SR Instruments SR Scales SR241 Service manual

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 1 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
S
by S Instruments, Inc.
Operating and Service
Manual
Model
SR241/SR241SO
Portable Infant / Adult Scale

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 2 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
TABLE OF CONTENTS
TABLE OF FIGURES......................................................................................................................2
PACKING CHECKLIST –MODEL SR241..................................................................................3
PACKING CHECKLIST –MODEL SR241SO ............................................................................3
ASSEMBLY.......................................................................................................................................4
REPLACEMENT PARTS AND ACCESSORIES ........................................................................4
SYSTEM DESCRIPTION AND INTENDED USE.......................................................................4
SYSTEM DESCRIPTION AND INTENDED USE (CONT’D) ...................................................5
STORAGE.........................................................................................................................................5
CLEANING AND DISINFECTING...............................................................................................6
SPECIFICATIONS...........................................................................................................................7
BUTTON FUNCTIONS...................................................................................................................8
BASIC SYSTEM OPERATION......................................................................................................9
BATTERY REPLACEMENT.......................................................................................................10
THEORY OF OPERATION .........................................................................................................11
CALIBRATION..............................................................................................................................12
TROUBLESHOOTING.................................................................................................................12
WARRANTY...................................................................................................................................13
TABLE OF FIGURES
Figure 1: Optional Soft-Sided Carry Case ...................................................................................5
Figure 2: SR241/SR241SO Label ..................................................................................................8
Figure 3: SR241/SR241SO Battery Compartment....................................................................10

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 3 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
PACKING CHECKLIST –Model SR241
Portable Infant / Adult Scale
PACKING CHECKLIST –Model SR241SO
Portable Scale

DESCRIPTION
QUANTITY
SCALE BASE
1 ea
INFANT CRADLE
1 ea
9 VOLT BATTERY
1 ea
CERTIFICATE OF CALIBRATION
1 ea
MANUAL
1 ea
OPTIONAL ITEMS IF ORDERED
SOFT-SIDED CARRY CASE
1 ea

DESCRIPTION
QUANTITY
SCALE BASE
1 ea
9 VOLT BATTERY
1 ea
CERTIFICATE OF CALIBRATION
1 ea
MANUAL
1 ea
OPTIONAL ITEMS IF ORDERED
SOFT-SIDED CARRY CASE
1 ea

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 4 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
ASSEMBLY
STEP 1: Unpack the scale system and check parts against the PACKING CHECKLIST. If there are
any missing or damaged parts, call the Service Hotline at: 1-800-654-6360.
STEP 2: Insert the 9-volt battery. See BATTERY REPLACEMENT instructions.
STEP 3: SR241 scale system Infant Cradle slides onto the Scale Base and snaps securely into
position.
REPLACEMENT PARTS and ACCESSORIES
SYSTEM DESCRIPTION and INTENDED USE
SYSTEM DESCRIPTION
The SR241/SR241SO Portable Infant/Adult Scale employs the latest in microprocessor and load
cell technology to provide accurate and repeatable weight data. Four (4) identically matched
transducers are strategically placed to ensure an accurate representation of the patient’s weight.
The patient’s weight is displayed on an LCD screen. With a push of a button, weight data may be
viewed in either pounds or kilograms with a displayed resolution of 0.1 lb. or 0.1 kg.
Part #
Description
SM4028
REPLACEMENT INFANT CRADLE
SR241SO
SCALE ONLY
MAN241
MANUAL
PP-4022
SOFT-SIDED CARRY CASE

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 5 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
SYSTEM DESCRIPTION and INTENDED USE (Cont’d)
INTENDED USE
The SR241 Portable Infant/Adult Scale is a unique portable scale
system that offers the versatility of being able to weigh infants,
toddlers, and adults on one lightweight and weather resistant system.
Weighing in itself at a mere seven pounds, this scale is specialized
for use in pediatrician or physicians’ offices and is also perfect for
traveling nurse applications. The optional Soft-Sided Carry Case
(Figure 1) protects the scale and facilitates its portability.
The SR241 Portable Infant/Adult Scale is a preferred means of gathering
patient weight data of adults weighing up to 400 pounds (181 kilograms),
and infants to 44 pounds (20 kilograms). Load cell technology ensures accurate and repeatable weight
readings.
The SR241SO Portable Adult Scale is a unique portable scale system that is lightweight and
weather resistant. It weighs a mere four pounds. This scale is specialized for use in physicians’
offices and is also perfect for traveling nurse applications. The optional Soft-Sided Carry Case
(Figure 1) protects the scale and facilitates its portability.
The SR241SO Portable Adult Scale is a preferred means of gathering patient weight data of
patients weighing up to 400 pounds (181 kilograms). Load cell technology ensures accurate and
repeatable weight readings.
Please heed the following warning to avoid injury to the patient or attendant.
STORAGE
STORAGE
If storing this equipment for periods longer than three (3) months, remove the battery. To
maintain proper operation of this instrumentation, storage and transport conditions should not vary
outside the following conditions: Relative Humidity 0% to 85%, Ambient Temperature 14F to
122F (-10C to +50C).
Figure 1: Optional Soft-Sided
Carry Case
WARNING
DO NOT EXCEED
MAXIMUM WEIGHT LIMIT OF
400 LB / 181 KG
Prolonged exposure to extremes of heat or cold
can damage equipment and effect accuracy.
WARNING

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 6 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
CLEANING and DISINFECTING
CLEANING
To clean the display / user interface and other scale contact areas:
Use a soft cloth dampened with water and mild detergent to clean scale surfaces.
Wipe surface with clean soft cloth dampened with water and then dry with clean soft cloth.
Do not use abrasive materials to clean scale surface to prevent damage to the surface
finish.
Do not spray liquid directly onto scale surfaces. Use only a damp cloth.
DISINFECTION
To disinfect the display / user interface and other scale contact areas:
Use a soft cloth dampened with disinfectant or a damp disposable disinfectant cloth. Cloth
cannot be dripping wet. Follow manufacturer’s instruction on the proper use of
commercially available disinfectants.
Disinfectant solutions with 1% sodium hypochlorite or 70% isopropyl alcohol are suitable
for display / user interface and other scale contact surfaces.
After disinfecting, use a soft cloth dampened with clean water and dry with a soft clean
cloth to prevent buildup of material on scale finish.
Do not use abrasive material to disinfect / clean scale surfaces to prevent damage to the
surface finish.
Do not spray liquid directly onto scale surfaces. Use only a damp cloth.
WARNING: DO NOT SPRAY CLEANING SOLUTION OR LIQUIDS DIRECTLY
ON SURFACES TO BE CLEANED.
WARNING: EXPOSURE TO EXCESSIVE LIQUID WILL DAMAGE USER
INTERFACE KEYPAD.
WARNING: DO NOT USE PRESSURIZED WATER OR STEAM. THE SCALE
SYSTEM CONTAINS ELECTRONIC COMPONENTS THAT MAY BE
ADVERSELY AFFECTED BY EXPOSURE TO SUCH AN
ENVIRONMENT.

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 7 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
SPECIFICATIONS
MAXIMUM WEIGHT
CAPACITY
Infant: 44 lb (20 kg)
Adult: 400 lb (181 kg)
DIMENSIONS
Infant Cradle: 22 in x 12.5 in (55 cm x 32 cm)
Adult Platform: 12 in x 14 in (31 cm x 36 cm)
DISPLAY TYPE
LCD
DISPLAY RESOLUTION
Infant: ¼ oz (0.01 kg)
Adult: 0.1 lb (0.1 kg)
ACCURACY
0.2% +/- 1 digit of displayed resolution (over 0.2 kg)
AUTO ZERO
One button operation
SR241 SCALE WEIGHT
7 lb (3 kg)
SR241SO SCALE WEIGHT
4 lb (2 kg)
AUTO POWER DOWN
After 1 minute
AVERAGING
Automatic digital filter
POWER SUPPLY
9-volt battery
CALIBRATION
Calibration is traceable to NIST standards
OPERATING CONDITIONS
Normal operating conditions for this product:
Ambient Temperature Range: 68F to 85F (20C to
30C) Relative Humidity Range: 0% to 85%
Avoid exposure to high-pressure water or steam.
TRANSPORATION AND
STORAGE
Storage conditions should not vary outside the following
conditions: Relative Humidity 0% to 85%, Ambient
Temperature 14F to 122F (-10C to +50C). Remove
batteries if storing longer than three (3) months.

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 8 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
BUTTON FUNCTIONS
SYSTEM ZERO
ZERO –ADULT MODE
To zero for adult weigh: Press the large blue “ZERO” button. Display will
read “0.0”. When patient is placed onto the scale, net weight will be displayed.
ZERO –BABY MODE
To zero for infant weigh: Slide and snap the cradle into place on the scale. Place any
blankets, pads, or disposable liners being used for infant’s comfort on the cradle before
zeroing. Press the yellow “BABY MODE” button to zero the scale system. When
baby is placed on the scale, the infant’s net weight data will be displayed.
Note: When system is zeroed, memory is emptied.
LB / KG MODE BUTTONS
Press either button to switch weight display between pounds/ounces or kilograms during
the baby weighing process and press either button to switch the weight display between
pounds or kilograms during the adult weighing process.
Pressing either button after weigh process is finished and display has shut down re-
activates display and recalls last weight reading. This must be done before system is
zeroed.
Figure 2: SR241/SR241SO Label

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 9 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
BASIC SYSTEM OPERATION
ADULT WEIGH
STEP 1: Remove infant cradle from base. Place scale on hard smooth floor surface to ensure
accurate data.
STEP 2: Press the large blue “ZERO” button and wait for the display to indicate “0.0”
STEP 3: Position patient on the platform. Weight will be displayed in a few seconds.
STEP 4: To recall last weight data, press the “LB” or “KG” buttons. Note: Must be done
before “ZERO” button is pressed.
STEP 5: If more weight needs to be added at any time during the weighing process,
add weight and press the blue “ADULT WEIGH” button. This will update the net
weight on the display
BABY WEIGH –OPTION 1
STEP 1: If necessary, attach the baby cradle by sliding and snapping it into place.
STEP 2: Place the platform on a stable counter or table-top.
STEP 3: Follow the directions for ZERO-BABY MODE in the previous section.
STEP 4: When the display indicates “0.0”, you may place the baby on the scale. If the
display shuts down before weight data can be noted, press the “LB” or “KG” button to recall the
last stored weight data.
BABY WEIGH –OPTION 2
STEP 1: Remove infant cradle from base. Place scale on hard smooth floor surface to ensure
accurate data.
STEP 2: Have an adult stand on the scale holding any accessories that will be necessary
for the baby’s comfort (blanket, diaper, etc.). Press the yellow “BABY ZERO” button.
This will zero the scale system and TARE the adult’s and additional accessories weight.
STEP 3: Place the baby in the adult’s arms. The weight displayed will be the infant’s net
weight.
STEP 4: To recall last weight data, press the “LB” or “KG” buttons. Note: Must be done
before “ZERO” button is pressed.
STEP 5: If more weight needs to be added at any time during the weighing process, add
weight and press the yellow “BABY WEIGH” button. This will update the net weight on
the display

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 10 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
BATTERY REPLACEMENT
REPLACING BATTERIES
The display will read “LobAt”when battery is low and needs to
be changed.
STEP 1: (Figure 3) Turn the scale over and locate the battery
cover. Unscrew the two (2) screws.
STEP 2: Remove and replace with a 9-volt battery.
STEP 3: Press the “ZERO” button to confirm display is working.
STEP 4: Replace cover and securely tighten screws.
STEP 5: Zero the system.
Figure 3: SR241/SR241SO
Battery Compartment

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 11 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
THEORY OF OPERATION
SR Instruments patient weighing systems are digital scales. Strain-gauge force cells convert the force
of an applied weight into an analog signal. This signal is amplified by an operational amplifier and
converted to a digital signal by an analog to digital converter. The digital signal is transferred to a
micro-controller where it is filtered, converted to appropriate units, and displayed on a liquid crystal
display.
Strain-gauge force cells each contain four strain gauges mounted in a full Whetstone-bridge
configuration. These bridges convert the physical movement of the force cell, due to the applied mass
on the system, into minute changes in electrical resistance. These changes in resistance produce a
voltage difference across the Whetstone-bridge, which is amplified by the operational amplifier. The
amplifier is configured to current sum the output of each cell, with potentiometers serving to adjust the
sensitivity (voltage out per unit of weight applied) of each bridge. The offset potentiometer produces a
small current, which nulls the output of the amplifier for an unloaded system.
The output of the operational amplifier is digitized by the analog to digital converter. The converter
integrates the analog signal onto the integrating capacitor over a short interval. The integrating
capacitor is then discharged at a rate proportional to the reference voltage applied to the converter.
The residual voltage on the integrating capacitor is then multiplied by a factor and again discharged at
a rate proportional to the reference voltage. The residual voltage from this discharge is again
multiplied by a factor and again discharged. The time taken to discharge the capacitor is proportional
to the voltage from the operational amplifier, which is proportional to the applied load on the force
cells. The time is stored as a binary number in the analog to digital converter and is transferred to the
micro-controller when the conversion is complete.
The micro-controller averages and filters the digital output of the analog to digital converter, subtracts
the value saved during the system zero operation and scales the filtered output, then displays the result
on the liquid crystal display. The micro-controller performs a rolling average of data for continuous
weigh and averages the data before locking in on the reading.

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 12 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
CALIBRATION
TROUBLESHOOTING
SYMPTOM
REASON/CORRECTIVE ACTION
System fails to perform correctly
Check battery
Make sure patient is standing on two feet, is clear of
any obstacles and that nothing, including the
caregiver, is touching the patient or scale.
Set scale on smooth, hard floor surface.
Scale reads 999.9
Return to factory for repair.
For additional information or assistance, phone our Service Hotline: [phone]
or e-mail: [e-mail]
IMPORTANT
CALIBRATION CHECK Qualified service personnel only should perform this
procedure. Load cells have no user serviceable components and should not be tampered
with for any reason. Re-calibration is generally not required, but should be verified
periodically to ensure accuracy. The recommendation for calibration check is at least
once every 12 months, or as individual maintenance policy requires.

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 13 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
WARRANTY
FOUR YEAR LIMITED WARRANTY
Each Ssystem is manufactured with high quality components. SR Instruments, Inc.
warrants that all new equipment purchased will be free from defects in material or workmanship,
under normal use and service, for a period of four (4) years from the date of purchase by the
original purchaser. Normal wear and tear, injury by natural forces, user neglect, and purposeful
destruction are not covered by this warranty. The factory or an authorized repair station must
perform warranty service. Service provided on equipment returned to the factory or authorized
repair station includes labor to replace defective parts. Goods returned must be shipped with
transportation and/or broker charges prepaid. SR Instruments, Inc.’s obligation is limited to
replacement of part, which has been so returned and is disclosed to SR Instruments, Inc.’s
satisfaction to be defective. The provision of this warranty clause is in lieu of all other warranties,
expressed or implied, and of all other obligations or liabilities in connection with the sale of said
articles. In no event shall SR Instruments, Inc. be liable for any subsequent or special damages.
Any misuse, improper installation, or tampering shall void this warranty.
DAMAGED SHIPMENTS
Title passes to purchaser upon delivery to Transportation Company. Purchaser should file any
claims for shortage or damage with the delivery carrier and should refuse any shipment that has
obvious external damage.
RETURN POLICY
All products being returned to SR Instruments, Inc. require a Return Goods Authorization number
(RGA). To receive an RGA, call our Customer Service at 716-693-5977 ext 103 or toll-free in the
USA and Canada at 800-654-6360 ext 103.
When inquiry is made, please supply model and serial numbers, purchase order and reason for
return.
Generally, deleted, damaged, and outdated merchandise will not be accepted for credit. A
minimum restocking charge of 15% will be assessed on return of current merchandise unless scale
is returned because of SR error.
No returns will be accepted after 30 days.
All returns are to be shipped FREIGHT PREPAID to: SR Instruments, Inc., 600 Young Street,
Tonawanda, NY 14150.
RESTOCKING FEE
15% fee will be assessed on return of current merchandise
No fees will be charged if the scale is returned because of an error on the part of SR
Instruments, Inc.
No returns accepted after 30 days.

Model SR241 Portable Infant/Adult Scale
Service Manual
Part No. MAN241_201006 Page 14 of 14
SInstruments, Inc., 600 Young Street, Tonawanda, NY 14150
Tel: [phone] Fax: [phone] URL: www.srscales.com
email: [email protected] Copyright 2020 SInstruments, Inc.
S
By SInstruments, Inc.
Precision & Technology in
Perfect Balance