background image

CHAPTER 2  DIAGNOSTIC GUIDE 

Ohaus Corporation  www.ohaus.com 

2-2 

Valor

 7000 Series Service Manual 

2.2.2  Checking Load Cells for Trouble 

1. 

Perform a Resistance Test

, to determine if the Load Cell is severely damaged or a 

short circuit to the frame has occurred.  

Note: 

The Load Cell must be completely disconnected from the Printed Circuit Board 

and at no load when the resistance readings are taken. 

Using an ohm meter, measure and record resistance between each pair of wires 
from the Load Cell, as specified in Table 2-1. Compare the measured readings with 
the specified values in Table 2-1. 

If the resistance readings are in the range specified, skip to the next section. If they 
are outside the expected range, open circuit or short-circuit across any two wires, the 
Load Cell is defective: replace it. (See Chapter 3.) 

TABLE 2-1.  LOAD CELL RESISTANCE READINGS (in Ohms) 

Model 

Ex+ to Ex

  S+ to S

 

Ex+ to S

 

Ex+ to S+

 

Ex

 

to S+

 

Ex

 to S

 

All models 

404 ± 10 

350 ± 4 

289 ± 10  289 ± 10  289 ± 10  289 ± 10 

 
2. 

Perform an Output Voltage Test

:

  

Measure the no load, 50% load and full load 

output.

 

The reading should meet the Load Cell specifications. The Load Cell output 

should be very close to linear over its capacity range.   

NOTE

: The following steps involve power applied to the scale. Load Cell solder 

contacts can be used as measuring points. See Figure 2-1.   

The EXE+ and EXE

 wires should be connected to the PCB, and the SIG+ and SIG

 

wires must be disconnected. Record the colors for each wire connection before 
disconnecting. (See Table 2-2 for typical color code for Valor 7000.)   

TABLE 2-2.  COLOR CODE FOR LOAD CELL WIRING

*

 

AMI 

BLACK 

GREEN 

WHITE 

RED 

 

EXE

 

EXE+ 

SIG+ 

SIG

 

*

Color codes may vary. 

  Insert the Platform Support into the Load Cell Frame, place the Platform on top, 

and turn on power to the scale. 

  Using a voltmeter, measure and record the excitation voltage supplied to the 

PCB:  with no load on the Platform, measure the voltage across points 4 and 1 of 
Load Cell connection on the PCB (+EXE and 

EXE). This voltage must be 

approximately 3.1 Volts dc with the Load cell connected. If the voltage is lower, 
disconnect the Load Cell cable from the PCB and measure again. If the voltage 
is 3.1 Volts dc, the Load Cell is defective and must be replaced. If the voltage 
remains low, the PCB is defective and must be replaced. 

 
 
 
 

Summary of Contents for Valor 7000 series

Page 1: ...SERVICE MANUAL VALOR 7000 Ohaus Corporation 7 Campus Drive Suite 310 Parsippany NJ 07054 973 377 9000...

Page 2: ...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 chang...

Page 3: ...3 Testing the Printed Circuit Board PCB 2 4 2 2 4 Diagnostic Guide 2 6 CHAPTER 3 MAINTENANCE PROCEDURES 3 1 Preventive Maintenance 3 1 3 1 1 Preventive Maintenance Checklist 3 1 3 2 Service Strategy...

Page 4: ...ucture 1 5 2 1 Load Cell Resistance Readings in Ohms 2 2 2 2 Color Code for Load Cell Wiring 2 2 2 3 Load Cell Output Readings in mV with 3 3V Excitation 2 3 2 4 Diagnostic Guide 2 6 3 1 Mounting Bolt...

Page 5: ...ponents Appendix A Standard Calibration Explains procedures for Standard Calibration performed prior to using a scale and after service Appendix B Service Calibration Describes the Service Menu and su...

Page 6: ...0 1 30000 LFT ON Resolution nMax 1 3000 1 3000 1 3000 1 3000 1 3000 Linearity 2d r0 0001 kg r0 0002 kg r0 0005 kg r0 001 kg r0 002 kg Repeatability 2d r0 0001 kg r0 0002 kg r0 0005 kg r0 001 kg r0 002...

Page 7: ...g Press Toggles through active weighing units Short Press in Menu Toggles through available settings Function Mode Back Short Press Selects function setting Long Press Selects active Mode Short Press...

Page 8: ...item 11 in figure 3 2 will remain lit The scale can be operated during charging and the battery is protected against overcharging For maximum operating time the battery should be charged at room tempe...

Page 9: ...O M L O C k E n d Menu Items Reset kg g lb oz lb oz End Reset Stable A Print Contnt Layout Data Tr End Reset Baud Parity Stop Handsh Alt Cm End L Cal L Setup L Read L Mode L Unit L Print L COM End 1 5...

Page 10: ...is not accessible Zero Range is locked at 2 Stable Range setting is locked at 1d Auto Zero Tracking setting is locked at 0 5d Units are locked at their current settings Filter is locked at current se...

Page 11: ...CHAPTER 1 GETTING STARTED Valor 7000 Series Service Manual 1 7 Ohaus Corporation www ohaus com Figure 1 3 Sealing...

Page 12: ...ith the most common cause first If the first remedy does not fix the problem proceed to the next remedy Before attempting to repair the balance read all chapters of this manual to be familiar with the...

Page 13: ...d full load output The reading should meet the Load Cell specifications The Load Cell output should be very close to linear over its capacity range NOTE The following steps involve power applied to th...

Page 14: ...ts at Zero Load 50 and full scale capacities See Table 2 3 for typical readings Figure 2 1 Top view of main PCB NOTE Table 2 3 indicates typical readings Actual values can vary but should remain linea...

