Welch Allyn SureTemp 678 User manual

SureTemp®
Model 678 & Model 679 Thermometer
Technical Manual

© 1997 by Welch Allyn, Inc. All rights reserved. No part of this manual may be
reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopy, without prior consent in writing from Welch
Allyn. Printed in the U.S.A.
Welch Allyn and SureTemp are trademarks of Welch Allyn, Inc. All rights
reserved.

SureTemp
®
Model 678/SureTemp
®
Model 679 i
TABLE OF CONTENTS
TABLE OF CONTENTS............................................................................................................. i
LIST OF FIGURES...................................................................................................................iii
WARRANTY.............................................................................................................................iv
SPECIFICATIONS.....................................................................................................................v
TERMINOLOGY.......................................................................................................................vi
1. OPERATIONAL CHARACTERISTICS...............................................................................1-1
Basic System Description..................................................................................................1-1
Self Tests..........................................................................................................................1-3
Instrument Reset/Self Tests.......................................................................................1-3
Display Test ...............................................................................................................1-3
Probe Warmer Circuit Self Tests................................................................................1-4
Battery Life........................................................................................................................1-4
Normal Mode.....................................................................................................................1-5
Monitor Mode ....................................................................................................................1-6
Pulse Timer Mode (Model 678 only)..................................................................................1-6
Backlight (Model 678 only).........................................................................................1-6
F/C Conversion ..........................................................................................................1-7
Temperature Recall....................................................................................................1-7
Biotech Mode ....................................................................................................................1-7
2. PREVENTIVE MAINTENANCE .........................................................................................2-1
Cleaning and Sterilization..................................................................................................2-1
Routine Cleaning........................................................................................................2-1
ETO Gas Sterilization Procedure................................................................................2-1
Battery Removal and Replacement...................................................................................2-2
3. CALIBRATION TESTING..................................................................................................3-1
Calibration Key Procedure.................................................................................................3-1
Model 9600 Calibration Testing Procedure........................................................................3-1

ii Welch-Allyn, Inc.
4. THEORY OF OPERATION................................................................................................4-1
Technical Overview...........................................................................................................4-1
Probe Enhancements.................................................................................................4-2
Probe Switch.....................................................................................................................4-2
Normal Mode.....................................................................................................................4-2
Power Supply....................................................................................................................4-3
Low Battery Detection ................................................................................................4-3
Microcontroller............................................................................................................4-3
Reset/Self Tests.........................................................................................................4-4
Microprocessor Clock.................................................................................................4-4
Temperature Measurement and Display.....................................................................4-4
Temperature Measurement A/D Converter.................................................................4-4
Theory of Operation ...................................................................................................4-4
Circuit Description......................................................................................................4-5
Probe Identification Logic..................................................................................................4-6
Basic Function............................................................................................................4-6
Circuit Operation ........................................................................................................4-7
Probe Warming ( Oral probes only)...................................................................................4-7
Theory of Operation ...................................................................................................4-7
Circuit Operation ........................................................................................................4-8
Other Components............................................................................................................4-8
Liquid Crystal Display.................................................................................................4-8
LCD Backlight (Model 678 Only) ................................................................................4-8
Probe Switch..............................................................................................................4-9
Mode Button...............................................................................................................4-9
Timer Button (678 Only).............................................................................................4-9
Serial Communications Port.......................................................................................4-9
Horn...........................................................................................................................4-9
5. TROUBLESHOOTING.......................................................................................................5-1
Error Codes.......................................................................................................................5-1
Equipment Required..........................................................................................................5-2
Troubleshooting Table.......................................................................................................5-3
Field Serviceable Repairs..................................................................................................5-8
Field Serviceable Parts......................................................................................................5-8
Model 678/679 Replacement Parts....................................................................................5-9
Replacement Parts-Circuit Board Assemblies.................................................................5-10
Thermometer Disassembly..............................................................................................5-12

