Seca 606 Service Manual
6061321009
01.05.03
Variants:
6061321619
for seca
Description:
electronic veterinarian scale
606
Content:
Operation 17-10-06-293
Service Manual Number:
17-05-01-316-
Valid as of:
Description display modul 30-34-00-618
Description DMS modul 30-34-00-645 a
Description of faults 30-34-00-588 c
Calibration (lin.) 30-34-00-603
PC configuration program 30-34-00-672 b
cableplan 08-02-06-022 a
Replacement 30-34-00-704
Spare parts 30-34-00-705
Manual number: 17-05-01-316-
Brief description of the display modul e
Introduction
The display modules belong to the family of seca electronic modules and are used to display a weight
measured with a suitable module and transferred via the SeSAM bus (Seca’s Serial Autoconfiguring
Multicontroller bus). Furthermore, the display modules accommodate the operating elements and can
process the weight (hold, tare, etc.).
The following block diagram shows the most important function blocks of the display modules:
Display
I00.00
Backlighting
optional
Quarz
Op eration
SeSAM bus
µC
Id e n tific a tio n
Power on
re set
Signal transm itter
optional
Display
The weight displayed on the LCD is updated approximately every 0.8s. A maximum of five digits as
well as a few special characters can be displayed, which can appear as shown below:
Explanation of the special characters:
• The battery symbol is used to alert of the fact that the battery is going flat.
• The plug symbol indicates that the scale is operated on a mains transformer.
• The warning triangle signals that the weight displayed on the scale is not verifiable.
• Hold indicates that the weight display has frozen.
• Tare or Net show that a weight on the scale has been tared out.
• The left and right arrows point to additional explanations next to the display.
• The weight units on the right show in which unit the measured weight is displayed.
Power supply
Power supply is provided via the SeSAM bus.
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Operation
With the exception of a start button that might be available, the connected buttons can be configured
as required for the particular model. These buttons can be pressed just lightly or longer (longer than
1.5s).
If you press another button when switching on the sc ale, the s cale will s witc h to the v er ification c ounter
and recalibration mode.
SeSAM bus
The SeSAM bus connects the display modules to the other modules. On this bus the stabilized and
non-stablized supply voltages are available. Via a data and a clock pulse line all relevant data is
exchanged. A special start line is prov ided via which the scale can be switc hed on or the module can
signal that it wants to send data.
Identification code
If several display modules are connec ted, an unmistakable ID code must be assigned to them using
soldering jumpers to ensure that the different modules are correctly addressed via the bus.
Backlighting
Some display modules are equipped with a power supply for LCD bac klighting. It c an either be lit when
the scale is switched on or only when the scale is loaded.
Signal transmitter
Some display modules are equipped with a signal transmitter. A piezo diaphragm is used which is
controlled with a 4 kHz square-wave signal.
(optional)
(optional)
Fault handling
If faults occur, the SeSAM bus initiates a fault message with the r elevant fault c ode. F urther mor e, each
fault message includes the number of the module type on which the fault has occ urred and a code
which indicates how long the message is to stay on display and which displays are to be suppressed.
The display module displays its own fault messges on its LCD. Module type (for the display module =
3) and fault number are output. In addition, the fault messages that other modules have transfer red to
the SeSAM bus are displayed.
The following fault messages are implemented:
14 Fault in the kg value calculation
15 Recalibration fault
30 General bus fault
32 Command buffer full
33 More than 8 slaves detected
50 Other fault
51 Menu fault
Time base
From the quartz’s 4.19MHz a time base is derived which controls all timed processes in the scale.
These are, for instance, various timeouts.
Recalibration
In order to compensate for linear measuring errors of the scale, which can, for instance, oc cur as a
result of the different forces of gravity at differ ent geographical points, the module has a recalibration
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function. To initiate the function, another button must be pressed when the scale is started. The
verification counter is then displayed which is incremented whenever the scale is recalibrated. It
enables the user to check whether the scale was manipulated. If, within five seconds, the button is
pressed longer than 1.5 s, the scale switches to recalibration mode. The scale now measures the
zeropoint and waits to be loaded with at least ¼ of the maximum load. By briefly pressing the button
the weight displayed can be decremented or incremented in steps of 10g until the weight of the load
placed on the scale is reached. The direct ion can be changed by pressing the button longer. To stop
recalibration the button must be pressed longer than 5s. T he scale can be switc hed off any time using
the on/off button or by not actuating it for a while, thus aborting recalibration.
Optional functions
The functions “Tare“ , “ Hold“, “ Autohold“ and “ Replace weight in repeat measurements” and various
menu functions can be implemented via a program on the EEPROM (on the weight measuring
module). The functions are explained below:
Tare:
The tare function can be assigned to a button by the EEPROM program. If the button is pressed, the
weight is tared out as soon as the display has settled, if it is within the permissible range. Pressing the
button again alternatively switches the tare function off or causes the weight to be tared out again.
