Welch Allyn SureTemp 678 Technical Manual
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Welch Allyn SureTemp 678 Technical Manual

Welch Allyn SureTemp 678 Technical Manual

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Summary of Contents for Welch Allyn SureTemp 678

  • Page 1 Thermo Menu 678 Operation Manual 679 Operation Manual 679V Operation Manual ® SureTemp Model 678 & Model 679 Thermometer Technical Manual...
  • Page 2 © 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.

  • Page 3: Table Of Contents

    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................
  • Page 4 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..............

  • Page 5: List Of Figures

    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................

  • Page 6: Warranty

    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.

  • Page 7: Specifications

    ABS Plastic Case Material: 10.25 ounces with batteries and probe Weight (nominal): Welch Allyn Thermistor Probe. P/N 02678-000 Input: (ORAL 4’), P/N 02678-100 (ORAL 9’), 02679-000 (RECTAL 4’), AND 02679 -100 (RECTAL 9’) 28.9 o C to 42.2 o C (84.0 o F to 108.0 o F) Display range: ±...

  • Page 8: Terminology

    TERMINOLOGY Many standard abbreviations are used in this Technical Manual. Abbreviation Definition printed circuit board (the board itself) printed circuit assembly (the board with all its components) Liquid Crystal Display BATT Battery Digital Multi-Meter O-Scope Oscilloscope Component Reference Designators include: Abbreviation Definition capacitor...

  • Page 9: Operational Characteristics

    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.
  • Page 10 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.

  • Page 11: Self Tests

    Operational Characteristics Self Tests Instrument Reset/Self Tests If a problem is reported with an instrument, it is preferred that the user investigate operation before the unit is reset. However, resetting the electronics is the recommended starting point in the checkout process. The batteries must be removed from the instrument to reset the internal microprocessor electronics.

  • Page 12: Probe Warmer Circuit Self Tests

    Technical Manual Probe Warmer Circuit Self Tests Proper instrument functionality should be verified first as described in the Instrument Reset/Self Tests section (above) before a probe is installed. With a properly functioning instrument, the probe can be run through the self test. If the instrument is functioning properly and a probe is installed, the instrument will initiate the probe warmer self test during the instrument reset self test and whenever a probe is plugged in.

  • Page 13: Normal Mode

    Operational Characteristics Normal Mode After instrument and probe warmer self tests, the system is ready for use. Normal mode operation is the rapid mode of temperature taking. This is the default mode and is automatically selected when the probe is withdrawn from the probe well. 1.

  • Page 14: Monitor Mode

    Monitor mode is 5 minutes. Monitor mode is also useful in testing the accuracy of the combined probe/instrument system when the probe can be warmed to a known temperature, as with a Welch Allyn Model 9600 Calibration Tester or in a circulating water bath.

  • Page 15: F/C Conversion

    Operational Characteristics F/C Conversion When a final temperature is displayed (in Normal, Recall, or Monitor mode), pressing and releasing the Mode button will toggle the temperature between °F/°C. Note: A recalled temperature will be displayed in whichever scale (°F/°C) is selected at the time of recall.
  • Page 16 Observe the display, The display should show “r X.X” where “X.X” is a number such as 2.3. This can be helpful when discussing operation with Welch Allyn customer support. Press the Mode button for more than two seconds to advance to the Default Algorithm.
  • Page 17 Operational Characteristics 6. Instant Anti-Theft The user can select an anti-theft option that instructs the Audio Alarm System instrument to beep continuously (beginning after (Model 678 only) approximately 5 seconds) whenever the unit is removed from the wall holder. The user must defeat the Instant Anti-Theft Audio Alarm within 30 seconds after removal from the wall holder by holding the Mode button and removing the probe from the probe well, or by returning the unit to the wall holder.
  • Page 18 Technical Manual 1-10 Welch-Allyn, Inc.

  • Page 19: Preventive Maintenance

    2. PREVENTIVE MAINTENANCE The following preventive maintenance is recommended to maximize uninterrupted service with the M678 and M679 SureTemp Thermometers. Units which are in service on a regular basis should have the following preventive maintenance performed every 6 months: 1. Visually inspect the thermometer for physical damage which might cause future product failure.

  • Page 20: Battery Removal And Replacement

    9. Install the probe connector and insert the probe into the storage well to start the probe initialization process. 10. Verify proper calibration of the thermometer and probe using the Welch Allyn Model 9600 Calibration Tester. Battery Removal and Replacement 1.

  • Page 21: Calibration Testing

    9600. Refer to the Model 9600 Operation Manual for complete instructions. Note: All Welch Allyn and Diatek thermometers (thermistor and infrared ear thermometers) can be checked in the Model 9600. If you are having problems with the use of the Model 9600, refer to the Troubleshooting section in the Model 9600 Operation Manual .
  • Page 22 Technical Manual Welch-Allyn, Inc.

