Tegam 840A User manual

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840A, 845, 850, 855
Digital Temperature Calibrator - Thermometer
MODEL 840A, 845, 850, 855
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.
Instruction Manual
PN# 840A-901-01CD
Publication Date: November 2019
REV. M

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TABLE OF CONTENTS
TABLE OF CONTENTS
General Information
Common Specifications ...................................................................... .................... 1
Unique Specifications .............................................................................................. 4
Features ............................................................................................................... 5
Manual Addenda .................................................................................................... 5
Unpacking and Inspection ....................................................................................... 6
Safety Information ................................................................................................. 6
Safety Precautions ................................................................................................. 6
Battery Installation/Replacement ..............................................................................8
Memory Backup .................................................................................................... 9
Operation with Rechargeable Battery....................................................................... 9
Operating Instructions ............................................................................................ 9
1. Diagnostics and Error Messages .................................................................... 9
2. Initial Turn On .......................................................................................... 11
3. Meter Mode Operation (Thermocouple) ........................................................ 12
4. Meter Mode Operation (RTD, Thermistor, Ohms) ........................................... 12
5. Data Logging & Recall ............................................................................... 14
6. Calibrator Mode Operation (Thermocouples) ................................................. 16
7. Calibrator Mode Operation (RTD, Thermistor, Ohms) ...................................... 17
8. Storage and Recall of Calibrator Settings ..................................................... 19
9. Step Function ........................................................................................... 20
10. Ramp Function ........................................................................................ 20
Service Information
1. Calibration Procedures ............................................................................... 21
A. Thermocouple Calibration ...................................................................21
B. Resistance Calibration ........................................................................26
2. Calibration Verification ............................................................................... 30
3. Mechanical Parts Diagram .......................................................... ............. .. 36
Warranty................................................................. .......................................... 37
Limitation of Warranty.......................................................................................... 37
Statement of Calibration .......................................................................... .............37
MAINT E N A NCE INST RUCT IONS W I T H I N T HIS M ANUA L A R E F O R US E B Y QUA L I F IED SE RVICE
P E RSO NN EL O N L Y .
D O NO T AT T E MPT ANY S E R V I C I N G OTH E R THAN THAT CO NTAIN E D IN T H E O P E R ATI O N
INST
RUC T IONS UNLE SS Y O U ARE QUALIFIE D T O D O SO .

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GENERAL INFORMATION
GENERAL INFORMATION
This manual provides operating instructions and maintenance information for four temperature
instruments. These instruments are high performance calibrator-thermometers capable of
simulating and measuring a wide-variety of sensors. In addition, features such as data storage
and ramping further enhance their versatility.
It is recommended that you read this manual thoroughly, especially the sections on safety, prior
to operating these instruments.
COMMON SPECIFICATIONS
THERMOMETER INPUTS: THERMOCOUPLE; Miniature TC jack. RTD, OHMS, THERMISTOR; T-
series instrumentation connector.
CALIBRATOR OUTPUTS: THERMOCOUPLE; Miniature TC jack. RTD, OHMS, THERMISTOR; T-
series instrumentation connector.
THERMOCOUPLE TYPES: K, J, T, E, N, B, R, S, G, C, D.
RTD TYPES: 100Ωplatinum (α= 0.00385)
1000Ωplatinum (α= 0.00385)
THERMISTOR TYPE: 2252Ω(YSI Series 400).
RANGES: K; -200°C to 1372°C, -328°F to 2502°F
J; -210°C to 760°C, -346°F to 1400°F
T; -200°C to 400°C, -328°F to 752°F
E; -230°C to 1000°C, -382°F to 1832°F N; -200°C to 1300°C, -328°F to 2372°F
B; 500°C to 1820°C, 932°F to 3308°F R; 0°C to 1768°C, 32°F to 3214°F
S; 0°C to 1768°C, 32°F to 3214°F
G; 300°C to 2316°C, 572°F to 4201 °F C; 0°C to 2316°C, 32°F to 4201 °F
D; 0°C to 2316°C, 32°F to 4201 °F RTD; -200°C to 850°C, -328°F to 1562°F
THERMISTOR; -40°C to 150°C, -40°F to 302°F
OHMS; 0-999.99
Ω
0-9,999.9
Ω
0-99,999
Ω
ACCURACY: All stated accuracies are exclusive of sensor errors and lead resistance induced
errors. Refer to 'UNIQUE SPECIFICATIONS' for detail accuracy specs.
RESOLUTION: TEMPERATURE; 0.1 °/1° F/C
OHMS; 0.01Ω/0.1Ω/1Ω

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GENERAL INFORMATION
REPEATABILITY (1 week at constant ambient temperature):
K, J, T, E, N; ±0.2°F typ.
B, R, S, G, C, D; ±1.0°F typ.
RTD, THERMISTOR; ±0.1 °F typ.
OHMS; ±0.01 % rdg typ.
METER-MODE INPUT-CURRENT (THERMOCOUPLES): 50nA typ.
METER-MODE READING-RATE: 1 reading/second typ.
METER-MODE EXCITATION-CURRENTS:
100ΩRTD; <2mA
1000ΩRTD; <200
μ A
999.99Ω; <2mA
9999.9Ω; <200
μ A
99999Ω; <50
μ A
THERMISTOR; T ≤113°F <50
μ A
T> 113°F, <2mA
CALIBRATOR MODE OUTPUT LOAD (THERMOCOUPLES): 500Ωmin.
CALIBRATOR-MODE EXCITATION-CURRENTS:
100ΩRTD; 0.5 - 1mA (0.1 - 2mA typ.)
1000ΩRTD; 50 - 100μA (10-200μA typ.)
999.99Ω; Same as 100ΩRTD
9999.9Ω; Same as 1000ΩRTD
99999Ω; 10 - 20μA (1 - 20μA typ.)
THERMISTOR; T ≤113°F, 10 - 20 μ A
T> 113°F, 0.5- 1mA
MAXIMUM COMMON MODE VOLTAGE: 42V peak to earth.
KEYPAD: 12 momentary switches with tactile feedback select;
• On/Off
• Change/Enter
• Clear/-0
• Sensor Select/1
• °F/°C/2
• Resolution/3
• Operate/4
• Store/5
• Recall/6
• Calibrator/Meter/Up Ramp/7
• Calibrator Step/Down Ramp/8
• Calibrator Ramp/Meter Hold/9

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GENERAL INFORMATION
DISPLAY: 5 digit LCD, 0.4" height, polarity indication and decimal point. Annunciators;
• Loaded Memory Locations (10 for data storage, 4 for ramp parameters)
• Low Battery (BAT)
• Number Change Mode (NUM)
• Calibrator Mode (CALIB)
• Meter Mode (METER)
• Operate Mode (OPR)
• Store Mode (STO)
• Recall Mode (RCL)
• Meter Hold (HOLD)
• Scale (°F/°C)
• Sensor Type
POWER OFF CONFIGURATION RETENTION: Instrument retains last selected;
• Sensor Type
• °F/°C Scale
• 0.1°/1° Resolution
• Calibrator/Meter Mode
• Memory Contents (data storage and ramp parameters).
DIAGNOSTICS: Display codes indicate following conditions;
• 'BAT': Low Battery
• 'OPEN': Open Input Thermocouple, RTD or Thermistor.
• 'E-1' (momentary): Invalid Keypad Entry
• 'E-2' (momentary): Ramp Function Not Installed
• 'HI': Temperature Reading or Keypad Entry Exceeds Rating
• 'LO': Temperature Reading or Keypad Entry Too Low For Accuracy
• LCD Test: During power-up, all segments and annunciators enabled momentarily
ENVIRONMENTAL LIMITS FOR OPERATING: 0°C to 50°C, less than 90% relative humidity
(R.H.) up to 35°C; reduce R.H. limit by 3%/°C from 35°C to 50°C.
ENVIRONMENTAL LIMITS FOR STORAGE: -35°C to 60°C, less than 95% relative humidity
(R.H.) up to 35°C; reduce R.H. limit by 3%/°C from 35°C to 60°C.
POWER: 9 volt alkaline battery (NEDA 1604A).
BATTERY LIFE, CONTINUOUS: 10 hrs. typical, alkaline; 3 hrs typical, Ni-Cd (rechargeable).
BATTERY INDICATOR: Display indicates BAT when less than 10% of life remains.
DIMENSIONS, WEIGHT: 7.0" x 2.9 x 1.1". Net weight 12 oz.

