OPERATING MANUAL
THERMALERT MONITORING THERMOMETER
TH-5
CONTENTS
Section
1.0 INTRODUCTION
2.0 INITIAL INSTALLATION
3.0 PRECAUTIONS
4.0 DIRECTIONS FOR USE
5.0 REPLACING BATTERIES
6.0 CHECKING CALIBRATION
7.0 USE OF THERMALERT
WITH CHART RECORDER
8.0 SPECIFICATIONS
9.0 TEMPERATURE MEASUREMENT WITH
THERMOCOUPLES
10.0 REPAIRS AND RECALIBRATION
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OPERATING INSTRUCTIONS
THERMALERT MONITORING THERMOMETER, TH-5
1.0 The Physitemp Clinical Monitoring Instruments, Thermalerts TH-5 and TH-8, are compact,
portable, battery operated digital readout thermometers for continuous clinical temperature
monitoring.
2.0 INITIAL INSTALLATION
2.1 Plug any Physitemp type T thermocouple probe into the blue polarized socket on the rear
of the instrument.
2.2 The TH-5 thermometer is designed
to mount as follows:
(a) Flat, on rubber feet provided.
(b) Bench mounting with optional
tilt stand (TTS-4).
3.0 PRECAUTIONS
3.1 As with any temperature monitoring system, use suitable accepted technique during eletro-
surgical procedures to minimize the possibility that the probe cable will serve as an alternate
path for radio frequency current and burn the patient.
- Properly locate an adequate electrosurgical dispersive electrode close to the active
surgical site.
- Do not drape the probe cable over grounded metallic surfaces or intertwine it with the
cables of the electrosurgical generator.
3.2 Never pull directly on the probe cable to disconnect.
3.3 Gas sterilization or autoclaving of the instrument is not recommended.
3.4 Do not immerse the instrument in liquids for cleaning. If necessary, clean the instrument
case with a cloth moistened with a mild non-staining germicidal detergent and warm water.
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4.0 DIRECTIONS FOR USE
4.1 Connect any Physitemp type T thermocouple probe to the blue polarized socket on the rear
of the instrument.
4.2 Switch ON by depressing switch on front of unit - switch shows orange when in ON position.
For several seconds the digital display should read “1888” as a segment check. Do not use if any display segment is inoperative. A calibration check is not necessary before each use.
4.3 Read temperature. Leave on for monitoring as long as desired.
4.4 Switch off after use.
4.5 Special Display Indications
1 A single digit 1 to the left signifies reading is outside
instrument range.
0 A single digit 0 to the left indicates an open cable or
probe. Check connection. If this is good, replace probe.
A flashing colon in the center of the display signifies
low battery alert. Accurate readings will still be
obtained, and it is not necessary to discontinue use
immediately. Install new batteries the next time the
unit is turned off.
A non-flashing colon signifies imminent battery
failure. Install new batteries to ensure accurate
readings.
5.0 REPLACING BATTERIES
5.1 CAUTION: Use only alkaline “C" cell batteries. Switch instrument OFF.
5.2 Grasp "squeeze release" on back panel and pull off battery retainer.
5.3 Remove battery connectors and slide out battery holder.
5.4 Discard old batteries and replace with fresh “C" cells.
5.5 Replace battery holder and refit connectors.
5.6 Insert top edge of battery retainer into lip of case. While grasping "squeeze release" push
retainer in until flush with back of case.
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6.0 CHECKING CALIBRATION
6.1 The Thermalert TH-5 thermometer incorporates an automatic zeroing amplifier which produces
near-perfect stability of calibration. A calibration check is not necessary before each use. Under normal circumstances, the instrument will provide years of service without requiring recalibration.
6.2 Should it be suspected that the instrument is out of calibration, it may be checked with the
Physitemp type T calibrator (Model CT-3), or if this is unavailable, with an NIST calibrated thermometer. Verifying instrument calibration with an NIST calibrated thermometer requires extremely careful
technique, an accurate reference standard thermometer, and a reasonably draft-free location. The following apparatus and supplies are needed:
1 - quart thermos flask with 2-hole cork
Stirrer
NIST traceable mercury in glass thermometer, 0.05°
graduations, partial immersion, 25-50°C (78-122°F)
with ice point scale.
Physitemp type T temperature probe
Ice made from distilled water
Distilled water
6.3 Preparation:
a) Crush the ice and place it in the thermos flask, at least 3/4 full. Add distilled water. Leave for
30 minutes to allow temperature to stabilize, stirring periodically.
b) Immerse the standard mercury-in-glass thermometer in the ice bath to the immersion
mark on the stem. Stir the bath well and compare with thermometer reading at 0°C with the
correction table supplied with the thermometer. If the error is greater than 0.0°C, wait 10
minutes, stir the water bath and remeasure. If the error remains greater, test with another
standard thermometer.
6.4 A complete calibration check requires two different measurements, one for each of the
temperature ranges of the TH-5.
6.5 Checking low end of temperature range:
Fill a thermos flask with a mixture of hot and cold water to produce a temperature of
approximately 25°C. Attach any Physitemp type T thermocouple probe to the standard
mercury thermometer so that the sensor is at the same level as the mercury bulb, and
immerse in the flask to the immersion depth marked on the stem. Do not allow probe or
thermometer to touch the sides of the flask. Connect the probe to the TH-5 and switch it
ON. Stir the bath well and wait 5 - 10 minutes. Ensure the flashing colon (battery warning)
is not visible before reading the instrument and then the mercury thermometer to .05°C.
Make a note of both readings.
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6.6 Checking high end of temperature range:
Prepare a water bath at approximately 45°C. Follow measurement instructions given in
Section 6.5.
6.7 Allowing for some reading error in the mercury thermometer (there can be none in reading the
digital instrument display) and possible probe error, readings should agree within the limits noted in
Section 9.7) This means, as an approximate rule-of-thumb, that differences between standard and
instrument readings should not exceed 0.2°C. The exact error limits depend on the actual temperature at
which the calibration is checked.
6.8 If the instrument appears to be out of calibration based on the foregoing checks, it should be
returned for service (see Section 10).
.
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7.0 USE OF THERMALERT WITH A CHART RECORDER
7.1 Analog output is optional on Model TH-5.
WARNING: Use of AC-powered equipment with Physitemp Thermometers. As it is powered
entirely by low-voltage batteries, Physitemp Thermometer TH-5 presents no safety hazard to
patients. However, caution is advised when using the TH-5 with a chart recorder for recording
patient temperature. Such auxiliary equipment, when AC-powered and in faulty condition, can
create a potential shock hazard.
Hazard to a Grounded Patient
The circuit of the TH-5 is such that a low-impedance path exists from the analog output socket
to the probe input socket. The TH-5 with sensor probe could therefore act as an electrical conductor between a faulty AC-powered recorder and the patient. Leakage current could exceed
safe limits.
Hazard to an Ungrounded Patient
Some chart recorders have a permanently grounded input binding post. If a patient is connected
to faulty AC-powered equipment and becomes live, a leakage path to ground would exist
between the sensor probe and the recorder. Current safety limits could be exceeded.
If recording is essential: Use a recorder which meets AAMI safe current limit standards.
Before connecting thermometer to recorder, consult a competent
engineer about shock hazard. Remove connector plug from thermometer analog output when not in use.
7.2 A DC output with amplitude approximately proportional to instrument reading is provided from a stereo-type jack on the back panel. A mating plug is supplied for connection to the
recorder. This plug may be left in the socket until it is required for use. The output of the TH-5
is 2 kilohms impedance, so connection to a potentiometric recorder will not affect either the
calibration or accuracy.
Connection diagram for the plug:
7.3 Recorder sensitivity and pen zero must be adjusted so that the lines on the chart correspond to the desired range of temperatures
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NEGATIVE (RETURN)
POSITIVE (SIGNAL, OUTPUT)
8.0 SPECIFICATIONS
Temperature Range 25°C - 45°C
Resolution 0.1°C
Repeatability 0.1°C
Calibration Conforms to National
Institute of Standards and Technology tables
(Monograph 125).
Instrument Accuracy 0.1°C digit
Sensors Any Physitemp type T thermocouple probe.
Ambient Operating Range 15°C - 45°C
Readout 3 1/2 digits, LCD 0.5” high
Display check Automatic “1888” displayed after switch-on
tests all segments.
Batteries 4 “C” cells. Alkaline or Mercury may be used.
Carbon-Zinc cells are not recommended.
Battery Life Expectancy 1200 hours continuous (alkaline)
Analog Output Optional extra, approx. 25mV/°C
Size 3” H x 6”1 W x 6 1/4” D
Weight 2 1/2 lbs.
Leakage Current Instrument is isolated from ground and from mounting
supports to 5000 volts DC. Low capacitance design
minimizes risk caused by faulty patient grounding
during electrosurgery. Leakage is less than lOμA at 6OHz.
Safety Features Conforms to NFPA 99 Inhalation Anesthetics 1984 (operating
voltage less than lOV), battery operated, suitable for use with
flammable anesthetics. ANSI/AAMI Safe Current Limits
for Electronic Apparatus,1978
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9.0 TEMPERATURE MEASUREMENT WITH THERMOCOUPLE SENSORS
9.1 The thermocouple is a simple and widely accepted device for measuring temperature. It
comprises two wires of dissimilar metals fused together to form a junction which produces an
electrical output proportional to temperature. The National Institute of Standards and
Technology (NIST Monograph 125, 1974) has tabulated the voltage/temperature relationships
of many commonly used thermocouple pairs; their tables on copper/constantan form the basis
for calibration of Physitemp thermometers.
9.2 At one time, accurate thermocouple temperature measurements needed elaborate potentiometers and reference to a source of known temperature, such as an ice bath. The advent of
modern solid state devices has made possible the design of an inexpensive thermocouple thermometer which is direct reading. The first of these was Bailey thermometer BAT-4, which was
designed in 1969 and is now in use throughout the world. Your Thermalert is an advanced version of the original equipment using the latest low power digital technology and compensated
electronic reference circuitry.
9.3 As compared with thermistor sensors which were formerly used exclusively in portable
thermometers, thermocouples have these advantages:
(a) wide temperature range, e.g. -200°C to over +1300°C.
(b) High stability of output.
(c) Interchangeability - no recalibration required.
(d) Accuracy traceable to NIST calibrations.
(e) Low cost; users can even make their own sensors.
(f) Microscopic size when needed, as in Physitemp microprobes.
(g) Nearly instant response.
(h) Better measurement accuracy due to low mass with smaller heat loss.
9.4 The main disadvantage of the thermocouple low sensitivity was overcome by the development of auto zeroing amplifiers which are now used in all Physitemp thermometers. This
typeof amplifier is essentially drift-free. It makes possible an electronic thermometer which is
permanently calibrated, just like a mercury thermometer. The following notes may help the user
to avoid some of the errors most frequently made in temperature measurement.
9.5 Faulty measurement technique with any type of thermometer can produce errors of several degrees. Errors attributed to "out of calibration" equipment can often be corrected by a simple change of technique.
9.6 Thermocouple probes, like all other temperature sensing devices, must be placed so that
they reach, as closely as possible, the temperature of the material to be measured. Probes are
tip-sensitive, but when measuring the temperatures of liquids, semi-solids or hard surfaces, it is
not sufficient to bring only the tip into contact with the material being measured. his is because
there will be loss of heat along both the thermocouple wires and their sheath, so readings will
be low. The effect can be greatly reduced if part of the metal sheath is also placed in contact
with the material. In liquids and semi-solids, the tip and sheath are simply immersed; on solid
surfaces, the sheath is laid against the surface.
