Olympic 50 User manual

CAUTION: This product should be used
only under the supervision of a licensed
medical practitioner.
SECTION TWO: OPERATION
Controls and Signals .......... Liveri ーー 2-1
Operation-AC or Battery ............. ーー ーーー 2-2
To Turn On/OfF uses 2-2
Adjusting Platform Ends .......i...... 2-2
Weighing child ............. 0” 2-2
Weight Lock/Unlock ........ iii 2-2
Recalling LastLockedWeight.......................... 2-2
ToWeighNeztChild........................... 2-2
. Pounds/Ounces to Kilograms Li nnncnancnno nino 2-3
"E OLYMPIC MEDICAL
| 5900 First Ave So « Seattle, WA 98108 « USA
SS50-N1-220V(B09)
INSTRUCTIONS
SMART SCALE,
— Model 50
220/240 VAC, 50/60 Hz, 10W ‘
SECTION ONE: SUMMARY OPERATING Cancelling Weight of Objects on Platform .......
ーー . INSTRUCTIONS |
Overload ss
To Adjust Platform ............. ーー 다이아나 11° Cleani .
eaning............................. siii
TolowerEnds................................. ο. 1-4 | Battery Operation i
To Raise Ends 4x... 1-1 o
TolurnOn.......................... 0” 1-1
To Weigh Child .................. ev 1-1 SECTION THREE: INSTALLATION
To Reweigh Child ............ 2 1-1 SteatilonaryüÜse.............................. pece
To Recal WeigRt ii 1-1 PortableUse...............................
To
Weigh
Next
Child...
die
1-1
Electrical
Requirements
..................
ir
="
To Cancel Out Weight of Objects....................... 1-1 Initial Battery Charge nana
To Change Kilograms to Pounds/Ounees ......... 1-1 Carrying Soale ON
Calibration Check ................ 用
Troubleshooting ......................1.................
Symptoms and Suggested Tests ................ o
Theory of Operation ..........!..........................
For information or assistance
Call Toll-Free 1 800 426-0353

Section One
Summary Operating Instructions __ otymerc smarrscatz,
Model 50
To Adjust Platform
- One or both ends may be lowered depending on size of child.
To Lower Ends(s)
- While holding end, press red button and then lower end.
To raise end(s)
- Lift end as high as possible and until red button pops out and the word
LATCHED appears on the top of the button.
To Turn On
- Push On/Off button. Wait until zero weight appears on display.
To Weigh Child
« Place child on platform. Note: Sides and ends are part of weighing platform.
- Ifchild is active, press Average/Unlock button. Wait for Averaging light to stop
biinking and Locked light to come on. Read weight.
- Do not touch platform while Averaging light is blinking.
To Reweigh Child
- Press Average/Unlock button to unlock display.
- Press Average/Unlock again. Wait for Averaging light to stop blinking and
Locked light to come on. Read weight. |
To Recall Weight
- If Scale is turned off, press Recall to display last locked in weight.
To Weigh Next Child
- If locked, press Average/Unlock button to unlock display.
- Place child on platform.
- Press Average/Unlock button. Wait for Averaging light to stop blinking and
Locked light to come on. Read weight.
To Cancel Out Weight of Toys, Blankets or Other
Objects
- IfScale is off, place object on platform. Turn Scale on and wait for zero weight
to appear. Then place child on platform and proceed with weighing.
- IfScaleis turned on, place object on platform and press Zero button After zero
weight appears in display, place child on platform and proceed with weighing.
To Change Kilograms to Pounds-Ounces and Vice Versa
- Press Kg/Lb button.
For Information
Please call toll-free
1 800 426-0353
SS50-N1-220V(B09) Page 1-1.

Section Two
Operation
Model 50
Controls and Signals
Foid-down
Fold-down
A
End
Latch Button
End
Ends and sides
are part of the
weighing plat-
form
Latch Button
—
N
Control Panel
Q の @@ @
sem Ze
—
©
Controls
On/Off Turns Scale on or off. (If operating on
batteries, Scale turns off automatically 3 min-
utes after weighing.)
Zero Press to cancel out (tare out) weight of
any objects on the platform before placing
child on platform.
Kg/Lb Press to convert pounds-ounces to
kilograms and vice versa.
Average/Unlock Press to get a four-second
average ofa moving child's weight . The weight
will lock into the display. Press again to un-
lock display.
Recall Press to display thelastlocked weight.
NOTE: Recall only operates when the Scale is
turned off.
©, ox à
Status Lights
Locked (Green) Child’s average weight is
locked on display. Displayed weight value will
not change, even if child is removed from
Scale.
Averaging (Yellow) Scale is computing a -
four-second average of child's weight. Do not
touch child while Averaginglight is flashing or
weighing error will result.
(8) Overload Signal Will come on when weight
on platform exceds 55 lbs (25 Kg).
Lo Bat Signal Will come on when approxi-
mately one-half hour of battery life remains.
Charging Comes onwhen batteries are charg-
ing (whenever Scale is connected to wall out-
let).
SS50-N1-220V(B09)
OLYMPIC SMART SCALE,
一 一 、