SureTemp
®
Model 678/SureTemp
®
Model 679 iii
LIST OF FIGURES
FIGURE 1 - THERMOMETER DIAGRAM..............................................................................1-1
FIGURE 2 - M678 DISPLAY..................................................................................................1-3
FIGURE 3 - SYSTEM BLOCK DIAGRAM..............................................................................4-1
FIGURE 4 - PROBE LOGIC CIRCUITRY..............................................................................4-6
FIGURE 5 - PROBE LOGIC DIAGRAM.................................................................................4-6
FIGURE 6 - SELF-TEST /ERROR TABLE.............................................................................5-2
FIGURE 7 - THERMOMETER ASSEMBLY DRAWING.......................................................5-13
FIGURE 8 - MAIN PCA........................................................................................................5-14
FIGURE 9 - ELECTRONICS ASSEMBLY............................................................................5-15
FIGURE 10 - SCHEMATICS................................................................................................5-17

iv Welch-Allyn, Inc.
WARRANTY
3-YEAR LIMITED WARRANTY ON NEW M678 AND ON M679 ONE PER ROOM
INSTRUMENTS. 1-YEAR LIMITED WARRANTY ON NEW M679 INSTRUMENT:
Instrumentation purchased new from Welch Allyn, Inc. (Welch Allyn) is warranted to
be free from original defects in material and workmanship under normal use and
service for a period of three years for the M678 and one per room M679 and one
year for the M679 from the date of first shipment from Welch Allyn. This warranty
shall be fulfilled by Welch Allyn or its authorized representative repairing or replacing
at Welch Allyn's discretion, any such defect, free of charge for parts and labor.
Welch Allyn should be notified via telephone of any defective product and the item
should be immediately returned, securely packaged and postage prepaid to Welch
Allyn. Loss or damage in shipment shall be at purchaser's risk.
Welch Allyn will not be responsible for loss associated with the use of any Welch Allyn
product that (1) has had the serial number defaced, (2) has been repaired by anyone
other than an authorized Welch Allyn Service Representative, (3) has been altered, or
(4) has been used in a manner other than in accordance with instructions.
THIS WARRANTY IS EXCLUSIVE AND IN LIEU OF ANY IMPLIED WARRANTY OR
MERCHANTABILITY, FITNESS FOR PARTICULAR PURPOSE, OR OTHER
WARRANTY OF QUALITY, WHETHER EXPRESSED OR IMPLIED. WELCH ALLYN
WILL NOT BE LIABLE FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES.
The information in this manual has been carefully reviewed and is believed to be
accurate; however, no responsibility is assumed for inaccuracies. Furthermore, this
information does not convey to the purchaser of Welch Allyn or Diatek devices any
license under the patent rights to the manufacturer.

SureTemp
®
Model 678/SureTemp
®
Model 679 v
SPECIFICATIONS
• Case Dimensions
(nominal): 2.25 in. x 3 in. x 7 in
5.7 cm x 7.6 cm. x 17.8 cm
• Case Material: ABS Plastic
• Weight (nominal): 10.25 ounces with batteries and probe
• Input: Welch Allyn Thermistor Probe. P/N 02678-000
(ORAL 4’), P/N 02678-100 (ORAL 9’), 02679-000
(RECTAL 4’), AND 02679 -100 (RECTAL 9’)
• Display range: 28.9oC to 42.2oC (84.0o F to 108.0o F)
• Laboratory Accuracy: ± 0.2o F in the Monitor mode and in a water bath
per Welch Allyn document number 90565-000
• Clinical Accuracy: Meets the ASTM E1112-86 clinical test standard
• Push buttons: Mode and Pulse Timer
• Mode Button: Selects oF/ oC, Oral, Axillary and Monitor Modes
• Probes: Interchangeable Oral (also used for Axillary) and
Rectal
• Power Source: Three “AA” Batteries
• Battery Operating Life: Approximately 5,000 temperature measurements
(At 72oF ambient temperature)
• Display Type: Liquid Crystal Display, 3½ digits plus special icons
• Operating temperature: 16oC to 40o C (60.8 o F-104o F) @ 15% to 95%
RH non-condensing per ASTM E1112-86
• Storage Temperature: -20oC to 50oC (-4oF-120o F) @ 15% to 95%
RH non-condensing per ASTM E1112-86

