................................................2-5
2.3.7 Microprocessor U1..........................................................................2-5
2.3.8 EEPROM U6...................................................................................2-5
2.3.9 Display Driver U7............................................................................2-5
CHAPTER 3 TROUBLESHOOTING
3.1 Troubleshooting ......................................................................................3-1
3.2 Diagnostic Guide ....................................................................................3-1
3.2.1 Diagnosis........................................................................................3-1
3.3 Error Codes ............................................................................................3-4
CHAPTER 4 MAINTENANCE PROCEDURES
4.1 Preventive Maintenance .........................................................................4-1
4.1.1 Preventive Maintenance Checklist..................................................4-1
4.2 Testing ....................................................................................................4-2
4.2.1 Operational Test .............................................................................4-2
4.2.1.1 Segment Display Test ...............................................................4-2
4.2.2 Calibration.......................................................................................4-3
4.2.2.1 Calibration Masses....................................................................4-3
4.2.2.2 Calibration Procedure................................................................4-3
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TABLE OF CONTENTS (Cont.)
CHAPTER 4 MAINTENANCE PROCEDURES (Cont.)
4.2.3 Performance Tests .........................................................................4-6
4.2.3.1 Precision Test............................................................................4-6
4.2.3.2 Off-Center Load Test.................................................................4-7
4.2.3.3 Centered Load Test...................................................................4-7
4.2.4 Down Stop Adjustment ...................................................................4-8
4.3 Replacement of Major Components .......................................................4-9
4.3.1 Disassembly .................................................................................4-10
4.3.1.1 Printed Circuit Board (PCB) (4) and Power Board
Replacement ...........................................................................4-12
4.3.1.2 LCD Display (12) Replacement...............................................4-12
4.3.1.3 Transducer (8) Replacement - 200 Gram Models...................4-13
4.3.1.4Transducer (8) Replacement - 400 and 600 Gram Models .......4-15
CHAPTER 5 DRAWINGS AND PARTS LISTS
5.1 Drawings ..............................................................................................5-1
5.2 Parts Lists ..........................................................................................5-5
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iii
LIST OF TABLES
TABLE NO. TITLE
1-1 Mass Values......................................................................................1-2
1-2 Specifications ....................................................................................1-3
3-1 Diagnostic Guide ...............................................................................3-2
3-2 Error Codes .......................................................................................3-4
4-1 Calibration Masses............................................................................4-3
4-2 Types of Performance Tests .............................................................4-6
5-1 Replacement Parts List .....................................................................5-6
LIST OF ILLUSTRATIONS
FIGURE NO. TITLE
2-1 Display Turn On Sequence ...............................................................2-1
2-2 Strain Gauge Transducer ..................................................................2-2
2-3 Block Diagram ...................................................................................2-6
4-1 Front Panel Controls .........................................................................4-1
4-2 Platform Retaining Screw Location ...................................................4-1
4-3 Display Turn On Sequence ...............................................................4-2
4-4 Down Stop Adjustment Location .......................................................4-9
4-5 Transducer Cross Sectional View .....................................................4-9
4-6 Battery Compartment Location........................................................4-10
4-7 Platform Removal............................................................................4-11
4-8 Cover Removal................................................................................4-11
4-9 Balance Opened..............................................................................4-11
4-10 Bridge Connections .........................................................................4-14
4-11 Transducer Cable Connector ..........................................................4-14
5-1 Exploded View of Balance.......................................................... 5-3/5-4
5-2 PC Board, Schematic Diagram .................................................. 5-5/5-6
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1-1
CHAPTER 1 INTRODUCTION
1.1 INTRODUCTION
This service manual contains the information needed to perform routine maintenance
and service on the Ohaus Scout Electronic Balances, 200g, 400g and 600g capacities.
The contents of this manual is contained in five chapters and are listed as follows:
Chapter 1 Introduction - Contains information regarding service facilities, tools and
test equipment, measuring masses, and specifications.
Chapter 2 Theory of Operation - Contains information on the mechanical and
electronic functions of the balance.
Chapter 3 Troubleshooting - Contains a diagnosis/diagnostics chart and error
message table.
Chapter 4 Maintenance Procedures - Contains preventive maintenance procedures,
performance tests and adjustments, disassembly/replacement procedures, adjust-
ments and calibration procedures.
Chapter 5 Drawings and Parts Lists - Contains an exploded view of the balance
identifying all components and a schematic. Each item on the exploded view is
numbered. These numbers appear in parenthesis throughout the manual after a
particular part to aid in identifying its location which is shown on the exploded view
drawing, Figure 5-1 in Chapter 5.
Before servicing the balance, you should be familiar with the Instruction Manual which
is packed with every balance.
1.2 SERVICE FACILITIES
To service the Scout Electronic Balances, the service area should meet the following
requirements:
• Should be temperature controlled and meet the balance specifications for
temperature environmental requirements. See specifications for tempera-
ture ranges of the various models.
• Must be free of vibrations such as fork lift trucks close by, large motors, etc.
• Mustbefreeofaircurrentsordraftsfromairconditioning/heatingducts,open
windows, people walking by, fans, etc.
• Area must be clean and air must not contain excessive dust particles.
• Work surface must be stable and level.
• Worksurfacemustnotbeexposedtodirectsunlightorradiatingheatsources.