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GENERAL INFORMATION
UNIQUE SPECIFICATIONS
NOTE: The specifications below are specific to the model(s) as identified by
model number. The difference specifications are in addition to the
'COMMON SPECIFICATIONS' found on pages 2-4.
• MODEL 840A:
SENSOR SELECTION: K, J, T Thermocouples
ACCURACY: (18°C to 28°C ambient, 2 years):
K, J, T; ±0.5°F (rdg ≥-50°F).
±0.04% rdg (rdg > 1250°F)
±1.0°F (rdg < -50°F)
TEMPERATURE COEFFICIENT: From 0°C to 18°C, and 28°C to 50°C;
less than ±(0.006% rdg +0.03°C)/°C.
RAMP FUNCTION: Not Included.
BATTERY LIFE, CONTINUOUS: 16 hrs typical, alkaline; 4 hrs typical, Ni-Cd (rechargeable).
• MODEL 845:
SENSOR SELECTION: K, J, T, E, N, B, R, S, G, C, D Thermocouples
ACCURACY: (18°C to 28°C ambient, 2 years):
K, J, T, E, N; ±0.5°F (rdg ≥-50°F)
±1.0°F (rdg < -50°F)
B, R, S, G, C, D; ±1.7°F
TEMPERATURE COEFFICIENT: From 0°C to 18°C, and 28°C to 50°C;
K, J, T, E, N; ±(0.002% rdg + 0.03°C)/°C
B, R, S, G, C, D; ±(0.002% rdg + 0.1°C)/°C
RAMP FUNCTION: Included.
BATTERY LIFE, CONTINUOUS: 16 hrs typical, alkaline; 4 hrs typical, Ni-Cd (rechargeable).
• MODEL 850:
SENSOR SELECTION: K, J, T, E Thermocouples
100ΩPlatinum RTD
2252ΩThermistor
1,000Ω/100,000ΩResistance
ACCURACY: (18°C to 28°C ambient, 2 years):
K, J, T, E; ±0.5 °F (rdg ≥-50°F).
±0.04% rdg (rdg > 1250°F)
±1.0°F (rdg <-50°F)
OHMS; ±0.04% range
RTD; ±0.2°F (rdg≥- 50°F) (Calibrator mode)
±0.5°F (rdg < - 50°F) (Calibrator mode)
±0.2°F ±0.04% rdg (rdg ≥ -50°F) (meter mode)
±0.5°F±0.04% rdg (rdg < -50°F) (meter mode)
Thermistor; ±0.5°F
TEMPERATURE COEFFICIENT: From 0°C to 18°C, and 28°C to 50°C;
K, J, T, E; ±(0.006% rdg + 0.03°C)/°C
RTD, THERMISTOR, OHMS; ±(0.006% rdg +0.012% rng)/°C
RAMP FUNCTION: Not Included.