Page 15: ...n 3 Using a DVM measure the excitation voltage EXE and EXE in Figure 2 1 The reading should be 3 1 volts dc This is the excitation voltage for the Load Cell and is regulated If the voltage is lower re...

Page 16: ...ue 6 Adjust the Simulator to simulate 0 load 50 load and 100 load for the capacity that the scale is rated for See Table 2 3 for values to use If the resulting readings are unstable the Main PC Board...

Page 17: ...below Power On Zero limit Err 8 3 Over Range Error Weight reading exceeds Overload limit Err 8 4 Under Range Error Weight reading below Underload limit Err 8 5 Tare out of range Adjust tare value to b...

Page 18: ...tronics to stabilize 3 1 1 Preventive Maintenance Checklist The scale should be inspected and checked regularly as follows 1 Remove the Pan and Sub Pan to inspect and clean the area beneath the Pan 2...

Page 19: ...the eight screws holding the Housing in place See Figure 3 1 3 Move the top housing a little bit backward and then raise and remove the top housing 4 Separate Top Housing from Bottom Housing Avoid str...

Page 20: ...PCB to the bottom housing 3 If either the Main PCB or the Load Cell is to be replaced note the order of the wire colors and then disconnect the Load Cell Cable from the Main PCB See Figure 3 2 4 Posit...

Page 21: ...washers that hold the Load Cell assembly frame and load cell to the Bottom Housing Remove the bolts and their washer pairs that hold the Load Cell Frame to the Load Cell Use a high leverage Allen wren...

Page 22: ...ual to the scale s capacity See Table 3 2 There are four Overload Stop Bolts See Figure 3 5 Adjust the Overload Stops per Table 3 2 1 Adjust the Overload Stop Bolt so that the gap between the Load Cel...

Page 23: ...VERLOAD STOP GAP SETTINGS Model Max Capacity Overload Stop Gap V7000 Scale Load Cell A B mm C D mm V71P1501T 1 5kg 3kg 0 6 0 5 V71P3T 3kg 5kg 0 8 0 7 V71P6T 6kg 10kg 1 5 1 1 V71P15T 15kg 20kg 2 4 1 7...

Page 24: ...2 Pull the quick connect tabs free of the battery posts and lift out the battery Figure 3 7 Rechargeable battery 3 Position the replacement battery in the compartment on an angle sufficient to access...

Page 25: ...S REQUIRED The masses required to test the Ohaus Valor 7000 scales must meet the requirements of ASTM Class 4 or OIML F2 Tolerance The mass values are listed in Table 4 1 TABLE 4 1 TEST MASS VALUES Mo...

Page 26: ...ication for each model listed in Table 1 1 1 Power on the balance The reading on the display should be 0g 2 Select a mass weighing near the maximum capacity of the balance and place it on the center o...

Page 27: ...test set up the instrument as follows Set Up Follow the steps in Appendix A Section A 2 Setup and Calibration Record Settings Zero Tracking Setting ____________ Displayed Units ____________ Mass Used...

Page 28: ...ge 6 Mean Reading 1 Reading 2 Reading 3 Reading 4 Reading 5 7 Reading 6 Reading 7 Reading 8 Reading 9 Reading 10 10 Mean ________ 6 Calculate the Delta for each reading and record in the work sheet De...

Page 29: ...press ON Zero Off 3 Place the test mass on the Scale record the weight and remove 4 Place Load 2 on the Scale and press ON Zero Off 5 Place the test mass on the Scale record the weight and remove 6 P...

Page 30: ...test weight in the center of the Weighing Pan 2 Tare the balance 3 Move the weight to point A and record the reading 4 Move the weight to point B and record the reading 5 Move the weight to point C an...

Page 31: ...d NOTE In all cases where a part is replaced the scale must be thoroughly checked after the replacement is made The scale MUST meet the parameters of all applicable specifications in this manual If fu...

Page 32: ...CHAPTER 5 PARTS LISTS DIAGRAMS Ohaus Corporation www ohaus com 5 2 Valor 7000 Series Service Manual 5 1 Valor 7000 SCALES PARTS Figure 5 1 Valor 7000 Scales Parts...

Page 33: ...der Down R31 R21 RC31 RC21 V71 8 30037420 Hardware Kit R31 R21 RC31 RC21 V71 9 30037400 Housing Bottom V71 10 30037421 Feet R31 R21 RC31 RC21 V71 11 30037422 Cover Option R31 R21 RC31 RC21 V71 12 3003...

Page 34: ...libration process 2 Allow the scale to warm up for approximately five minutes after stabilizing to room temperature 3 To abort calibration press Exit key or turn the scale off anytime during the calib...

Page 35: ...accept SpaN will then be shown Press Yes to begin the span calibration 0 kg will be displayed SpaN 0 3 Press Yes to accept C will be displayed while zero reading is stored Next the display shows the c...

Page 36: ...factory Linearity and Span calibrations no pre set limits Note Be careful not to touch the scale or the surface it rests on while calibration is in progress as it will cause the process to fail B 1 S...

Page 37: ...e Service Span Calibration menu Set the graduation of the scale 0 00005 0 02 Grad B 5 Service Span Calibration When SPAN appears press YES to accept the Service Span Calibration menu or No to advance...

Page 38: ...to indicate the calibration unit The example shows the mid calibration point value for a Scale Capacity of 3 kg Place the specified calibration weight on the pan and press Yes C flashes while the mid...

Page 39: ...o the Expand menu item Note Ramp is used to troubleshoot load cell problems 0 represents no signal from the A D 100 reflects the upper signal range of the A D ramMp 0 0 to 100 0 B 8 Expand Menu When e...

Reviews: