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CHAPTER 4  TESTING 

4.5.1   Off Center Load (Shift) Test 

The Off Center Load (Shift) Test is made before and after a Base has had the Load Cell 
replaced and adjustments have been made that affect its performance.  The Off Center Load 
Test verifies that all sections of the Base weigh within specified tolerance.   

If the Base does not pass the Off Center Load Test, verify that the Overload Stops are properly 
set.  (See Section 3.1.)  

If the Off Center Load Test cannot be passed, the Load Cell must be adjusted or replaced.   

Prior to starting this test, the Base must be connected to a properly functioning Indicator, with 
capacity and readability values set according to the specifications for the Base under test. 

1.  Place test weights equal to one third of the Base's capacity sequentially at each of 

the positions A, B, C, and D, as shown in Figure 4-1.  Note the Indicator reading at 
each position.  (For Base capacity, see Table 1-1.) 

2.  Check the variation between mass weights and indicator reading against specified 

Shift Tolerance in Table 1-1. 

 

Figure 4-1.  Positions A, B, C and D are centered  

at each quarter of the base platform. 

CKW Base Series Service Manual 

4-3 

Ohaus Corporation  www.ohaus.com 

Summary of Contents for CKW3R

Page 1: ...SERVICE MANUAL CKW Bases Ohaus Corporation 19A Chapin Road P O Box 2033 Pine Brook NJ 07058 2033 973 377 9000...

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Page 3: ...e 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 c...

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Page 5: ...nce Checks 4 1 4 3 Calibration with an External Indicator 4 1 4 4 Consistency Check 4 2 4 5 Performance Tests 4 2 4 4 1 Shift Test 4 3 4 4 2 Full Load Test 4 3 CHAPTER 5 DRAWINGS AND PARTS LISTS 5 1 C...

Page 6: ...TABLE OF CONTENTS CKW Base Series Scales Service Manual ii Ohaus Corporation www ohaus com...

Page 7: ...Maintenance Procedures Contains preventive maintenance procedures and disassembly repair and replacement procedures Chapter 4 Testing Contains guides for operational and performance tests and adjustm...

Page 8: ...d Cells with connecting cable and hardware Each base contains the following basic replaceable assemblies Platform Load Cell with Connecting Cable and Down Stop and mounting hardware There is an explod...

Page 9: ...2 lb 15 kg x 0 002 kg 30 lb x 0 005 lb 30 kg x 0 005 kg 60 lb x 0 01 lb Maximum Resolution 1 6000 1 7500 1 7500 1 6000 Capacity MAX x Approved Readability e 3 kg x 0 001 kg 6 lb x 0 002 lb 6 kg x 0 00...

Page 10: ...Platform Strain Gauges Beam Printed Circuit Board completing Wheatstone Bridge circuit Holes drilled in Strain Gauge Load Cell Figure 1 1 Typical Strain Gauge Load Cell The strain gauges are wired in...

Page 11: ...gnal is read by the Indicator which converts it to a numeric value and shows it visually This output value increases as weight is loaded to the Load Cell For example a 500kg Load Cell with 2mV V outpu...

Page 12: ...CHAPTER 1 INTRODUCTION Ohaus Corporation www ohaus com 1 6 CKW Base Series Service Manual...

Page 13: ...improper operation of the Base If the Down Stops are improperly set adjust them See Section 3 3 Check the metal surfaces of the Platform All surfaces should be parallel If the platform is deformed it...

Page 14: ...CHAPTER 2 DIAGNOSTIC GUIDE Ohaus Corporation www ohaus com 2 2 CKW Base Series Service Manual...

Page 15: ...the Platform CAUTION DO NOT USE CHEMICAL CLEANERS OR SOLVENTS OF ANY TYPE SOME CLEANERS ARE ABRASIVE AND MAY AFFECT THE SCALE S FINISH 3 Check the Load Cell cable for broken or damaged insulation 4 M...

Page 16: ...load at each corner stop one at a time adjust the round Overload Stop Nut and lock it with the Jam Nut when the Upper Housing just touches the Overload Stop Nut 2 Repeat this for all four corners 3 Fo...

Page 17: ...e Indicator and at no load when these tests are made In addition to the four resistance elements which make up the Wheatstone Bridge there are commonly one or two resistors in the excitation lines The...

Page 18: ...red output readings with the theoretical values from the Load Cell data See Table 4 2 TABLE 4 2 LOAD CELL OUTPUT READINGS in mV with 5V Excitation Model Capacity Zero Load 50 Load 100 Load CKW3 3kg 4...

Page 19: ...sted or replaced Prior to starting this test the Base must be connected to a properly functioning Indicator with capacity and readability values set according to the specifications for the Base under...

Page 20: ...weight to point D and record the reading 7 If the reading at point A is negative file at points 1 and 4 AT AN ANGLE 8 If the reading at point B is negative file at points 1 and 2 STRAIGHT ACROSS 9 If...

Page 21: ...n passed test the Base s full capacity according to the Specification Table 1 1 The Base must meet all specifications as listed 2 If the Base fails the Full Load Test check and set the Down Stops See...

Page 22: ...CHAPTER 4 TESTING Ohaus Corporation www ohaus com 4 6 CKW Base Series Service Manual...

Page 23: ...y checked after the replacement is made The base MUST meet the parameters of all applicable specifications in this manual If further technical information is needed please contact your local Ohaus off...

Page 24: ...CHAPTER 5 PARTS LISTS DIAGRAMS 5 1 CKW CHECKWEIGHER BASES HOUSING PARTS Figure 5 1 CKW Checkweigher Base Housing Parts Ohaus Corporation www ohaus com 5 2 CKW Base Series Service Manual...

Page 25: ...ad Set CKW Base set of 6 5 Load Cell Mounting Bolt 6 Load Cell 7 Load Cell Spacers 8 Level Bracket 10 Column Mount Bolt Kit 11 Down Stop Nut and Jam Nut When replacement parts are needed refer to the...

Page 26: ...CHAPTER 5 PARTS LISTS DIAGRAMS Ohaus Corporation www ohaus com 5 4 CKW Base Series Service Manual...

Page 27: ...ad Over the full rated capacity of the load cell the mV output will change The amount by which it changes depends upon the resistance change in the cell and on the excitation voltage applied Since the...

Page 28: ...APPENDIX A GLOSSARY Ohaus Corporation www ohaus com A 2 CKW Base Series Service Manual...

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Page 30: ...80252592 P N 80252592 SERVICE MANUAL CKW BASES...

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