Operation—AC or Battery
| 7 The following instructions apply whether Smart Scale is
operating connected to a wall outlet or operating on its
rechargeable batteries.
NOTE: The Scale can be used for weighing while the
batteries are recharging or even if the batteries have been
removed.
To Turn On/ Off
‘Press the On/Off button on the front panel. Wait until a
series of walking dashes go across the display. When the
zero weight reading appears, the Scale has automatically
found its zero reference point. The Scale is adjusted at the
factory to power-up in the Pounds-Ounces mode. See page
4-2 to change power-up mode to kilograms.
Note: Weight ofblankets orany other objects placed on the
platform before the zero reading appears will be automati-
cally cancelled.
Adjusting Platform Ends
© Hold the platform end and press the large red button (Fig.
2-2) to release the platform ends. Lower the end.
Toretum an end to the full-up position, lift the end until
it locks into place. The word LATCHED will appear in the
button’s rim (Fig. 2-3).
Either one or both ends can be lowered to accommodate
the child being weighed. Whenever possible, both ends
should remain up to safely hold the child.
CAUTION: Ends should only be placed in the full-down
or full-up position. Ends lock only in the full-up
position when LATCHED appears on the red button
rim.
CAUTION: Do not allow child to sit or stand on the
ends.
Weighing Child
After zero weight appears, place child in platform.
Child Not Moving
If the child is not moving, read and record the “live” weight
displayed.
Child Moving
If the display is changing too rapidly to get an accurate.
“live” weight, press the Average/Unlock button. The
yellow Averaging light starts blinking while the Smart
Scale takes a four-second average of the child’s weight. At
the end of the averaging cycle, the green Locked light will
come on. Read and record the displayed weight.
CAUTION: Touching the platform or child while the
Averaging light is blinking can result in an incorrect
weight. If that happens during weighing, see below.
Weight Lock/Unlock
Weight remains on display until Average /Unlock button is
pressed to unlock the display. If the Scale is turned off
while the display is locked, it will re-zero itself when the
Scale is turned back on.
Note: Make sure zero weightis not accidentally locked into
the display. When display shows zero weight, the green
Read light must be off. If the Read light is on, press
Average/Unlock.
If scale is touched during averaging:
1. Wait for the Locked light to come on.
2. Press Average/Unlock to unlock the display.
3. Press Average/Unlock again.
Recalling Last Locked Weight
If Smart Scale is turned off or loses power, the last locked ©
in weight can still be recalied by pressing Recall button.
With power off, press Recall button. Scale display will
come on and display the last locked weight for 10 seconds
then turn off.
Note: Recall button works only when power is off.
To Weigh Next Child
If the display is locked’ (green Read light is on), press
Average/Unlock button. Scale reads zero. If not, press
Zero button.
Hold end while
6
/
Push to release end
LATCHED
Fig. 2-2 Lowering Scale Sides
SS50-N1-220V(B09)
Fig. 2-3 Latch Button Rim
| Page 22

Pounds-Ounces to Kilograms
_ When first turned on the Scale reads in pounds-ounces,
down to one ounce. To display weight in kilograms (kg)
press the Kg/Lb button. Kilograms are displayed to 0.02 kg.
To return the display to Pounds-Ounces, press the button
again.
Display Resolution
Internally, the Scale is measuring weight to the nearest 2.5
grams. In the kilogram mode, it is rounding the displayed
weight to the nearest 20 grams. In the pounds-ounces
mode, the weight is rounded to the nearest 28 grams
before it is displayed in pounds-ounces. A manual conver-
sion from the pounds-ounces display to kilograms may not
match the Scales's kilogram display reading. This is due
only to display resolution. The kilogram weight display is
correct.
Cancelling Weight of Objects on
Platform
There are two ways to cancel (tare out) the weight of
blankets or other objects:
- Scale on Place blanket on platform and press Zero
button. Weight of blanket will be cancelled out and
display will read zero.
- Scale off Place blanket on platform prior to turning on.
Press On/Off, when zero appears, blanket's weight has
been automatically cancelled out.
Note: If blanket is removed from platform after its weight
has been cancelled out, the Scale will display negative
weight. Press Zero again to re-zero the Scale.
Overload
If the load exceeds 55 pounds (25 kg), the Overload signal
on the display will come on. Reduce the weight on the Scale
platform.
Cleaning
Smart Scale can be wiped clean with a cloth dampened
with an common hospital disinfectant.
Note: Do not spill any liquid on the Scale as it might enter
the case and damage the electronics.
Page 2-3
Battery Operation
When using the Scale on batteries, wrap the power cord DN
around the cord cleats on the back (Fig. 2-4).
Charging
The Smart Scale has internal rechargeable batteries which
are automatically charged (Charging Signal comes on)
whenever the Scale is connected to a wall outlet. Approxi-
mately 14 to 16 hours are required to fully charge batter-
ies. Batteries can be continuously charged without dam-
age.
The Scale can be used while the batteries are charging.
Charge Life
When fully charged, the Scale will operate for approxi-
mately three hours of continuous use or 50 weighings.
Low Battery
When approximately one-half hour of battery life remains,
the Lo Bat signal will come on. Connect the Scale to wall
‘outlet as soon as convenient.
If Lo Bat signal begins blinking, it indicates the battery
charge has been depleted. The Scale will shut itself off
automatically. It should be connected to a wall outlet for
recharging or use.
Battery Replacement
See Service Section
Wrap power cord here
Fig. 2-4 Cord Cleats
SS50-N1-220V(B09)

