Digital Thermometers
Instruction Manual
Models 868 and 869
Publication Date: January 2005
Document Number: 869-901-01CD Rev. E
This owner’s manual was as current as possible when this product was manufactured. However, products are constantly being updated and improved. Because of
this, some differences may occur between the description in this manual and the
product you received.
TABLE OF CONTENTS
Specifications.......................................................................................1
General Information.............................................................................3
Manual Addenda..................................................................................3
Optional Accessories............................................................................3
Preparation for Use..............................................................................4
Battery Installation/Replacement..........................................................5
Operation..............................................................................................6
Safety Symbols and Terms...................................................................9
Verification Procedure.........................................................................10
Calibration...........................................................................................12
Warranty Information ..........................................................................15
Limitation of Warrantly.........................................................................15
Statement of Calibration......................................................................15
Copyright 2003 TEGAM, Inc. All rights reserved.
SPECIFICATIONS
MODEL 868 SPECIFICATIONS
TEMPERATURE SENSOR TYPE: 3 wire or 4 wire 100 Ohm Platinum RTD
(alpha = 0.00385).
4 WIRE
TEMPERATURE ACCURACY*
RANGE SPAN RESOLUTION (65° to 82°F; 1 Year)
200°F -100.0° to 199.9° 0.1° ±0.4°F
-199.9° to -100.1° 0.1° ±1.0°F
1100°F -100° to 1100° 1° ±2°F
-360° to -101° 1° ±4°F
*ACCURACY: Includes DIN 43 760 (ITS-90) conformity, repeatabilitiy, temperature
coefficient (65° to 82°F), time stability (1 year) and errors with up to 50 ohms
of lead resistance (each lead). Excludes probe errors; however probe errors
around 32°F may be compensated by an internal adjustment.
REPEATABILITY: 0.2°F typical for 1 week at constant ambient temperature.
TEMPERATURE COEFFICIENT: 65° to 82°F; included in accuracy specification.
From 14° to 65° and 82° to 122°F: less than ±0.015°F/°F.
MAXIMUM LEAD RESISTANCE (each lead): 4 Wire; 50 ohms
3 Wire; 10 ohms
SENSOR CURRENT:500µA maximum.
MODEL 869 SPECIFICATIONS
TEMPERATURE SENSOR TYPE: 3 wire or 4 wire 100 Ohm Platinum RTD
(alpha = 0.00385).
4 WIRE
TEMPERATURE ACCURACY*
RANGE SPAN RESOLUTION (18°to 28°C;1 Year)
200°C -100.0° to 199.9° 0.1° ±0.3°C
-199.9° to -100.1° 0.1° ±1.5°C
630°C -100° to 630° 1° ±1°C
-220° to -101° 1° ±2°C
*ACCURACY: Includes DIN 43 760 (ITS-90) conformity, repeatabilitiy, temperature
coefficient (18° to 28°C), time stability (1 year) and errors with up to 50 ohms
of lead resistance (each lead). Excludes probe errors; however probe errors
around 0°C may be compensated by an internal adjustment.
REPEATABILITY: 0.1°C typical for 1 week at constant ambient temperature.
TEMPERATURE COEFFICIENT: 18° to 28°C; included in accuracy specification.
From -10° to 18° and 28° to 50°C: less than ±0.015°C/°C.
MAXIMUM LEAD RESISTANCE (each lead): 4 Wire: 50 ohms
3 Wire; 10 ohms
SENSOR CURRENT: 500µA maximum.
MODEL 868 and 869 GENERAL SPECIFICATIONS (unless specified):
DISPLAY: 3 1/2-digit LCD, 13mm (0.5") height. Polarity and decimal point indication.
CONVERSION RATE: 1.5 readings per second.
OVERRANGE AND OPEN SENSOR INDICATION: 3 least significant digits blanked.
1
MAXIMUM COMMON MODE VOLTAGE: 30VDC (42V peak AC).
COMMON MODE REJECTION: Less than 0.001°/ volt at DC, 50 Hz and 60 Hz. (100Ω
unblance, LO driven)
ENVIRONMENTAL LIMITS FOR OPERATING: -10° to 50°C (14° to 122°F), less than
80% relative humidity up to 35°C (95°F). Reduce R.H. Limit by 3% from 35° to 50°C
(1.7% R.H./°F from 95° to 122°F).
ENVIRONMENTAL LIMITS FOR STORAGE: -35° to 60°C (-30° to 140°F), less than
90% relative humidity up to 35°C (95°F); Reduce R.H. Limit by 3%/°C from 35° to
60°C (1.7% R.H./°F from 95° to 140°F).
INPUT CONNECTION: 4 pin miniature instrumentation connector.
POWER: 9V alkaline or carbon-zinc battery.
BATTERY LIFE, CONTINUOUS: 500 hours typical with alkaline battery; 300 hours
typical with carbon-zinc battery.
BATTERY INDICATOR: Display indicates "LO BAT' when less than 10% of life remains.
DIMENSIONS, WEIGHT: 160mm long x 69mm wide x 31mm thick (6.3" x 2.7" x 1.2").
Net weight 210gm (7.5 oz.)
CONSTRUCTION: Heavy duty ABS plastic housing.
ACCESSORIES SUPPLIED: Battery, instruction manual and mating input connector.
Specifications subject to change without notice.
2
GENERAL INFORMATION
The TEGAM Models 868 and 869 are handheld digital thermometers designed to use
100Ω platinum RTD temperature sensors for high accuracy and long term temperature
stability. The Model 868 has two switch-selectable ranges: from -199.9°F to + 199.9°F
with 0.1°F resolution, and between -360°F and +1100° with 1°F resolution. The Model
869 measures between -199.9°C and + 199.9°C with 0.1°C resolution, or between
-220°C and +630°C with 1°C resolution, or between -220°C and +630°C with 1°C resolution. Both instruments are designed for use with probes conforming to the DIN 43 760
standard.
Model 868 and 869 features include:
1. Platinum RTD Based Temperature Measurements. A chief advantage of the platinum
RTD (resistance temperature detector) sensor used by the unit is platinum's predictable resistance change with temperature, resulting in high accuracy.
2. Easily selected 3- or 4-Wire Measurements. The unit may be used with either 3-wire
or 4-wire temperature probes. An internal switch provides a means of easy 3- or 4wire selection (the unit is set for 4-wire operation at the factory).
3. Rugged Case. The instrument's case is made of high impact ABS plastic.
4. Long Battery Life. Because of low power consumption, an alkaline battery will typical-
ly last for 500 hours of continous operation.
MANUAL ADDENDA
Information presented in this manual was believed to be accurate at the time of printing.
Any changes in the instrument, which occur after this manual is printed, will be covered
separately in an addendum packed with the instrument. Be sure to note these changes
before attempting to operate or service the instrument.
OPTIONAL ACCESSORIES
Available accessories, including recommended temperature probes, are listed below.
Contact any TEGAM Distributor or the factory for information on purchasing accessories.
Model 8660 Tilt Stand/Belt Clip provides a convenient method of elevating the instrument to a convenient viewing height. The Model 8660 also includes a belt clip.
3
Model 8668 Soft Carrying Case provides protection for the Model 868 or 869 during
transportation or storage.
Model 8693 General Purpose Immersion Probe is a 4-wire 100Ω platinum RTD probe
designed for immersion in liquids as well as other general purpose applications. The
Model 8693 has a basic tolerance of ±0.3°C at 0°C. The measurement range of the
Model 8693 is -220°C to +630°C.
Model 8695 Surface Probe is a 4-wire 100Ω platinum RTD probe designed to measure
flat surfaces of solids in the range of -50°C to +260°C. The Model 8695 has a basic tolerance of ±0.3°C at 0°C.