vi Welch-Allyn, Inc.
TERMINOLOGY
Many standard abbreviations are used in this Technical Manual.
Abbreviation Definition
PCB printed circuit board
(the board itself)
PCA printed circuit assembly
(the board with all its components)
LCD Liquid Crystal Display
BATT Battery
DMM Digital Multi-Meter
O-Scope Oscilloscope
Component Reference Designators include:
Abbreviation Definition
C capacitor
D diode
E test point
J connector jack
L inductor
P connector plug
Q transistor
R resistor
S switch
T transformer
U integrated circuit
X crystal, resonator

SureTemp
®
Model 678/SureTemp
®
Model 679 1-1
1. OPERATIONAL CHARACTERISTICS
Note: This manual describes both the Model 678 and the Model 679 thermometers.
The bulk of the discussion is equally applicable to both products. Where there
are differences, it will be noted as to which instrument the discussion applies.
The Welch Allyn Model 678 and 679 Thermometers are the next generation of
thermistor based medical grade thermometers providing the accuracy and ease of use
of thermistor technology as in the well known Model 675. The Model 678 and Model
679 provide a Normal mode oral temperature in about 4 seconds, significantly faster
than the typical 30-40 second average time to temperature in earlier products.
Basic end user operation of the Model 678 and Model 679 is covered in the
User’s
Manual
and this manual assumes an understanding of these operations. This chapter
will help you determine if the Model 678/679 is functioning properly and, if it is not,
refer you to the proper section to isolate the problem.
Note: There are many things that can be done to check operation before the unit is
disassembled. This section will cover these normal operating actions.
Basic System Description
The thermometer system consists of five main components: The batteries, the
thermometer instrument, the wall mount, the probe and the probe cover.
1. Probe cover box 6. Probe Handle
2. Display 7. Probe storage well
3. Timer button (678 only) 8. Probe connector receptacle
4. Mode button 9. Probe cover storage well/ Battery cover
5. Probe cover ejection button
Figure 1 - Thermometer Diagram

Technical Manual
1-2 Welch-Allyn, Inc.
Batteries The Model 678 and Model 679 thermometers use three standard
alkaline “AA” cells. These batteries are readily available and
provide long life for reduced down time. No battery charging is
required.
Note: The use of Ni-Cad rechargeable batteries is allowed. The
nominal cell voltage of 1.2 volts for Ni-Cad (vs. 1.5 volts for
alkaline) combined with the lower actual capacity than
alkaline will result in a much shorter time between battery
charges than alkaline battery life.
Instrument The main instrument operates very similarly to the Model 675.
Basic operation has been kept similar to that of the Model 675 to
ease learning and use.
Wall Mount The wall holder is easily secured to a wall (or rolling stand). An
optional locking mechanism with a removable key for securing the
instrument is available. Through the use of available long probe
cords, the thermometer can be used without removing it from the
wall holder.
Probe The probe is similar to earlier probes. Model 670/675 probes
are incompatible with Model 678/Model 679 instruments, but
Model 767 and Welch Allyn Vital Signs Monitor probes can be
used in Model 678/Model 679 thermometers.
Probe Covers The probe covers are unchanged from previous models and are
compatible across all Welch Allyn and Diatek thermistor based
thermometers.
Welch Allyn’s thermistor-based probes can be identified by color
combinations as indicated in the following table.
Handle
Color Top Color Cord Color Connector Color Model # Probe Type
Green Green Green or Black Green M600 Oral
Red Red Green or Black Green M600 Rectal
Green Green Green Modular Phone style M650 Oral
Red Red Green Modular Phone style M650 Rectal
White Blue White Blue M670/M675 Oral
White Red White Red M670/M675 Rectal
White Blue White White with latch M678/679/767 Oral
White Red White White with latch M678/679/767 Rectal