Thermo Menu 678 Operation Manual 679 Operation Manual 679V Operation 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.
TABLE OF CONTENTS TABLE OF CONTENTS............................................................................................................. i LIST OF FIGURES ................................................................................................................... iii WARRANTY .............................................................................................................................iv SPECIFICATIONS .............................................................................
. THEORY OF OPERATION ................................................................................................ 4-1 Technical Overview ........................................................................................................... 4-1 Probe Enhancements................................................................................................. 4-2 Probe Switch .....................................................................................................................
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 ..............................................................................
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.
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: 28.9o C to 42.2o C (84.0o F to 108.0o F) • Laboratory Accuracy: ± 0.
TERMINOLOGY Many standard abbreviations are used in this Technical Manual.
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.
Technical Manual 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.
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. Follow the battery removal instructions in the Preventive Maintenance section.
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.
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. Upon withdrawal of the probe from its storage well, every segment on the display will be illuminated.
Technical Manual Monitor Mode The instrument can be placed in Monitor mode by pressing and holding the Mode switch for two seconds after a predictive (normal) temperature has been taken. This mode will be indicated on the display by a capital M in the bottom right corner. Monitor mode provides a direct readout of the probe temperature. This mode of operation has the ability to provide long term monitoring of a patient’s temperature.
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. This can also be changed during display. If pressing the Mode button does not change the scale of the displayed temperature, refer to Mode Button Problems in the Troubleshooting section.
Technical Manual If you cannot enter the Biotech mode, refer to Biotech Mode Problems in the Troubleshooting section. Function Settings 1. Software Version 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. 2.
Operational Characteristics 6. Instant Anti-Theft Audio Alarm System (Model 678 only) The user can select an anti-theft option that instructs the instrument to beep continuously (beginning after 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.
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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. 2. Clean the unit per instructions in the Directions for Use manual supplied with the thermometer and/or per the instructions below. 3.
Technical Manual This type of sterilization may cause some hazing of glossy plastic surfaces and should be used only when absolutely necessary. 1. Ensure that the probe is removed from its storage well and disconnected from the instrument. 2. Remove any probe covers from the probe and from the probe cover storage well. 3. Remove the batteries following the instructions in the Battery Removal and Replacement section below.
3. CALIBRATION TESTING The Calibration Key provides a convenient means of testing the thermometer. Calibration Key Procedure 1. Extract the probe and disconnect it from the thermometer. 2. Insert the Calibration Key (part number 01637-000) into the probe connector receptacle on the thermometer and observe the display. The display should read CAL for two seconds, and then go blank. 3. Insert a probe shaft into the probe storage well and remove it to initiate a temperature taking cycle.
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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. U2 functions as an A/D converter.
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. Rectal probes give a Normal mode temperature in about 15 seconds for both models.
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.
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. When power is applied continuously, C3 is charged slowly through R7, providing an active low reset to the microprocessor.
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. The ratio of this pulse width and the pulse width corresponding to a known calibration resistance (R13, 11.55K) is used to calculate the measured resistance.
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.
Theory of Operation Circuit Operation R10, R11 (both 1 MΩ pullup resistors to reduce battery drain), J1-F(PROBE_1), J1C(PROBE_0) and J1-E(GND) are used to provide logic 0 or 1 inputs to U1-17 and U118 depending on whether a probe or cal key has been plugged into the Model 678 probe connector receptacle.
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. Q5 turns on which in turn enables Q14 on. Base current from Q14 flows through R31 (1K) and R32 (1K).
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. Mode Button The mode button (S2) is a momentary contact switch. A pullup internal to the microprocessor normally pulls /MODE (U1-25) high, placing a logic “1” at this input.
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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.
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. Ambient E1.2 Ambient temperature low test. Battery E2.1 “Dead” battery test. Internal E3.1 RAM read/write test. Internal E3.2 ROM checksum test. Internal E3.3 CPU instruction test.
Troubleshooting Troubleshooting Table SYMPTOM POSSIBLE CAUSE No operation Dead batteries, no batteries, battery missing, battery incorrectly installed PROCEDURE Refer to Battery Removal and Replacement on page 2-2. Check that all batteries are installed in proper direction. Reset electronics (see Instrument Reset/Self Tests on page 1-3). If battery voltage is within specifications, refer to Biotech Mode on page 1-7 and enter Biotech mode to measure battery voltage as seen by electronics.
Technical Manual Troubleshooting Table (continued) SYMPTOM Display problems (continued) No beeper sound No Timer function No Backlight 5-4 POSSIBLE CAUSE PROCEDURE Cracked LCD Inspect LCD for hairline cracks, especially in corners. Microprocessor failure Check for improper soldering of pins, crystal operation on O-scope, proper reset. Defective horn Replace horn. Broken connection Check continuity from U1-49 to horn pin 2 and from ground to horn pin 1.