Model 8696 Air/Gas Probe is a 4-wire 10012 platinum RTD probe with an exposed
sensor with an exposed sensor within a protective shroud to measure ambient temperature.The Model 8696 measures between -50°C and +260°C. The basic tolerance of the
Model 8696 is ±0.3°C at 0°C.
PREPARATION FOR USE
Carefully unpack the instrument from its shipping carton and inspect for any obvious
signs of physical damage. Report any damage to the shipping agent at once. The following items are included with every shipment:
1. Digital Thermometer
2. CD of Manual
3. 9V battery
4. 4-wire miniature instrumentation connector (mates with probe connector on the in-
strument).
NOTE:
As shipped, the instrument is configured for 4-wire
probes. See the operation section for selection of 3-wire
operation.
4
BATTERY
INSTALLATION/REPLACEMENT
A 9V battery is supplied with the unit. To install or replace the battery, proceed as follows:
WARNING
Turn off the power and disconnect the temperature
probe before removing the back cover to install or
replace the battery. Replace the back cover before
resuming use of the instrument.
1. Place the unit face down on a cloth-covered flat surface.
2. Remove the screws in the back cover; now remove the back cover by carefully
separating the two halves at the top of the instrument.
3. Place the 9V battery in the battery compartment as indicated in Figure 3, on page 7.
Be sure to observe proper polarity.
4. Re-install the rear cover on the instrument. Make sure the two case halves line up
properly; now secure the rear cover with the screws that were removed earlier.
5
OPERATION
Figure 1 shows the general control layout, including display nomenclature, for your
digital thermometer. The following paragraphs contain information on probe connection,
3- and 4-wire selection, range selection, and basic temperature measuring procedures.
Model 868 Model 869
Figure 1. Control and Display Nomenclature
1. Connect a temperature probe to the input connector on the top of the instrument. Use
one of the probes described in the accessories section; or install a 4-wire connector
on any 100 ohm platinum RTD probe using the information in Figure 2.
2. Make sure the instrument is set for 3-wire or 4-wire operation according to probe type
in use. The unit is set for 4-wire operation at the factory, but the mode of operation
may be changed as follows:
A. Remove the rear cover as described in the Battery Installation/Replacement
section of this manual.
B. Place the 3-wire/4-wire switch (see Figure 3) in the desired position.
6
Probe Input Connector
Low Battery Indicator
Shows when less than 10%
of battery life remains.
Minus Sign Indicates
Negative Temperature
1999 Count Display (Over-
range indicated by “1”
followed by blanked digits)
ON-OFF/Range Switch
100ΩΩPLATINUM RTD
αα
= 0.00385
RANGE:-220 C to 630 C
100ΩΩPLATINUM RTD
αα
= 0.00385
RANGE:-360 F to 1100 F
C. Re-install the rear cover and tighten the retaining screws.
REAR VIEW REAR VIEW
NOTE
Use only 100Ω platinum RTD sensors that conform to the DIN 43 760 standard
(alpha=0.00385). Other type sensors will give inaccurate results. Maximum allowable
lead resistance for rated accuracy is 50Ω per lead (4-wire) or 10Ω per lead (3-wire).
NOTE
For best accuracy, it is recommended that the instrument be used in the 4-wire
configuration with a suitable 4-wire probe. If 3-wire probes are used with the instrument
in the 4-wire mode, noisy readings will result (the displayed reading will jump around).
Unlike 4-wire, 3-wire reading accuracy is affected by changes in lead resistance,
and unbalanced lead wire resistance.
7
A. 4 TERMINAL
PROBE B. 3 TERMINAL
PROBE
SWITCH COVER
BATTERY
3 WIRE 4 WIRE SWITCH
Figure 3. 3-Wire/4-Wire Switch Location
Figure 2. 100 Ohm Platinum RTD Connections
3 WIRE
I
4 WIRE
J
Pin 1 Source +
Pin 2 Sense +
Pin 3 Source Pin 4 Sense -
3. Place the temperature range switch in the desired position. Use the lower range,
when possible, for best resolution and accuracy. Power is automatically turned on
when the range is selected.