Section Three
Installation OLYMPIC
SMART SCALE,
Smart Scale is shipped fully assembled.
Display Protective Cover
Prior to first use, remove and discard the green protectiv
cover over the display.
Stationary Use
Place Scale on flat, level table or counter surface. Make
sure that Scale cannot slide or "walk" off the edge. Weight
of Scale is approximately 57 pounds.
Portable Use
If the Scale is to be used on a cart, it is recommended that
it be bolted to the cart using the four 10-32 UNF threaded
mounting holes in the bottom of the Scale (Fig. 3-1)
CAUTION: Make sure that cart, with Scale mounted; is
stable and will not tip over with added weight of patient
(up to 55 pounds).
AN
Threaded holes for
mounting on cart.
Fig. 3-1 Cart Mounting Holes
SS50-N1-220V(B09)
Model 50
When inserted through bottom of shelf, mounting screws
must project no more that 1" above top ofshelf. Otherwise,
they will damage the load cell when they are inserted into
the Scale.
Electrical Requirements
220/240 VAC, 50/60 Hz, 0.06 Amperes
CAUTION: Use hospital-grade outlet only. Do not use
adapters or extension cords.
Initial Battery Charge
Smart Scale has internal rechargeable batteries which will
be automatically charged when the Scale is connect to a
wall outlet.
The initial battery charge requires 14 to 16 hours to reach
full charge. The Scale can be used while batteries are
charging.
Carrying Scale
To pick up the Scale, grasp firmly at the bottom. Never
attempt to lift Scale by sides. Two people should lift Scale
as it weighs approximately 57 pounds.
Calibration Check
Every Smart Scale is calibrated at the Olympic Medical
factory before shipment. However, calibration of the Scale
should be checked before it is put into use. (See "Calibra-
tion“ under Service Section of this manual.)
Page 3-1A

Section Four
Service
Replacing Batteries
1. Disconnect Smart Scale from wall outlet.
2. Ensure Scale is turned off.
3. The battery cover is located at the back of the Scale.
4. Loosen the two screws holding the cover in place (Fig.
4-1).
5. Remove the cover.
6. Remove the batteries and replace with six, size C,
rechargeable Ni-Cad batteries. Replace all six batteries at
the same time. Observe battery polarity.
7. Replace the battery cover and install the two screws
holding it in place.
Replacing Fuses
Fuses are located on the back side of Scale (Fig. 3-1).
There are two fuses:
1. For AC power: 1/8 amp, 250 V, fast acting.
2. For batteries: 1 amp, 250 V, fast acting.
Replace as required.
Calibration
Rationale
As with any precision electronic instrument, the Smart
Scale can drift out of calibration over time. Since no
electronic scale recalibrates itself automatically, the only
way to assure correct recalibration is to place an accurate,
known weight on the scale and make the required internal
adjustments so that the scale displays the correct weight.
Calibration Weights
The Model 50 calibration procedure requires two precision
weights, Cat. No. 56357. Together the two weights weigh
12.5 kg.
Model 50
Calibration Upon Receipt
The Scale was calibrated at our factory in Seattle prior to
shipment. However, it should be recalibrated before being
put into use because local variations in the force of gravity
can affect weight by as much as 20 grams.
Calibration Frequency
Scale calibration should be checked every month for the
first year. Then the frequency can be adjusted based on
how far the Scale readings have drifted. If it is staying
within 20-40 grams, reduce the calibration frequency to
every 12 months. For larger drifts, increase the frequency
to every 3 months. If the drift is very large, check the
Troubleshooting section. |
To begin, place the Scale on a firm, level surface. Ambient
temperature should be between 70° and 75°F, normal
room temperature.
Calibration Switch Access
The calibration switch access panel is located on the front
panel under the controls (Fig. 4-2).
1. Remove the two screws holding the cover in place to
expose the calibration switches.
2. Push Calib switch, S1-2 (Fig. 4-3), up.
Procedure
Turn the Scale on. The display should read “SCALE
CALIb.” If not, make sure the calib switch is up.
1. Turn the Scale on. Exercise the load cells by placing the
two calibration weights in the center of the platform for 10
seconds. Then remove the weight for ten seconds. Repeat
three times.
2. Place the 12.5 kg calibration weights in the center of the *
platform.
3. Adjust the Coarse Zero pot (Fig. 4-3) until the display
reads 16,384 130.
Coarse Zero, R5
Fine Zero, R6
Coarse Span, R7
Fine Span, R8
\ wend-to-end Balance, R9
eee FE
Memory Bank Select, S1-1
Battery Compartment
Cover .
Access Panel
Display Test, S1-3 “
7 = | Calibration Mode, s1-2/ //
Date Code, S1-4
Fig. 4-1 Battery Cover (on back of
Scale)
Page 4-1
Fig. 4-2 Calibration Switch Access
Panel
Fig. 4-3 Calibration Switches
SS50-N 1-220V(B09)
OLYMPIC SMART SCALE, —

4, Adjust the Fine Zero pot until thedisplayreads. 16,384.
Note: Due to electronic noise, the display will jitter +2. This
is normal.
5. Momentarily press Zero button. The display will read 0
+2.
6. Remove the calibration weights.
7. Adjust the Coarse Span pot (Fig. 4-3) until the display
reads -5000 +30.
8. Adjust the Fine Span pot (Fig. 4-3) until the display
reads -5000 +2.
9. Press Zero. The display should show 11,384. If not,
repeat steps 2 thru 8. If the Scale will not calibrate, contact
the Olympic Medical Service Department toll free number
1 800 426-0353.
10. Press Calib switch off, (Fig. 4-2), down.
11. Replace Calibration hatch cover.
Changing Power-Up Display
Smart Scale is pre-set to power up in the pounds-ounces
mode. To have it power up in the kilograms mode:
1. Disconnect the power cord from the wall outlet.
2. Remove the two screws holding the calibration switch
panel (Fig. 4-2).
3. Push switch S1-1 down.
4. Replace access cover.
Specifications
Accuracy (Nominal): + 0.02 kg (102)
Capacity: 25 kg (55 Ib)
Resolution: 0.02 kg (1 oz)
Scale Weight: 57 ib.
Scale Dimensions:
Sides Up: 28"W x 22"D x 10"H
Sides Down: 38.3"W x 22"d x 10"H
Power Reguirements:
220/240 VAC, 50/60 Hz, 10 W
Battery Reguirements:
Six, C-size, NiCad, rechargeable
Troubleshooting
The Olympic Smart Scale, Model 50, can be field serviced
to the printed circuit board (PCB) level. The faulty board
mustbe returned t to Olympic Medical for repair or replace-
ment.
Inorder to identify the problem, please follow the Trouble-
shooting and Theory of Operation sections carefully.
-SS50-N1-220V(B09)
Troubleshooting requires the weighing platform be re-
moved to expose the test points on the scale's main printed
circuit board (Fig. 4-7).
Prior to performing any troubleshooting, read the Smart
Scale Theory of Operation, page 4-7. This provides an
overview of how the Scale circuits operate
CAUTION: Only hospital-qualified personnel should
perform internal servicing. Electrical shock hazard
when circuits are exposed.
Static and Contamination
The integrated circuits and semiconductors on the PCB’s
can be damaged by electrostatic discharge or by body oil
contamination and fluids such as disinfectants. Always
observe proper handling precautions (below) at all times.
« Minimize handling of circuit boards.
- Discharge personal static by touching grounded metal or
by wearing a. grounded wrist strap, before touching
parts.
- Keep replacement boards in their anti-static bags until
ready to use.
- Avoid touching pins or traces. Handle PCBs by edges to
avoid static discharge and avoid contamination by oil
from fingers.
ㆍ Avoid plastic, vinyl and styrofoam in the work area.
- Avoid wearing clothing which may pick up static elec-
tricity.
- Do not slide PCBs or components over any surface.
| Troubleshooting Hints
CAUTION: Operate Scale in the battery mode, when
possible, to avoid electric shock.
- Analyze symptoms BEFORE disassembly and trouble-
shooting. Read the Theory of Operation section to
understand the system. Formulate a theory ofa possible
cause for the symptom and make tests to check the
theory.
- Check the easiest and most obvious possible problems
first (such as fuses, mechanical interference, dead bat-
teries, etc.).
- Study the specifications and user's instructions, par-
ticularly the front panel switch logic to be sure that the
Scale is behaving abnormally. In some situations cer-
tain switches normally do not work. For example, Zero
will not work if display is locked. Recall will only work if
the Scale is off.
- Perform-a-thorough visual inspection... All connectors
and cables should be connected and secure. Check for
chafed or pinched wires. Check for signs of overheated
components. Check that all socketed parts are firmly
seated in their sockets. Check for interference with load
Page 4-2

cell movement such as wires or mechanical binding.
- Take measurements with respect to signal ground, TP10.
Troubleshoot the Scale using the test points on the Main
Board. The test points are in numerical order from left
to right on the front of the Main Board. Their function is
summarized in the table, Fig. 4-10.
- Operate Scale both on batteries and AC to see ifsymptom
is the same.
Dissasembly
1. Turn off the Scale and unplug from the wall outlet.
2. Slide one end of the Scale so it overhangs the table (Fig.
4-4).
3. Unscrew the four socket head cap screws through the
holes in the chassis (Fig. 4-5). Repeat for the other end.
4. Lift the platform assembly up to expose the weighing
platform (Fig. 4-6).
Note: The platform assembly, with its hinged ends, is not
field repairable and should not be disassembled. If it is
damaged it should be returned to Olympic Medical for
repair or replacement.
The Main Board test points are now exposed (Fig. 4-7).
Removing Weighing Platform
It is not necessary to remove the weighing platform unless
the main printed circuit board must be removed.
1. Remove the two socket head cap screws and the two flat
head cap screws (Fig. 4-8).
2. Lift the weighing platform off. Take care not to lose the
spacer (Fig. 4-9).
Removing Main Board
1. Disconnect all connectors: Transformer, Load Cells,
Battery and Display Board.
2. Remove the mounting screws holding the board in
.place.
3. To replace the board reverse the above steps.
Reassembly
Reassemble the Smart Scale by reversing the dissassembly
steps.
When installing weighing platform, the two socket head
cap screws (Fig. 4-8) require 90 in-ib torque. The two flat
head cap screws need only to be tight.
Fig. 4-5 Cap Screws
Fig. 4-6 Removing Platform
Page 4-3
Fig. 4-7 Test Points On Main Board
SS50-N1-220V(B09)

The cap screws attaching the main platform to the chassis
(Fig. 4-5) require 4-6 in-lb torque.
' Note: When reinstalling the weighing platform, ensure the
channel connected to the right load cell is square and the
swing arms move freely.
CAUTION: The Smart Scale must be recalibrated when-
ever is has been disassembled and reassembled. See
page 4-1
Symptoms and Suggested Tests
For Test Point voltage values, refer to the Test Point Chart
in Fig.4-10.
Scale will not come on and Zero:
1. If walking dashes are displayed, there are two possible
causes: .
a. The signal is beyond the zero capture range. This
could be caused by a bad load cell or a power problem.
Remove the main platform assembly (in disassembly pro-
cedure) so the aluminum platform is exposed. This will
also expose the front edge of the Main Board with its test
points (Fig. 4-10).
Spacer
- Check power voltages at test points TP3, TP5 and TP11
{with respect to ground, TP10).
- Check that the zero offset voltage is correct at TP1.
Typical value with the main platform assembly removed
will be around -1.2 volts.
- Check that the signal atTP2 is correct. Typical value with
the main platform assembly removed will be about -1.1
volts but the A/D should be able to capture anything
between -2.00 volts and +2.00 volts.
- Check that the A/D reference voltage at TP6 is correct—
around 1.00 volts.
b. The signal is too unstable to acquire zero. This could
also be caused by a power problem.
Check the +5Va and the -5Va at test points with a scope
and verify that there is no excessive noise on these lines.
If voltages are correct, check noise on the signal at TP2.
Test Point Description
TP1 Zero offset. -1.2 volts with platform ass'y. off
TP2 Analog signal input from amps to filter & A/D
TP3 +5 Va Analog +5 volts for load cells, amps, A/D
TP4 Chopper clock
TPS -5 Va Analog -5 volts for amps & A/D
TP6 A/D ref voltage. 1.00 volts normal
TP7 Vin (Battery voltage) or +11.25 Vdc if on AC.
TP8 Not very low battery signal
TP9 Not low battery signal
TP10 Ground
TP11 +5 Vd Digital +5 volts for pC, displays, etc.
TP12 =| Not On/Off switch signal input
TP13 Not Recall switch signal input
Fig. 4-9 Weighing Platform Spacer
SS50-N1-220V(B09)
Fig. 4-10 Test Point Voltages
Page4-4

2. Ifthe walking dashes do not appear, and the On/Off
switch is ineffective: Listen for the reed relay clicking (to
turn on the DC power). If clicking cannot be heard then
check the fuses on the back. One fuse is for batteries and
the other is for AC.
Ifthe relay clicks, then the appropriate fuse is functioning.
Then check to determine that the Scale stays on. This can
best be verified by observing the LED, DS1, on the right
front of the Main Board (Fig. 4-11).
The main platform assembly must be removed. DS1
indicates that +5Vd is present.
If DS1 does not come on (even momentarily) then check
connectors from the membrane panel to the Display Card
to the Main Board.
Pressing the On/Off switch should make TP12 on the Main
Board go low. Ifthereis no voltage ofany kind at TP12 then
check that connector P1 from the transformer is connected
to J1 on back of the Main Board.
Also verify that connector P2 is connected to J2 when on
batteries. The aluminum sub-platform must be removed
to inspect these connectors. Also verify voltage at TP7. Try
on both AC and batteries.
If DS1 comes on but no walking dashes appear, it
indicates that the uC is not working. Verify that the
jumpers near the pC (U12) are correct. JP2 should have
a jumper at A and JP3 should have one at B. Also verify
that the EPROM, U13, is properly seated in its socket. The
I/O expander, U15, is also suspect at this point.
If the On/Off switch signal is at TP12 and DS] lights but
‘does not remain lit when On/Off is released, check relay
KI. The pC, EPROM, I/O expander and jumpers are
suspect again (previous paragraph).
IfDS1
won't illuminate, verify voltage at TP7. It should be
about +11.25 V ifon AC and 6 to 8 volts if on batteries.
If proper voltage is present at TP7 and a low (below 0.5V)
voltage reading comes in on TP12 when On/Off switch is
activated, but DS1 still won’t come on, then the On/Off
latching circuit is bad and the Main Board must be
replaced.
If the voltage is not at TP7, check the AC input through F1,
filter FL1 to primary of Tl. T1 secondary voltage coming
into J1 (pins 1 and 3) should be about 19.9 Vac (with Scale
off; no load). Voltage across the large electrolytic capacitor,
C43 should be about 26 Vdc (no load).
Scale will not lock:
Pressing Lock/Unlock should provide a low to pin 16 of
U15 on the Main Board. Ifnot, check membrane switch on
front panel and connectors down to the Main Board. If pin
16 of U15 is receiving the signal but the Lock/Unlock |
function is still inoperative, replace the Main Board.
Scale will not change units:
Pressing the Kg/Lb switch should provide a low to pin 23
of U15 on Main Board. If not, check membrane switch on
Page 4-5
front panel and connectors on the Display Card down to
the Main Board. If pin 23 of U15 is receiving t the signal,
replace Main Board.
Scale will not zero with Zero button:
Pressing Zero should provide a low on pin 1 of U15 on Main
Board. If not, check membrane switch and connectors on
the Display Card to the Main Board. If signal is OK, but
Scale
still shows no response to the Zero button, replace
Main Board.
Recall switch will not turn on the Scale:
Pressing Recall should provide alow at TP13. Ifit does not,
then check the connectors from the membrane front panel
to the connectors on the Display Card and to the Main
Board.
Ifa lowis seen at TP13 when the Recall switch is activated,
but the Scale will still not turn on and show last locked
weight for 10 seconds, then the On/off latch circuit is
suspect. Replace Main Board.
Recall switch activates the display but the Scale shows
the incorrect weight (e.g. 0.00 Kg):
Check that the non-volatile ram, U16, is plugged in. U16
has a small internal battery which may go dead after many
years. Olympic Medical guarantees the battery for 10
years.
Some segments or annunciator lights do not come on:
Turn on the Scale with the On/Off switch while holding
either the Lock/Unlock, Zero or Kg/Lb switch. This turns
on all segments and lights. If all LEDs do not light, either
replace the Display Card or purchase new displays from
Olympic Medical. Replace all six whenever one fails. This
will ensure digits have the same brightness.
Scale will not weigh accurately:
The load cells are suspect. Slight linearity errors (exceed-
ing specifications) or off-center load errors can be caused
by a defective load cell. However, other factors could cause
errors. Check-that nothing (cables, etc.) is touching or
rubbing on platform. All weight must go through the load
cells. Also check that the ends are not binding on the right
load cell.
If the percent error is constant throughout the range,
recalibrate. If errors are random or there is a linearity
problem, calibration will not work.
Check power supply voltages. If voltages are correct,
weighing inaccuracy or drift can be caused by a defective
load cell or the analog circuitry on the Main Board. The
load cell connectors are also suspect. Return Scale to
Olympic Medical for analysis.
Scale drifts;
Drift can be caused by moisture, contamination, a bad
connection or a bad lead cell. Return the Scale to Olympic
Medical for repair.
SS50-N1-220V(B09)