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Here is a useful rough rule: Heat leakage effects are substantially reduced when an
amount of probe equal to 10 or more sheath diameters is immersed or laid on the suface.
For example, with a probe of 1/16” diameter, 10 x 1/16” = 10/16 = .625 = the minimum
immersion depth.
9.7 Errors between thermocouple probes. All Physitemp probes and sensors are made with
thermocouple wire that has been specially tested to meet our own stringent standards. Our
probes are guaranteed accurate to within 0.1°C in the range 0-50°C. Copper-Constantan (type
T) thermocouples from other manufacturers are normally close to this accuracy provided they
are ordered to "special limits of error," and so are suitable for use with our thermometer. This
interchangeability of sensor, including microprobes, is a major advantage of Physitemp thermocouple thermometers.
9.8 Measurements in Liquids. These are quite easy to make, because
there is good thermal contact between liquid and probe. The latter quickly
reaches liquid temperature and readings can be taken within a few seconds.
However, a liquid which has been heated above or cooled below ambient
will be losing or gaining heat, and convection currents will give rise to
temperature variations of up to several degrees. These variations can be
reduced by vigorous stirring. This simple precaution must always be taken.
9.9 Measurements of Air Temperature. Temperature can vary widely in different parts of a
room; differences of at least several degrees will usually be noted. When a microprobe is used
to indicate air temperature, readings will often fluctuate rapidly, responding to actual temperature changes caused by air currents. Breathing near the microprobe will produce wide fluctuations. These effects indicate the sensitivity of the Thermalert/microprobe combination, due to
high discrimination of the instrument and almost instant response of the probe. Fluctuations can
easily be eliminated by bringing the probe into contact with a metallic object, thus increasing its
effective mass and slowing the response. Using a larger probe will have the same results.
9.10 Measurements on Solid Surfaces. These are most easily made with surface probes such
as our BT-1 and MT-D. The right-angled tip provides the 10 diameters of probe contact speci-
fied in Section 9.6. Straight probes may also be used,
provided that sufficient shaft length is in contact with
the surface to be measured. In general, the smaller the
probe, the more accurately it will measure the surface
temperature of a solid. For instance, an MT-29 microprobe, because of its small size, needs to be in contact
with the surface for as little as 1/8”. SST-1 has a 1/4”
gold disc sensor. Gold is an excellent conductor, and
is non-allergenic and non-polluting. It makes a fine
skin surface probe.
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SST-1
10.0 REPAIRS AND RECALIBRATION
10.1 In the event that a Thermalert Monitoring Thermometer is to be returned for repair and
recalibration, please pack it with care and send it prepaid to:
Physitemp Instruments, Inc.
Service Department
154 Huron Avenue
Clifton, NJ 07013 USA
Please include with the instrument:
(1) A note describing any problems encountered.
(2) The name and telephone number of the user or other person we can contact.
(3) The complete return address for shipping.
10.2 A Service Manual for the TH-5 is available at additional charge. It includes schematic,
component locator, trouble-shooting guide and complete calibration instructions. Specified test
equipment is required for recalibration or other servicing. Consult Physitemp Inc. for further
service information by telephone at:
Tel: 973-779-5577
Fax: 973-779-5954
E-mail: physitemp@aol.com
10.3 Physitemp Instruments Inc. warrants this instrument to be free from defects in material
and workmanship for 12 months from date of shipment. Repair or replacement will be made at
no charge at the discretion of Physitemp if the defect is not the result of misuse or abuse.
Physitemp accepts no consequential liabilty for delay in delivery, alleged faulty performance of
the product, or for any other cause.
Cables and probes are considered expendable and are not covered by this warranty. See separate warranty enclosed with probe.
For your protection, please pack returned items carefully, and insure them against possible damage or loss in transit. Physitemp will not be responsible for damage resulting from careless or
inadequate packaging. Pleasereturn freight prepaid.
During the warranty period, the instrument may also be returned for a free calibration check.
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