4. Place the probe tip on or in the material to be measured.
WARNING
Do not subject the probe to a voltage more than 30V
RMS, 42V peak above earth ground, or a shock
hazard may result.
5. Take the reading from the display. The reading is in °F (Model 868) or °C (Model
869). Aleading minus sign indicates a negative temperature reading. An overrange
a "1" followed by blanked digits) may indicate the need to switch to a higher range,
or show that the temperature is outside the measuring range of the instrument, or
that the probe is open.
6. When the measurement is complete, place the on-off/range switch in the OFF position to conserve the battery.
ACCURACY CONSIDERATION
Model 868 basic accuracy is specified as on page 1. Similarily, Model 869 basic
accuracy is also specified on page 1. Keep in mind that these accuracy figures are for
4-wire probe operation with a lead resistance of less than 50Ω (each lead). Thus, 4-wire
probes should be used, whenever possible, to maintain the highest accuracy.
Accurate readings can also be made with the instrument in the 3-wire mode with a suitable 3-wire probe. For best accuracy, however, lead resistance should be no more than
10Ω per lead. Also, readings made in the 3-wire mode are sensitive to variations caused
by changes in lead resistance as well as to differences in lead resistance. For example,
a difference of only 38mΩ (0.038Ω) in lead resistance will cause a change of 0.1 °C
around 0°C. Four-wire readings are not affected by these lead resistance variations.
Accuracy figures do not include possible probe errors, which could affect overall measurement accuracy. Probe errors near 32°F for the Model 868, and near 0°C for the
Model 869, can be minimized by recalibrating the instrument for use with a specific
probe. For probe calibration procedures, refer to the calibration section of this manual.
8
The operating temperature of the instrument itself can affect accuracy. The accuracy figures given above are for an instrument operating in the range of 18°C to 28°C (65°F to
82°F). For operating environments between -10°C and 18°C (14°F and 65°F) and
between 28°C and 50°C (82°F and 122°F), a temperature coefficient of less than
±0.015°C/°C (±0.015°F/°F) can be expected.
SAFETY SYMBOLS AND TERMS
The symbol U
!
on the instrument denotes that the user should refer to the
operating instructions.
The WARNING used in this manual explains dangers that should result in personal
injury or death.
The CAUTION used in this manual explains hazards that could damage the
instrument.
WARNING
A shock hazard exists on the Instrument's input terminals when probes or sensors are
exposed to voltage levels greater than 30V rms or 42V peak.
9
WARNING
The information in this section is intended only for
qualified service personnel. Before removing the
back cover to service the instrument, disconnect
the temperature probe.
VERIFICATION PROCEDURE
Performance verification is performed by connecting known, precise resistors to the
instrument in place of a temperature probe and checking to see that the displayed
reading falls within a prescribed range. The following procedure should be performed at an ambient temperature between 18°C and 28°C (65°F and 82°F) at a relative humidity of less than 80%. If the instrument has been stored outside these limits, allow at least 24 hours for operating conditions to stabilize.
Required Equipment:
Precision decade resistance, ±0.01% tolerance
(Gen Rad Model 1433T or equivalent)
Female 4-wire instrumentation connector (supplied with instrument).
NOTE
The following procedure must be performed with the instrument in the 4-wire mode. See Figure 3 for the location
of the 3-wire/4-wire switch which sets the appropriate
mode. Access to the switch requires rear cover removal
as described in the disassembly instructions.
Procedure:
1. Connect the precision resistance box to the instrumentation connector as shown in Figure 4. Plug the connector into the instrument.
2. Turn on the instrument and verify that the LO BAT indicator is not
displayed; if it is, replace the battery before beginning the verification
procedure.