Hold and Autohold:
If the hold function is assigned to a button by means of the EEPROM, the weight reading is held on
display when the button is pressed as soon as the value has stabiliz ed. Alternatively, the hold function
can be automated so that the weight will always be frozen when it has exceeded a certain threshold
and is stable.
The hold function is switched off after expiry of a predetermined time or by pressing the button again.
In addition the scale can be configured so that the hold function will be deactivated when the scale is
relieved, when the scale is relieved and then loaded again and / or when the load on the scale changes
significantly.
Replace weight in repeat measurements:
The scale can be configured so that the weight last displayed is dis played again in a measurement
when the scale detects that it has been loaded with almost the same weight.
Menu functions:
Not all the functions listed below can be activated on the same scale.
When the menu button is pressed long enough, the scale switches to the setting mode. Here, damping
and weight display settings can be made.
When the button is pressed briefly, the scale s witches to function mode. The following functions are
possible:
• BMI: From weight and height the body mass index is calculated using the following formula
2
=
BMI weight kg length m
• IDE: The deviation from the ideal weight calculated using the formula
×-lengthcm
09 100,( [] )
• UL: When a limit weight is overshot or undershot an acoustic signal is generated.
• DIFF: The difference to a second weight is output. The s econd weight can have been measured
using the autohold function, entered manually or stored when the difference function was last
called.
[]/ []
0.9 (height[cm] - 100) is displayed.
BMI = weight [kg] / height [m]2.
Technical data
Supply voltage: 2.7V - 3V and 2.7V - 15V (via SeSAM bus)
Supply current: typ. 0.5mA + power supply for backlighting (typ. 100mA)
Quiescent current: typ. 2µA
Operating temperature: approx. 0°C to 50°C
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Storage temperature: -10°C to 60°C
Dimensions: 74mm x 50mm x 23mm small display
100mm x 84mm x 21mm large display
67mm x 38mm x 23mm backlit display
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Service manual Description of the electronics
Brief description of the DMS module
Introduction
The DMS modules are used to determine weights using a load cell with strain gauges. The DMS low
end module also accommodates the display and the operating unit. To allow the modules to be
adapted to different scales, an EEPROM is integrated which is used to configure the module. A
connection to the SeSAM bus (Seca’s Serial Autoconfiguring Multicontroller bus) is provided via which
the scale can be calibrated and additional modules can be connected.
Display
I0000.
Load cell
A/D Converter
Voltage
control
Operation
EEPROM
Quartz
Temperature
measurement
µC
SeSAM Bus
Power On
Voltage
measurement
Voltage
Reset
control
Mains connection
Battery/rechargeable
batteries
Weight measurement
The DMS modules use load cells with strain gauges in a double bridge circuit as sensors.
The entire analog part runs on its own supply voltage. This voltage can be s witched by the µC to 3V,
5V or 10V. This voltage is also supplied to the load cells. At full load, they deliver a bridge output
voltage of 2mV/V.
This voltage is meas ured by a dual slope a/d converter. The DMS ext module c an evaluate up to four
load cells which are multiplexed acc ordingly. Only one load cell can be connected to the other types of
DMS modules.
The conversion time is selected so that a new measured value is available every 0.1 s.
The resolution of the a/d converter is 0.05 µV/V. If several load cells are connected, k eep in mind that
the resolution relates to the mean output signal of all the load cells connected.
When these meas ured values are within the expected range, they are converted into a weight value
using a third order polynomial. In order to increase accuracy, eight measured values are used to
calculate the weight to be displayed.
The first value obtained after switch-on is used as the zero point. If the values obtained later on do not
deviate strongly from this value, the zero point is corrected in order to com pensate for possible drifts .
(Please also refer to temperature measurement.)
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Service manual Description of the electronics
Display (DMS low-end module only)
Whenever eight new m easured values are available, i.e. approx. every 0.8 s, the weight is displayed.
The display is an LCD which is controlled by duplex operation. A m aximum of five digits as well as a
few special characters can be displayed.
Explanation of the special characters:
• The battery symbol is used to alert of the fact that the battery is going flat.
• Hold indicates that the weight display has frozen.
• Tare or Net indicate that a weight on the scale has been tared off.
• The left arrow indicates if additional explanations are given next to the display.
• The weight units on the right show the unit in which the measured weight is displayed.
Temperature measurement
In order to compensate f or the load cell’s tem perature drift, the tem perature is m easured regularly and
the measured value is adjusted accordingly.
To perform this measurement, a capacitor is charged every 2 seconds alternately via a reference
resistor and an NTC with a linearization resistor connected in parallel. The time until the capacitor has
reached a specific voltage is measured. The temperature is calculated from the ratio of the two times.
To reduce measur ed value fluc tuations, a m ean value of 16 tem perature values is always form ed. The
fluctuation then amounts to approx ±0.2°C.