  • Page 23: Theory Of Operation

    4. THEORY OF OPERATION Technical Overview The heart of the Model 678 and Model 679 is comprised of two integrated circuits which provide most of the microcontroller and analog circuit functions. All control and display functions are governed by the microcontroller (U1). All probe analog data interfacing to the microcontroller is provided by U2.

  • Page 24: Probe Enhancements

    Technical Manual Probe Enhancements The Model 678 and Model 679 thermometers have the capability to detect probe type - oral / axillary vs. rectal. This allows the oral temperature-taking to be as fast as possible by using different operating modes based on probe type. Axillary temperatures are measured with oral probes in combination with the axillary mode, providing a temperature reading in about 15 seconds.

  • Page 25: Power Supply

    Theory of Operation The shape of the rising temperature curve is monitored and the best fit to a curve is found. When the curve fit is stable, the final predicted temperature is displayed. In the oral mode, if the prediction criteria is not met within 15 seconds of starting the prediction process, it will automatically switch to Monitor mode.

  • Page 26: Reset/Self Tests

    Technical Manual Reset/Self Tests Upon battery installation, (assuming that the electronics have been discharged sufficiently by pressing a user button with batteries removed) the microprocessor receives a power up reset signal from the components associated with the reset line at U1-12.

  • Page 27: Circuit Description

    Theory of Operation In effect, this is a single slope converter which measures the time constant of the measured resistance combined with a fixed capacitance. The time constant is measured by counting the time it takes for the voltage to decay from a fixed initial voltage level to a fixed lower voltage.

  • Page 28: Probe Identification Logic

    Technical Manual Q4 and Q5 and the base resistors R15 and R30 form the level shifter and drive circuit for the fixed end of the timing capacitor. R15 (4.7K) is selected to give adequate saturation on-resistance. R30 (10K) is selected so that a float on the input will not cause damage from cross-conduction if the input is left floating, yet supply enough current to the timing capacitor during recovery.

  • Page 29: Circuit Operation

    Theory of Operation Circuit Operation R10, R11 (both 1 M pullup resistors to reduce battery drain), J1-F(PROBE_1), J1- C(PROBE_0) and J1-E(GND) are used to provide logic 0 or 1 inputs to U1-17 and U1- 18 depending on whether a probe or cal key has been plugged into the Model 678 probe connector receptacle.

  • Page 30: Circuit Operation

    Technical Manual Circuit Operation The warmer circuitry consists of Q5, Q13, Q14, C1, C2, L1, D1, R1, R2, R3, R4, R5, R31, R32, and the heater resistor (27 ohms) connected across J1B and J1E. Line /HTRQ is pulled low by the uP which enables Q13 to turn on. /HTRC is then pulsed low which brings the base of Q5 low via capacitor C1.

  • Page 31: Probe Switch

    Theory of Operation Probe Switch When the probe has been inserted in the probe holder, the probe switch (S4) brings PROBE SW (U1-15) high (VCC). When the probe is removed from the probe holder, the probe switch brings PROBE SW (U1-15) low (GND). R6 (47K) allows the probe switch to be overridden by the test port.
  • Page 32 Technical Manual 4-10 Welch-Allyn, Inc.

  • Page 33: Troubleshooting

    5. TROUBLESHOOTING Many thermometer operational parameters can be tested for proper operation before the unit is taken apart and without needing any tools. Refer to Operational Characteristics on page 1-1 and in particular to the Setup and Biotech Mode sections for guidance on preliminary checks. If the trouble seems to be calibration related, refer to Calibration Testing on page 3-1.

  • Page 34: Equipment Required

    Technical Manual Instrument circuitry error codes are listed in the table below. CLASS ERR NUM SELF-TEST DESCRIPTION Probe E0.1 Probe heater accumulation test. Probe E0.2 Probe a/d pulse width test. Probe E0.3 Adaptive probe gain too high or too low test. Ambient E1.1 Ambient temperature high test.

  • Page 35: Troubleshooting Table

    Troubleshooting Troubleshooting Table SYMPTOM POSSIBLE CAUSE PROCEDURE No operation Dead batteries, no batteries, Refer to Battery Removal and battery missing, battery Replacement on page 2-2. Check incorrectly installed that all batteries are installed in proper direction. Reset electronics (see Instrument Reset/Self Tests on page 1-3).
  • Page 36 Technical Manual Troubleshooting Table (continued) SYMPTOM POSSIBLE CAUSE PROCEDURE Display problems Cracked LCD Inspect LCD for hairline cracks, especially (continued) in corners. Microprocessor failure Check for improper soldering of pins, crystal operation on O-scope, proper reset. No beeper sound Defective horn Replace horn.
  • Page 37 Troubleshooting Troubleshooting Table (continued) SYMPTOM POSSIBLE CAUSE PROCEDURE Probe: Wrong type Incorrect wiring of Oral probes should have a short between displayed (continued) probe pins B, E and F (refer to instrument PCB designators for probe pin definition). Rectal probes should have a short between pins E and F but open between pins B and E or F.
  • Page 38 Technical Manual Troubleshooting Table (continued) SYMPTOM POSSIBLE CAUSE PROCEDURE Battery Life Problems Excessive alarms The horn draws significant current. Excessive use in monitor During monitor mode the instrument is mode continously drawing current. Dead cell If cell voltage is down significantly in only one cell, this battery is defective.
  • Page 39 Troubleshooting Troubleshooting Table (continued) SYMPTOM POSSIBLE CAUSE PROCEDURE Monitor mode Probe malfunction Change probe or test calibration of temperature reading too entire system (instrument and probe) high with the M9600 Calibration Tester. Instrument malfunction Check calibration with Cal Key. Normal mode Probe malfunction Recharacterize probe (remove temperature reading too...