10
Figure 4. Connections for Performance Verification and Calibration
3. Refer to Table 1, which lists the verification procedure for both in-
struments covered by this manual. To verify instrument performance at each of the points, set the resistance box to the required
value; with the instrument on the prescribed range, verify that the
displayed reading falls within the necessary limits.
4. If the displayed reading is out of tolerance at any of the points, refer
to the calibration section for the correct procedure to bring the instrument within tolerance.
NOTE
If the instrument is still under warranty (less than 12
months since the date of shipment), and it does not meet
specifications after calibration, contact your TEGAM Distributor or the factory to determine the correct course
of action.
Table 1. Performance Verification Procedure
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REAR VIEW
DECADE RESISTANCE BOX
Model 868
Range
Resistance
Value
Allowable Reading
(65°F to 82°F)
1100°F
200°F
200°F
200°F
200°F
1100°F
10.81
ΩΩ
71.00
ΩΩ
93.03
ΩΩ
114.68
ΩΩ
134.92
ΩΩ
311.56
ΩΩ
-364 to -356
-100.4 to -99.6
-0.4 to +0.4
99.6 to 100.4
194.6 to 195.4
1098 to 1102
Table 1. Performance Verification Procedure (Cont.)
CALIBRATION
Calibration should be performed yearly or whenever the instrument is
known to be out of specification. Calibration should be done at an ambient temperature of 23±1 °C at a relative humidity of less than 80%.
Normal instrument calibration is performed by substituting precision
resistors of known value for the temperature probe and adjusting
calibration potentiometers for specified readings on the display. The
instrument may also be calibrated to compensate for probe errors near
0°C (32°F). Both procedures are covered in this section.
Calibration Equipment:
Gen Rad precision decade resistor box, ±0.01% tolerance,
(Model 1433T or equivalent).
Female 4-wire instrumentation connector (supplied with instrument).
The following items are necessary only for probe compensation:
Distilled ice water bath in Dewar flask or thermos.
Platinum RTD immersion probe (Model 8693 or equivalent).
12
Model 869
Range
Resistance
Value
Allowable Reading
(65°F to 82°F)
630°C
200°C
200°C
200°C
200°C
630°C
9.90
ΩΩ
60.26
ΩΩ
100.00
ΩΩ
138.51
ΩΩ
174.01
ΩΩ
313.71
ΩΩ
-222 to -218
-100.3 to -99.7
-0.3 to +0.3
99.7 to 100.3
194.7 to 195.3
599 to 601
SWITCH COVER
CALIBRATION
ADJUSTMENTS
BATTERY
TERMINALS
BATTERY
ADJUSTMENT ORDER 1. R104
2. R105
3. R103
R103
R104
R105
Figure 5. Calibration Adjustment Locations
GENERAL INSTRUMENT CALIBRATION
1. Connect the precision decade resistor box to the instrument as
shown in Figure 4.
2. Remove the rear cover as described in the battery installation/replacement
section of this manual. Note that it is not necessary to remove the PC
board to perform calibration.
3. Check to see that the 3-wire/4-wire switch is in the 4-wire position.
4. Turn on the instrument power and verify that the LO BAT indicator
is not displayed. If it is, replace the battery before beginning the
calibration procedure.
5. Refer to Table 2. Calibration procedures are outlined there. Per-
form each step in the procedure in the order shown by setting
the decade box to the precise value listed and then adjusting the
associated calibration potentiometer for the required reading on
the display. Potentiometer locations are shown in Figure 5.
6. If probe compensation is required, proceed to the next paragraph;
otherwise dismantle the test fixture, set the 3-WIRE/4-WIRE switch
to the correct position and replace the back cover.
Table 2. Calibration Procedure
PROBE COMPENSATION CALIBRATION
The procedure outlined in the last paragraph provides accurate absolute
instrument calibration, but it cannot compensate for probe inaccuacy.