1-2
CHAPTER 1 INTRODUCTION
1.4 TEST MASSES REQUIRED
The masses required to test the Scout Electronic Balances must meet or exceed the
requirements of ASTM Class 4 Tolerance. The mass values are listed in Table 1-1.
TABLE 1-1. MASS VALUES
BALANCE LINEARITY CALIBRATION SPAN CALIBRATION
CAPACITY MASS P/N MASS P/N
200g 100g 51015-05 200g 51025-06
400g 200g (2 required) 51025-06 200g 51025-06
600g 300g (2 required) 51035-05 300g 51035-05
NOTES:
1. A 200 gram mass is supplied with 200g and 400g Scout balances.
2. A 300 gram mass is supplied with 600g Scout balance.
3. Two 100 gram masses are required for linearity calibration on the 200g Scout.
Two 200 gram masses are required for linearity calibration on the 400g Scout.
Two 300 gram masses are required for linearity calibration on the 600g Scout.
4. A total of 300 grams is required for 200g Scout down stop adjustment.
A total of 600 grams is required for 400g Scout down stop adjustment.
A total of 900 grams is required for 600g Scout down stop adjustment.
1.3 TOOLS AND TEST EQUIPMENT REQUIRED
In order to properly service the Scout Electronic Balances, certain Ohaus special tools
and test items are required in addition to standard electronic tool kits. These items are
listed as follows:
1.3.1 Special Tools and Test Equipment List
1. Alternate voltage Power Adapter if local power requirements do not match
Balance Adapter voltage ratings.
1.3.2 Standard Tools and Test Equipment List
1. Standard Electronics Tool Kit.
2. Digital Voltmeter (DVM) Input impedance of at least 10 megohms in the
1 Volt dc position.
3. Mass sets up to 900 grams are required. Ohaus makes various calibration
sets available. Please contact your nearest Ohaus dealer for further details.
4. Soldering iron (25 watt).
5. Solder (rosin core).

1-3
CHAPTER 1 INTRODUCTION
1.5 SPECIFICATIONS
CompletespecificationsfortheScoutElectronicBalancesarelistedinTable1-2. When
a balance has been serviced, it must meet the specifications listed in the table. Before
servicing the balance, determine what specifications are not met.
TABLE 1-2.SPECIFICATIONS
Capacity (g) 200 400 600
Readability (g) 0.01 0.1 0.1
Weighing modes g, oz, oz t, dwt, part counting
Repeatability (Std. dev.) (g) 0.01 0.1 0.1
Linearity (g) 0.01 0.1 0.1
Tare range To capacity by subtraction
Over range capacity 103%
Stabilization time (seconds) 3 3 3
Sensitivity drift (%/°C) ±0.005 ±0.02 ±0.02
Zero point drift (g/°C) 0.03 0.5 0.5
Shift accuracy
(1/2 capacity, 1/2 distance) (g) 0.01 0.1 0.1
Operating temperature 50° to 104° F/10° to 40° C
Operating humidity range 10% to 85% RH
Power requirements AC Adapter (supplied with balance)
100, 120, 220, 240 V ac, 50/60 Hz
or one 9 V Battery (not included)
Typical battery life (hours) 13 16 16
Display (in/cm) LCD (0.7/1.8 high)
Pan size (W x H x D) (in/cm) 4/10.2 dia. 5 x 5.75/ 5 x 5.75/
12.7 x 14.6 12.7 x 14.6
Dimensions (W x H X D) (in/cm) 6.75 x 2.4 x 8.25/17.1 x 6.2 x 21
Net weight (lb/kg) 1.5/0.7 1.8/0.8 1.8/0.8
Shipping weight (lb/kg) 3.2/1.5 3.5/1.6 3.7/1.7
Item No. SC2020 SC4010 SC6010

1-4
CHAPTER 1 INTRODUCTION