Download KERN & Sohn GmbH

KERN & Sohn GmbH
D-72322 Balingen-Frommern
Postfach 4052
E-Mail: [email protected]
Tel: 0049-[0]7433-9933-0
Fax: 0049-[0]7433-9933-149
Internet: www.kern-sohn.de
Service Manual
Electronic Precision Balances
page 2
KERN HUS
version 1.0
HUS-SH-e-0110
KERN HUS
version 1.0
Service Manual
Electronic Precision Balances
Table of Content
1. INTRODUCTION …………………………………………………………. 3
2. SPECIFICATION ………………………………………………………….
2.1 System Block Diagram ……………………………………………...
2.2 Physical Layout of Electrical Connection ………………………….
2.3 General Specification ………………………………………………..
2.3.1 Overall View ………………………………………………..
2.3.2 Dimensions …………………………………………………
2.3.3 Model Specification ………………………………………..
2.3.4 Operating Conditions ………………………………………
2.3.5 Main Components …………………………………………
2.3.6 Analog Specification ……………………………………….
2.3.7 Capacity & External Division ……………………………..
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3. INITIAL SETUP …………………………………………………………….
3.1 Internal Functions and Alternate Division ………………………….
3.2 Auto and Dealer Calibration …………………………………………
3.3 Disable Calibration with Dip Switch (S1) …………………………..
3.4 Offset and Span Value Data ………………………………………..
3.5 Flow Chart …………………………………………………………….
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4. TROUBLE SHOOTING …………………………………………………… 16
4.1 Trouble Shooting Loop ………………………………………………. 16
4.2 Parts and Components Trouble Shooting …………………………. 17
4.2.1 Power Supply Check ………………………………………. 17
4.2.1.1 Relevant Parts ………………………………….. 17
4.2.1.2 Input Voltage: 5.5V or less …………………….. 18
4.2.1.3 Output Voltage of Regulation: 5V +/- 10% …… 18
4.2.2 Load Receptor Check ………………………………………. 18
4.2.3 LCD Display Check …………………………………………. 18
4.2.4 CPU Check …………………………………………………… 18
5. ELECTRICAL CIRCUITRY ………………………………………………… 19
5.1 Schematics ……………………………………………………………... 19
5.2 PCB Layout ……………………………………………………………... 21
6. PARTS LIST ………………………………………………………………….. 22
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1. INTRODUCTION
Features of the KERN HUS series:
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Full Tare
Tare indicator
Zero indicator
Negative value indicator
Special hold function
2 types of calibration
dip switch to prevent end-user calibration
optional backlighting
built-in rechargeable battery
operating time after fully charged 120 hrs.
low-battery signal
auto power saving function
AC adaptor included
LCD display – easy to read
Optional IR remote controller
Capacity: 60 kg, 150 kg, 300 kg, 600 kg
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2. SPECIFICATION
2.1 System Block Diagram
Description: When a load is applied to the loadcell, the resistance to the
excitation current in the strain gauge changes and the analog output signal
varies. It is amplified and digitalized continuously by the A/D converter into a
digital signal. Subsequently, the resulting count is processed and managed by
the CPU. The CPU refers to the instructions from the keyboard and then
conveys the output data to the LCD driver which formats the data into a
readout for the display.
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2.2 Physical Layout of Electrical Connection
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2.3 General Specification
2.3.1 Overall View
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2.3.2 Dimensions
142mm width / 152mm length / 360mm height
----
60 to 300 kg
capacities
142mm width / 152mm length / 378mm height
----
600kg capacity
2.3.3 Model Specification
Display resolution:
Internal resolution:
Display:
1/3,000 (60kg, 150kg, 300kg, 600kg)
1/30,000
single-sided weight display with 5 digits
2.3.4 Operating Conditions
Power source:
Rechargeable battery (6V 10 Ah / 6V 4 Ah)
or AC adaptor (DC 15V, 500mA / DC 9V, 500
mA)
0°C to 40°C
15% to 85% RH
1W/0.1W; 5W when charging
Operating temperature:
Operating humidity:
Power Consumption:
2.3.5 Main Components
Micro processor:
Crystall oscillator:
Display device:
Loadcell:
89C51/80C31
6 MHz / 7.3728 MHz
7 segments LED display / Liquid Crystal Display
(LCD)
350 resistance loadcell
2.3.6 Analog Specification
Input sensitivity:
Zero adjust range:
Zero balance range:
L/C applied voltage:
Speed of A/D conversion:
Internal resolution:
2mV/V
2% R.O.