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Fig. 4-11 Main Board Assembly
Page 4-6

Theory of Operation
General Overview
Fig. 4-12 is a simplified block diagram tht illustrates the
essential components of an electronic scale. A weight
sensing device translates a force into an electrical signal.
This analog signal is amplified and translated into a digital
signal for a microcomputer (jC). The uC takes this raw
weight data (usually binary) and performs manipulations
to present it in readable form on a display.
Load cells are used as the weight sensing devices in the
Olympic Pediatric Scale. A load cell contains four strain
gauges connected to form a Wheatstone Bridge (Fig. 4-13).
If an excitation voltage is applied in two opposite corners
of the bridge, a small differential signal occurs at the other
two corners. This signal will be proportional to the applied
weight. The signal is also proportional to the excitation
voltage.
The Pediatric Scale employs “ratiometric” operation. Ifa
small change in excitation voltage occurs causing a signal
change, the gain and zero circuits change in the opposite
direction to counteract the original change.
Pediatric Scale Overview
Refer to the block diagram in Fig. 4-14. The Scale has two
printed circuit boards: the Main Board and the Display
Card. Components are mounted on the chassis. The front
panel has five membrane switches.
Power Supply
Line power is connected through a fuse and RFI filter to the
primary of the power transformer. The secondary AC is
rectified and filtered on the Main Board. The DC is
regulated by a +12 V regulator which provides all current
to the Scale.
The +12 V from the regulator supplies the charging circuit
for the nickel-cadmium batteries. It also provides a signal
indicating to the computer that alternating current (AC) is
present. The +12 Volts are also applied to the on/off latch
circuit. The On/Off membrane switch on the front panel
controls the on/off latching circuit.
Each time the On/Off switch is activated, this circuit
alternately turns a reed relay on and off which controls DC
power to the Scale. The Recall switch can also turn the
Scale on but it cannot turn the latch off.
The power supply has a +5 V regulator for digital power
and another +5 V regulator for analog power. A switching
regulator provides negative voltage to an op-amp which
provides -5 V analog voltage which tracks the +5 V analog
voltage. Separate digital and analog grounds are used.
Signal Flow
Refer to the Block Diagram, Fig. 4-14. The weight on the
platform is sensed by the load cells. The signal from the
load cells is amplified by a chopper stabilized instrumen-
tation amplifier.
The zero control provides ratiometric zero offset to cancel
the tray weight and load cell offset, and provide DC offset
for the A/D converter. Either of two filters can be selected
by the pc.
Firsta light filter is used because it allows rapid acquisition
of the weight data. The nC switches to the heavier filter
when in the Averaging mode. (The pC also performs
software averaging to get the best possible approximation
of the weight.)
The span (gain) control is also ratiometric and controls the
gain of the A/D.
The A/D provides binary data to the pC. An external
EPROM is used to store the software. An I/O expander
receives inputs from the Zero, Lb/Kg and Lock/Unlock
switches on the front panel. Since both the On/Off switch
and the Recall switch tum on the Scale in hardware, the
uC must determine which switch turned it on. Therefore,
these switches are also indirectly tied to the pC. There are
two serial data outputs to display drivers on the Display
Card.
CO pis ==
+ SIGNAL
- SIGNAL
Fig. 4-12 Essential Scale Components
Page 4-7
Fig. 4-13 Wheatstone Bridge
SS50-N1-220V(B09)