Troubleshooting Troubleshooting Table (continued) SYMPTOM POSSIBLE CAUSE Probe: Wrong type displayed (continued) Incorrect wiring of probe PROCEDURE Oral probes should have a short between 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. Replace with new probe. Normal/Monitor Mode switching problems Ambient above 33.9°C (93.0°F) Causes auto switch to Monitor mode.
Technical Manual Troubleshooting Table (continued) SYMPTOM Battery Life Problems 5-6 POSSIBLE CAUSE PROCEDURE Excessive alarms Excessive use in monitor mode The horn draws significant current. During monitor mode the instrument is continously drawing current. Dead cell If cell voltage is down significantly in only one cell, this battery is defective. All batteries should drain at the same rate.
Troubleshooting Troubleshooting Table (continued) SYMPTOM POSSIBLE CAUSE Monitor mode temperature reading too high Normal mode temperature reading too low PROCEDURE Probe malfunction Change probe or test calibration of entire system (instrument and probe) with the M9600 Calibration Tester. Instrument malfunction Check calibration with Cal Key. Probe malfunction Recharacterize probe (remove completely from instrument and reinstall). Or, change probe.
Technical Manual Field Serviceable Repairs Repairs are considered field serviceable if the repair will not alter the calibration or proper operation of the instrument. • All probes designed to work with the thermometer are fully interchangeable. • All components in the Model 678 and Model 679 can be replaced without affecting instrument operation or calibration.
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 TUBING,SILICONE,125 X .25 X.3 83174-0000 SCREW,PLASTITE,2-28 X 1/2 P-PL 85259-0000 O-RING, 208 I.D.
Technical Manual Replacement Parts-Circuit Board Assemblies 5-10 Part Number Description Reference Designator 21001-0011 PCA MAIN M678 W/BCKLGHT 46129-1050 CAP 1UF TANTCHIP 16V +/-20% C1 46138-0000 CAP, 10UF, 20%, 16V ALUM C17 46127-1030 CAP 0.01UF 100V X7R CHIP 0805- C19, C2, C20, C22, C5, C6 46136-0000 CAP, .33UF, 10%, 50V TANTB C21 46137-0000 CAP, CHIP, 1UF, 20%, 50V ALUM C25 46140-0000 CAP, CHIP, 22PF, 5%, 50V 0805 C26, C27 46022-000 CAP 0.
Troubleshooting ® Part Number Description 21001-1010 PCA, MAIN, M678 F/C W/BCKLGHT 25229-0000 FRAME, LCD, M678/679 25230-0000 (678 Only) LIGHT PANEL 25231-0000 SPACER, EDAC, M678/679 58536-0000 CONNECTOR, ZEBRA .255X1.82x.
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. Use proper handling and grounding techniques while working on the internal electronics. 1. Withdraw the probe from the probe storage well. 2.
Troubleshooting Figure 7 - Thermometer Assembly Drawing ® 1 Printed Circuit Assy. 7 Battery 3 “AA” 13 O rings (3) 2 Battery Clips (2) 8 Battery Clip Dual 14 Label Front 3 Push Button Switches 9 Label Caution Serial Number 15 Label Icons 4 Front Housing 10 Probe Well 16 Battery Limiter 5 Middle Housing 11 Battery Wires 6.
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. All post-mounting transportation and storage is to be within anti-static packing and under anti-electrostatic discharge handling packaging practices. 5-14 Welch-Allyn, Inc.
Troubleshooting Notes: Unless otherwise specified: 1. Refer to manufacturing procedures 97033-0000, 97034-0000 and 97035-0000 for assembly instructions. Model 678 only.
1 2 3 4 5 6 7 8 REVISIONS REV VCC DESCRIPTION ECO A INITIAL RELEASE 2835 11/7/96 B REPLACED x1 RESONATOR WITH CRYSTAL ADDED CAPACITORS C26 AND C27 REMOVED P11.4 FROM GROUND CONNECTED P11.4 TO P11.5 DATE 2835-10 1/30/97 C MOVED ONE SIDE OF R1 FROM Q5 EMITTER TO VCC CHANGED VALUE OF R1 FROM 470K TO 3M 3192 6/10/98 CON12 J4 1 2 3 4 5 6 7 8 9 10 11 12 VCC E2 1 3 AA 1 1 J6 /HOST_WAKEUP ALKALINE + 2 1 VCC 3.0-5.
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