+/- 5% R.O.
DC 5V
4 times / sec.
30,000
2.3.7 Capacity & External Division
MODEL NO.
HUS60K20
HUS150K50
HUS300K100
HUS600K200
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CAPACITY
60 kg
150 kg
300 kg
600 kg
EXTERNAL DIVISION
0.02 kg
0.05 kg
0.1 kg
0.2 kg
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3. INITIAL SETUP
3.1 Internal Functions and Alternate Division
Internal Function Table
FUNCTION
SYMBOL
1
F.1
2
F.2
3
F.3
4
F.4
DESCRIPTION
Span value reading and dealer calibration
Full display segment and max. capacity check
Check offset value and scale configuration
Auto power off setting
How to enter the required function mode:
a. Turn scale off
b. Press and hold TARE, then turn scale on. Scale displays F.1
c. Press TARE until the required function number appears
d. Press MODE
e. Press MODE until the required setting appears
f. Press TARE to confirm
g. Repeat steps c. to f. for other function setting, or
h. Press ZERO to save settings and return to normal operation
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F.1
Span value reading and dealer calibration
Simply enter F.1, then put on the designated mass to check span value
or keep going to do dealer calibration
F.2
Display segment and rated capacity & division check
When function is entered, scale will first display the rated capacity and
Division, then display all segment. Check and make sure that no
segment is missed.
F.3
Check offset value is within acceptable range and scale configuration
1. Enter F.3, scale displays the offset value
2. Hold MODE for about 2 sec.
3. Scale displays capacity and division configuration
4. Press MODE until the required configuration is obtained. Note: In
some countries, only the metric weight unit is available.
5. Press ZERO to save setting and go back to normal operation status.
F.4
Auto power off setting
Two modes are available: (Default=4_OFF)
0._OFF = auto power off function is disabled
4._OFF = scale will automatically get turned off after 4 min. unused
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3.2 Auto and Dealer Calibration
Acceptable load for auto and dealer calibration
MODEL-NO.
HUS60K20
HUS150K50
HUS300K100
HUS600K200
EXTERNAL
DIVISION
1/3,000
1/3,000
1/3,000
1/3,000
ACCEPTABLE AUTO AND DEALER
CALIBRATION LOAD
20 kg
40 kg
100 kg
200 kg
40 kg
100 kg
200 kg
400 kg
Dealer calibration procedure:
1. Turn scale off
2. Press and hold TARE, then turn scale on
3. scale displays F.1
4. Press MODE
5. Scale displays offset value
6. Press ZERO to zero offset value
7. Press TARE
8. Press ZERO
9. Press TARE
10. Press ZERO, an arrow will appear at the right hand side of the display. It
indicates that the scale is ready for dealer calibration.
11. Make sure that the displayed figure is “0” or “1”. If not, press ZERO again.
12. Load calibration of each load as listed in above table.
13. When displayed value is stable, press MODE.
14. Wait until the scale starts to count down.
15. Calibration is completed and scale is ready for operation.
Auto calibration procedure:
1. Turn off scale.
2. Press and hold MODE, then turn on the scale.
3. Scale displays “CAL?”
4. Press MODE
5. Scale displays “LOAD XXXX” or “XXXX”
6. Load calibration, load according to above table
7. Wait until the scale displays “DONE” and starts to count down.
8. Calibration is completed and scale is ready for operation.
3.3 Disable Calibration with Dip Switch (S1)
The Dip switch #1 is used to control calibration. Push the switch to “ON”
position to disable calibration.