  • Page 40: Field Serviceable Repairs

    Some minor changes to the exact calibration point will be caused by changing R8, and R13, but as long as the proper type and tolerance resistors are used (0.1% and 0.05% as supplied by Welch Allyn), the unit will remain within specifications.

  • Page 41: Model 678/679 Replacement Parts

    Troubleshooting Model 678/679 Replacement Parts Part Number Description 25228-0000 (678 Only) SWITCH ARRAY, M678 25232-0000 HOUSING, FRONT, M678 (2 BTTNS) 25234-0000 HOUSING, REAR, M678/679 53009-000 BATTERY, ALKALINE 1.5V AA 70852-0000 LABEL, BLANK LASER 1.25 X 1.56 70866-0000 (678 Only) LABEL, FRONT, M678 70867-0000 (678 Only) LABEL, ICON, ID, M678 80128-1000...

  • Page 42: Replacement Parts-Circuit Board Assemblies

    Technical Manual Replacement Parts-Circuit Board Assemblies Part Description Reference Designator Number 21001-0011 PCA MAIN M678 W/BCKLGHT 46129-1050 CAP 1UF TANTCHIP 16V +/-20% 46138-0000 CAP, 10UF, 20%, 16V ALUM 46127-1030 CAP 0.01UF 100V X7R CHIP 0805- C19, C2, C20, C22, C5, C6 46136-0000 CAP, .33UF, 10%, 50V TANTB 46137-0000...
  • Page 43 Troubleshooting Part Number Description Reference Designator 21001-1010 PCA, MAIN, M678 F/C W/BCKLGHT 25229-0000 FRAME, LCD, M678/679 25230-0000 LIGHT PANEL (678 Only) 25231-0000 SPACER, EDAC, M678/679 58536-0000 CONNECTOR, ZEBRA .255X1.82x.10 70869-0000 LABEL, REFLECTIVE, M678 (678 Only) 60026-0000 LED, BACKLIGHT, YELLOW (678 Only) 58524-0000 CONNECTOR,6 COND,EDGE REC 60025-0000...

  • Page 44: Thermometer Disassembly

    Technical Manual Thermometer Disassembly Please note that if your thermometer is within the warranty period, you should return the unit to an authorized service representative for servicing; failure to do so will invalidate the warranty. WARNING: This instrument contains microelectronic devices which are highly susceptible to damage by static discharge.

  • Page 45: Figure 7 - Thermometer Assembly Drawing

    Troubleshooting Figure 7 - Thermometer Assembly Drawing Printed Circuit Assy. Battery 3 “AA” O rings (3) Battery Clips (2) Battery Clip Dual Label Front Push Button Switches Label Caution Serial Number Label Icons Front Housing Probe Well Battery Limiter Middle Housing Battery Wires Rear Housing Screws (4)

  • Page 46: Figure 8 - Main Pca

    Technical Manual Figure 8 - Main PCA Notes: Unless otherwise specified: 1. Maximum lead protrusion after trimming to be .060 inch. 2. Square pads indicate pin number 1 of components. 3. Silkscreened circles with no reference numbers are test points. 4.

  • Page 47: Figure 9 - Electronics Assembly

    Troubleshooting Notes: Unless otherwise specified: 1. Refer to manufacturing procedures 97033-0000, 97034-0000 and 97035-0000 for assembly instructions. Model 678 only. PC Assembly Zebra Connector LCD Frame Reflective Label Speaker Light Panel Yellow LED Reed Switch EDAC Spacer Probe Connector Probe Switch Figure 9 - Electronics Assembly ®...
  • Page 48 APPROVAL DATE THIS INFORMATION IS THE PROPERTY OF WELCH ALLYN CHECK WELCH ALLYN IT IS SUBMITTED IN CONFIDENCE PROPERTY OF WELCH ALLYN INC. AND IS NOT TO BE DISCLOSED PROJ. MGR. OR UTILIZED WITHOUT WRITTEN Q.A. PERMISSION PROBE CONNECTOR MFG. ENG.
  • Page 49 Technical Manual 5-16 Welch-Allyn, Inc. 70898-0000A...

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