The difference between the current temperature and the temperature measured when the last zero
point was obtained is used to determine a projected zero point. To do so, one assumes that the weight
change per °C is constant. The weight value is then corrected in accordance with the zero point
calculated and in accordance with the difference to the temperature measured when the scale was
calibrated. A linear and a square term are used for this purpose.
Power supply
Power supply is provided by AA size batteries (batteries or rechargeable batteries) and a plug-in power
supply unit. The batteries pass the voltage via reverse voltage protection diodes to a 3V in-phase
regulator. A coil which suppresses interference and a buffer capacitor come next. This 3 V supply
voltage is supplied to the digital part of the circuit.
Another in-phase regulator generates the voltage for the analog part. T he µC can set this regulator to
3V, 5V or 10V.
In order to operate the module on rechargeable batter ies a recharging circuit c an be connected. T his
circuit charges the rechargeable batteries at a constant current when a power supply unit is connected.
When the supply voltage is applied, a power-on reset is initiated at the µC via an RC element.
To monitor the condition of the batteries, their voltage is m easured ever y 2s. For this purpose, a 2.2 V
reference voltage is integrated upwards and the time until the voltage has r eached approx. 9% of the
supply voltage is measured. Afterwards, a downwards integration is m ade from 2.2V to the threshold.
From these two results, a measured value for the voltage is calculated. If the voltage drops below a
certain limit, the user is aler ted by the battery symbol in the LCD. If the next threshold is undershot,
„bAtt“ is displayed and weighing is no longer possible.
Operation (DMS low-end module only, with the exception of vibration-sensitive
switch and platform switch)
Four buttons are provided; one is used to switch the module on and off, the others can be programmed
as required. These three buttons can be pressed just lightly or longer (longer than 1.5s), so that six
events are available. The actions tare, hold and unit switch-over can be assigned to them.
If you press another button when switching on the scale, the sc ale will switch to the calibration counter
and recalibration mode.
Instead of the normal star t button a piezo diaphragm c an be soldered to the PI c onnection. If the piezo
diaphragm registers a vibration, a transistor s witches and generates an interrupt signal which causes
the µC to start.
If the start button is directly connected to this interrupt input, a button is obtained which is only active
when the scale is switched off. It can be f itted under the platform, for instance, so that the scale is
started by briefly stepping on it.
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Service manual Description of the electronics
Programming
The DMS modules are equipped with an EEPROM which is c ontrolled via the I²C bus protocol. On this
EEPROM all parameters are stored that can be used to inf luence the program s equence. For exam ple
the way the weight is displayed or the allocation of buttons. It also stores the coefficients for
determining the weight and data for temperature compensation, e.g. the factors for the polynomial.
Furthermore, the sc ale can store values to be retrieved when the scale is switched on the next time,
e.g. the weight unit used last.
In order to avoid errors, the EEPROM contents are divided into blocks which are m onitored by cyclic
redundancy checks. The hamming distance is 4 so that single errors can be corrected and double
errors are certainly detected. In addition, values which are recalc ulated when the scale is in operation
can be replaced by default values if an error is detected that cannot be remedied.
Serial bus
To allow the scale to be calibrated and additional modules, such as additional displays, to be
connected, the DMS modules are equipped with an interface to the SeSAM bus.
On this bus the stabilized and non-stabilized supply voltages are available. Via a data and a clock
pulse line all relevant data is transmitted to other modules. A special start line is provided via whic h the
scale can be switched on or other modules can signal that they want to send data.
Both data and start line are open collectors so that they can be switched to low by all modules.
For further details on the bus, please refer to the relevant documentation.
Fault handling
If faults occur, the SeSAM bus initiates a fault mess age with the relevant fault c ode. Fur ther more, each
fault message includes the number of the m odule type on which the fault has occurred and a c ode
which indicates how long the message is to stay on display and which display s are to be suppressed.
The DMS low end module displays its own fault messages on its LCD. Module type (0 for the low-end
module) and fault num ber are displayed. The other DMS modules only transf er fault m essages to the
bus (module type = 1).
The following fault messages are implemented:
10 20 bit counter overflow
11 Counts outside the permissible range
12 Switch-on zero point outside the permissible range
13 Zero follow-up outside the permissible range
14 Fault in the kg value calculation
15 Recalibration fault
20 Battery voltage too low
21 Fault in battery voltage measurement
22 Fault in temperature measurement
23 Temperature range exceeded ( < 0°C or > 50°C)
30 General bus fault
32 Command buffer full
33 More than 8 slaves detected
40 EEPROM fault
41 Incorrect EEPROM access
50 Other fault
Time base
From the quartz’s 4.19MHz a time base is derived which controls all timed processes in the scale.
These are, for instance, various timeouts and the on-time.
After expiry of the on-time, the supply voltage for the analog part, f or voltage m easur em ent and for the
EEPROM is switched off. T he LCD is switched off, all ports are set to zero-s ignal level and the quartz
is stopped.
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