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3.4 Offset and Span Value Data
MODEL-NO. EXTERNAL
DIVISION
OFFSET
VALUE
(thousand)
HUS60K20
1/3,000
4~7
HUS150K50
1/3,000
4~7
HUS300K100
1/3,000
4~7
HUS600K200
1/3,000
4~7
SPAN VALUE
(thousand) AT
VARIOUS
APPLIED LOADS
8~12 at 20kg,
20~30 at 50kg
8~12 at 50kg,
16~24 at 100kg
8~12 at 100kg,
20~30 at 200kg
8~12 at 200kg,
20~30 at 500kg
OFFSET
CONTROL
VR1 Trimmer
SPAN
CONTROL
(Ohm)
R1A R1B
40K
x
VR1 Trimmer
40K
x
VR1 Trimmer
40K
x
VR1 Trimmer
40K
x
Reading offset value:
1. Turn scale off.
2. Remove all load from the platter.
3. Enter F.3 and read the offset value.
Reading span value:
1. Turn scale off.
2. Remove all load from platter.
3. Enter F.1
4. Press ZERO
5. Apply load to platter. Span value according to applied load will be
displayed.
How to adjust offset value:
In case the offset value is out of range, adjust the trimmer located at VR1
(TR2) on the mainboard to obtain correct offset value.
How to adjust span value:
The span value is controlled by resistor located on R1A and R1B. Standard
resistor value of R1A and R1B is listed in the above table.
If the required span value is not attained, then change R1A and/or R1B
resistor according to either case below:
Span value too low: Increase the resistance of R1A and/or R1B.
Span value too high: Decrease the resistance of R1A and/or R1B.
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3.5 Flow Chart
Auto-calibration (for end-user)
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Function Test (for technicians only)
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4. TROUBLE SHOOTING
4.1 Trouble Shooting Loop
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4.2 Parts and Components Trouble Shooting
4.2.1 Power Supply Check
4.2.1.1 Relevant Parts
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Description:
1. AC adaptor: This AC adaptor provides about 9-12V DC power.
2. Battery: Built-in rechargeable battery 6V 4 Ah
3. How battery is charged completely? The charging voltage is regulated by
Q1(C1061) and ZD1(8.2V) for about 7 volts. The charging current will go
down automatically if the battery’s voltage is reached. Q2(C945) and
R1(1.2R, 1/2W) provide over-current protection.
4. Charging status indications: LED turns RED (or ORANGE) → charging;
LED turns GREEN → fully charged
5. Auto-off: If the scale is set on 4_OFF or even under LO-BAT situation after
some minutes the CPU will release a negative pulse to cut off Q4
transistor, then Q1 will be cut off too. The scale is shut down immediately.
4.2.1.2
Input Voltage: 5.5V or less
Check and recharge battery if voltage is less than 5.5V.
Check and replace DC-JACK or AC adaptor if defective.
4.2.1.3
Output Voltage of Regulation: 5V +/- 10%
Check that the output voltage is within 5V +/- 10%. At less than 2.7V the
CPU may not work properly. At more than 6V ghost will appear on LCD.
4.2.2 Load Receptor Check
The load receptor device shall not touch anything around itself during
operation. Check that the load receptor is not contacted with the upper (no
load) and/or lower (with load) stopper.
4.2.3 LCD Display Check
Check that it is soldered and connected properly between LCD and driver
IC(uPD7225), driver IC(uPD7225) and CPU.
Check whether LCD is broken.
4.2.4 CPU Check
Check that all pins are seated properly into the socket.
Check that the crystal oscillator works.
Check that RESET is normally low.
When no error is found with the above checking procedures, the trouble can be
caused by the loadcell or the PCB itself. Replace them by new components could
be suitable to identify the cause of the trouble. In this way, the readout of weight
would be varied because of the output voltage of the loadcell and the different
span value. Therefore, re-calibration is required after this replacement.
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5. ELECTRICAL CIRCUITRY
5.1 Schematics
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5.2 PCB Layout
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6. PARTS LIST
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