Detailed Circuit Description
Load Cells
The wiring diagram, Fig. 4-15, shows the load cell connec-
tions. Inside the load cells there are temperature com-
pensation networks which are not shown.
The capacity of the Scale is 25 kilograms. The sensitivity
ofeach load cellis 2mV per volt at 30 kg. The output signal
of one separate load cell is 2mV per volt of excitation at 30
kg.
The load cells are connected in parallel through a balanc-
ing pot, R9. The net effect is an output of 148.5 nV per
gram (with 5.0 Volts excitation). Since this is such a small
signal, a very stable amplifier is needed.
1
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Instrumentation Amplifier
Refer to the Main Board schematics, Fig. 4-16, 4-17 and
4-18.
U7 and U8 form a differential chopper stabilized instru-
mentation amplifier. The gain is fixed by R18, R19 and R20
at 328.3. These are special precision resistors whose
temperature coefficients are matched to within 3 parts per
million per degree C. The input to the amplifier is guarded
at the common mode voltage of about +2.5 V provided by
US.
U4 is a high accuracy unity gain amplifier. It changes the
differential input to a single ended output. Italso sums in
the zero offset voltage. Zero offset is provided from R5, R6
and U1. A copper electrostatic shield is situated over this
very sensitive analog section. The signal from U4 output
is fed through either filter to the input of the A/D converter,
U11. Analog switches of 010 are used to select the
appropriate filter.
Fig. 4-14 Detailed Block Diagram
SS50-N1-220V(B09)
Page 4-8

Analog to Digital Converter
Refer to the Main Board schematics, Figs. 4-16, 4-17 and
4-18.
Ull, the A/D converter, is an integrating, charge balanc-
ing type. Each conversion cycle takes about 400 msec. It
has a dynamic range of + 32,768 counts (15 bits plus sign;
a total of 65,536 counts). The input signal to the A/D is
about 48.82 HV per gram.
The system is designed to internally resolve 1.25 grams for
each count of the A/D (0.8 counts/gram).
The gain of the A/D (and the system) is controlled by R7
and R8 which provide its reference voltage. This reference
voltage should be 1/2 of the A/D range of + 32,768 counts
or:
1x 48.82uV x 1.25g x 32,768cnt = 1.000 V (Typ at TP3)
2 g cnt
This may vary depending on the exact sensitivity of the
load cells,
This is fully ratiometric. For example, ifthe +5 V excitation
to the load cells decreases slightly, then the load cells’
signal decreases proportionately for the same weight;
however, the A/D reference voltage will also decrease
thereby increasing the A/D’s sensitivity (gain). The result-
ant digital output will remain the same.
To utilize the full range of the A/D, the system’s zero offset
is such that 12.50 kg gives a zero input voltage to the
A/D. 25.00 kg will equal +0.610 volts and zero kg equals
-0.610 volts. These voltages can be measured at TP2.
NOTE: The zero offset voltage at TP1 will be lower than
-0.610 V because it must also cancel out the weight of the
platform. Voltage at TP1 is around -1.17 volts. This may
vary somewhat depending on the exact weight of the
scale’s platform and the particular degree of zero offset of
the load cells.
The pC monitors the Data Valid line and, when valid, reads
the A/D binary output. The A/D presents the high order
bits or low order bits depending on the request by the pC
via the High Byte or Low Byte Enable lines.
Note : All voltages given are nominal. Each system will
vary depending on its specific load cell sensitivity, zero
ofíset and tray weight.
Microcomputer
Refer to the Main Board schematic, Fig. 4-18.
The microcomputer, Ul2, is an 80C39, a member of the
8048 family. It has RAM inside and uses an external
EPROM, U13. U15 is an input/output expander. The
function of the pC is controlled by firmware (software). The
software occupies 4K bytes of the EPROM.
Page 4-9
Software overview
The computer performs housekeeping chores such as
initialization to thePound-Ounce modeand auto-zeroupon '
power up. It performs zero tracking for slow shifts less
than +10 grams.
If weight is applied, it computes weight in proper units.
Also, it performs averaging and locks the best approxima-
tion of the weight on the display if requested by the Lock/
Unlock button.
The last locked weightis stored in the non-volatile external
RAM. This data is retrieved in the Recall mode. The non-
volatile RAM has a serial interface.
The front panel switches are continually scanned. The pC ㆍ
interfaces to the A/D directly but otherwise interfacing is
done by U15.
Data is clocked to each of the two display drivers (on the
Display Card) serially with a common clock. The pC does
7 segment decoding and formatting to illuminate the
correct segments and annunciators.
The quad DIP switch, S1 in Fig. 4-3, can be used to aid in
trouble-shooting and calibration. S1-1 is the Memory
Bank Select switch. It can select either the upper 4K or
lower 4K bytes of the EPROM.
If S1-1 is up, the Scale powers up in thePounds-Ounces
mode. IfS1-1 is down, the Scale powers up in theKilograms
mode. Otherwise, the code in both sides of the EPROM is
identical.
As mentioned, the A/D has 1.25 gm/count internal reso-
lution. However, due to noise, the A/D data is divided by ^
2 by the pC to give an actual internal resolution of 2.5
grams per count.
If S1-2 is turned on, the display will show these counts
from O to 32,768. The system is biased (with the zero
adjustment) so that 11,384 counts is zero weight (that will
be a signal voltage of about -0.610 volts at TP2, Fig. 8).
12.50 Kg will be a reading of 16,384 counts (a signal
voltage of 0 volts) and 25.00 Kg will give a reading of 21,384 ”
counts (a signal input of +0.610 volts). *
Voltages will vary depending on the specific sensitivity of
individual load cells and whether the system is calibrated.
In the calibration mode, the Zero button alternately zeros
and unzeros the display.
Ifthe display test switch, 5 1-3, is activated (prior to power-
up), then a display test routine is activated which shows
segments and annunciators sequentially and then turns
them all on. This is convenient for verifying that no
segments are open or shorted to another segment. Also, it
is used to adjust the segment brightness.
Ifthe Scale is turned on with the On/Off switch while either
the Zero, Lb/Kg, or Lock/Unlock switch are also held
down, then all segments and annunciators light up (re-
gardless of what dip switches are activated) until the:
switches are released.
SS50-N1-220V(B09)