13
Model 868
Step
Adjustment
Potentiometer
Range
1
2
3
R104
R105
R103
200°F
200°F
1100°F
Calibration
Resistor
Value
93.03
ΩΩ
113344..9922 ΩΩ
331111..5566 ΩΩ
Desired
Reading
00.0
195.0
1100
Model 869
Step
Adjustment
Potentiometer
Range
1
2
3
R104
R105
R103
200°C
200°C
630°C
Calibration
Resistor
Value
100.00
ΩΩ
117744..0011 ΩΩ
331133..7711 ΩΩ
Desired
Reading
00.0
195.0
600
Probe errors near 0°C (32°F) can be minimized by using the following procedure.
1. Make up an ice water bath by firmly packing a Dewar flask or thermos
with pea-size ice cubes made of distilled water and then filling the container
with distilled water. Replace melted ice with new ice while removing excess
water during the calibration procedure.
2. Connect the probe to be compensated to the instrument.
3. Drill a hole in the flask or thermos cap just large enough to accomodate
the probe. Place the cap on the bath container and pass the probe through
the hole until the probe tip rests at the center of the ice water bath.
4. Allow 20 minutes for the test fixture temperature to stabilize. With the Model
868 on the 200°F range, adjust R104 for a reading of 32.0 on the display. For
the Model 869, R104 should be adjusted for a reading of 00.0 with the instrument
on the 200°C range.
NOTE
Using this method of probe calibration will uncalibrate the
instrument slightly when used with other probes.
14
WARRANTY
TEGAM, Inc. warrants this product to be free from defects in material and
workmanship for a period of one year from date of shipment. During the warranty period, we will at our option, either repair or replace any product that
proves to be defective.
TEGAM, Inc. warrants the calibration of this product for a period of one year
from date of shipment. During this period we will recalibrate any product that
does not conform to the published accuracy specification.
To exercise this warranty, contact TEGAM, Inc., Ten Tegam Way, Geneva,
Ohio 44041/FAX (440) 466-6110/ (440) 466-6100, M-F, 8 a.m.-5 p.m. ET. You
will be given prompt assistance and return instructions. Send the instrument,
transportation prepaid, to the indicated service facility. Repairs will be made
and the instrument returned, transportation prepaid. Repaired products are
warranted for the balance of the original warranty, or at least 90 days,
whichever is longer.
LIMITATION OF WARRANTY
TEGAM, Inc. warranty does not apply to defects resulting from unauthorized
modification or misuse of any product or part. This warranty also does not
apply to fuses, batteries, or damage from battery leakage.
This warranty is in lieu of all other warranties, expressed or implied, including
any implied warranty of merchantability or fitness for a particular use.
TEGAM Inc. shall not be liable for any indirect, special or consequential damages.
STATEMENT OF CALIBRATION
This instrument has been inspected and tested in accordance with specifications
published by TEGAM, Inc.
The accuracy and calibration of this instrument are traceable to the National
Institute of Standards and Technology through equipment which is calibrated
at planned intervals by comparison to certified standards maintained in the
Laboratories of TEGAM, Inc.
15
TEGAM is a manufacturer of electronic test and measurement equipment for metrology, calibration, and production test. We also provide repair, calibration, and other support services for a wide variety of test and measurement equipment including RF power
sensor calibration systems, RF attenuation measurement systems, resistance
standards, ratio transformers, arbitrary waveform generators, micro-ohmmeters,
LCR meters, handheld temperature calibrators, thermometers, humidity and
temperature control devices, and more.
TEGAM also repairs and calibrates test and measurement equipment formerly manufactured by Electro-Scientific Industries (ESI), Gertsch, Keithley Instruments, Lucas
Weinschel, and Pragmatic Instruments. A complete list can be viewed on our Product
Service Directory at www
.tegam.com.
For more information about TEGAM and our products, please visit our website at
www
.tegam.com; or contact one of our customer service representatives at
sales@tegam.com or 800-666-1010.
TEN TEGAM WAY GENEVA, OHIO 44041
PHONE 440-466-6100 FAX 440-466-6110
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