S1-4 is the date code switch. This switch causes the
display to show the last software revision date in the format
MM.DD.YY. Always return S1, 2, 3 and 4 to off before
returning the Scale to nursery service.
Display
Refer to Display Card schematic, Fig. 4-19.
Data is clocked serially into two display drivers with a
common clock. The format is one start bit followed by 35
data bits. On the 36th clock, all 35 data bits are automati-
cally latched to the outputs of the display drivers.
Each driver has a brightness control, Rl & R2. Current of
a group of lit segments can be measured at El. High
efficiency 7 segment displays are used. This allows
uniform segment brightness at only 4.8 mA per segment.
Ifa display segment burns out, replace all six displays to
retain uniform brightness. To avoid heat build-up in the
power supply, never set segment current above 4.8 mA/
segment.
Power Supply
Refer to Wiring Diagram, Fig. 4-15 and Main Board Sche-
matic, Fig. 4-16.
Alternating current power from the power cord comes into
the chassis. The chassis has F1, a 1/4 amp, normal-blow
fuse, a filter and a transformer (F1 is 1/8 amp for 220 Vac
units).
The secondary of the transformer T1 is connected to the
Main Board through Pi-J1. CR3 through CR6 forms a full
wave bridge rectifier. CR2 is a transient voltage suppres-
sor, and C43 and C44 provide filtering.
VR2 is a +12V voltage regulator. All Scale current comes
through VR2. All these circuits are live when the Scale is
plugged in, whether it is on or off.
When the Scale is off and the front panel On/Off switch (or
the Recall switch) is pressed, Q7 is biased on, supplying
SS50-N1-220V(B09)
power to U17. U17, a switch debouncer, provides some
delay and toggles flip-flop, U18, on. This turns on Q8
which energizes relay K1.
When the On/Off switch is released, Q7 turns off, but now
Kl’s-contacts supply power to keep itself and everything
else on.
To turn off the Scale, the On/Off switch is pressed again.
Q7 turns on and a signal goes through U17 which toggles
U18 off and turns off K1. The Scale is still on due to Q7,
but when the On/Off switch is released, Q7 turns off and
the Scale is off.
The Recall switch cannot tum the scale off. The pC can
toggle U18 off (independently of the On/Off switch) by -
applying a low directly to pin 3 of U18. The On/Off switch
(or Recall switch) must be held for at least 1/5 second for
the piC to recognize it.
If the switch is hit very quickly and let go, then the pC will
not know whether the On/Off switch or the Recall switch
was hit, and the pC will turn the Scale off. This is normal.
The pC will turn the Scale off after 10 seconds of recall or
when the very low battery threshhold is reached.
Voltage regulator, VR3, provides digital +5 volts. DSl, a
small LED situated on the Main Board, shows when the
Scale is on. U2, a switching regulator, provides a negative
voltage. VR1 provides a regulated +5 V for the analog
circuitry. The negative voltage from U2 is applied to U5
which has a gain of -1. This inverts the +5 V analog toa
tracking -5 V analog voltage.
Low battery voltage and very low battery voltage is detected
by U6 and U3 respectively. Threshold adjustments are set
by R31 and R27 respectively.
Front Panel The front panel contains five membrane
switches. Each switch, when activated, shorts the line to
ground. Membrane switches have some resistance (they
do not give a direct short). Several ground traces are used
to keep this resistance as low as possible (Typically 30Q
to 500).
Page 4-10

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SCHEMATIC, MAIN PCB - SHEET 1 of 3
PEDIATRIC SCALE
Page
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SCHEMATIC, MAIN PCB - SHEET 2 of 3
PEDIATRIC SCALE
$550-N1-220V(B09) | Page 4-14 |

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SCHEMATIC,
MAIN
PCB
-
SHEET
3
of
3
PEDIATRIC
SCALE
Page 4-15
—
SSAN-NT 9O9NT7DANO)