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GENERAL INFORMATION
• MODEL 855:
SENSOR SELECTION: K, J, T, E, N, B, R, S, G, C, D Thermocouples
100Ω/1000ΩPlatinum RTD
1,000Ω/10,000ΩResistance
ACCURACY: (18°C to 28°C ambient, 2 years):
K, J, T, E, N; ± 0.5°F (rdg ≥-50°F)
±1.0°F (rdg < -50°F)
B, R, S, G, C, D; ±1.7°F
RTD; ±0.2°F (rdg ≥- 50°F) (Calibrator Mode)
±0.5°F (rdg < - 50°F) (Calibrator Mode)
±0.2°F ±0.04% rdg (rdg ≥ -50°F) (meter mode)
±0.5°F ±0.04% rdg (rdg < -50°F) (meter mode)
OHMS; ±0.02% range
TEMPERATURE COEFFICIENT: From 0°C to 18°C, and 28°C to 50°C;
K, J, T, E, N; ±(0.002% rdg + 0.03°C)/°C
B, R, S, G, C, D; ±(0.002% rdg + 0.1°C)/°C
RTD, OHMS; ±(0.002% rdg + 0.004% rng)/°C
RAMP FUNCTION: Included.
FEATURES
•Combination calibrator, thermometer and datalogger.
•Function selection and numeric data entered via 12 keyswitch color coded keypad.
•Keyswitches have tactile feedback.
•5 digit LCD includes annunciators for operating modes.
•Up to 11 thermocouple types, 2 RTD types, and thermistor.
•1° or 0.1° resolution over temperature range of each sensor.
•°F and °C scales.
•Reading hold mode.
•10 memory locations for saving meter readings and/or calibrator outputs.
•Step mode for quick sequential recall of calibrator outputs from memory.
•Manual/automatic ramping for testing controller setpoints.
•Conforms to ITS-90 thermocouple & RTD tables. Refer to 'Service Information' (page 23) for
more information.
•Dust proof, splash proof, drop proof construction.
•Built-in tilt stand/hanger for bench use or hands free field measurements.
•User friendly programming.
•Retains data and programming, even when turned off.
•Performs diagnostic tests and indicates fault conditions.
•Low battery and open sensor indications.
MANUAL ADDENDA
Improvements or changes to this manual will be explained on an addendum included with the
instrument. All change information should be incorporated immediately into the appropriate
places in the manual.

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GENERAL INFORMATION
UNPACKING AND INSPECTION
Each instrument is inspected both mechanically and electrically before shipment. Upon receiving
your instrument unpack all items from the shipping container and check for any obvious damage
that may have occurred during transit. Report any damage to the shipping agent. Retain and use
the original packing materials if reshipment is necessary.
SAFETY INFORMATION
SAFETY SYMBOLS AND TERMS
The symbol on the instrument denotes that the user should refer to the operating
instructions.
The WARNING used in this manual explains dangers that could result in personal injury or
death.
The CAUTION used in this manual explains hazards that could damage the instrument.
SAFETY PRECAUTIONS
WARNING
These instruments are intended for use by qualified
personnel trained in the safe operation of electronic testing
equipment. Read the instruction manual thoroughly before
using, to become familiar with the instrument's operations
and capabilities.
WARNING
Do not touch a temperature probe sheath when measuring
excessively high or low temperatures, or toxic substances.
WARNING
Do not attempt to measure temperatures beyond the range
of the probe being used. Probe damage or personal injury
could result from exceeding a probe's maximum
temperature rating.
WARNING
Do not substitute a metal part for the nylon screw in the rear
case. Doing so will degrade electrical isolation of the case.

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GENERAL INFORMATION
WARNING
The American National Standards Institute (ANSI) states that
a shock hazard exists when probes or sensors are exposed
to voltage levels greater than 42VDC or 42V peak AC. Do
not use this instrument where voltages at the measurement
surface exceed these levels.
WARNING
The battery is accessible through a cover on the back of the
instrument. To avoid electrical shock hazard, disconnect all
temperature probes and sensors and turn the unit off before
removing the cover.
WARNING
Never use this instrument or any probe or sensor inside a
microwave oven.
CAUTION
Avoid making sharp bends in probe or sensor lead wires.
Bending lead wires at a sharp angle can damage the wire
causing probe failure.
CAUTION
Keep inputs electrically isolated from outputs. Do not
connect an external voltage source between the two
connectors, and avoid any external electrical pathways
between input and output (T2 & T1).
Failure to do so will disturb meter readings and calibrator
output levels. Damage to the instrument is also possible.
Where the meter and calibrator connectors are
simultaneously wired into a system lacking the above
isolation, it is necessary to use an "ungrounded" (i.e.
electrically isolated) probe at the thermometer input.

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GENERAL INFORMATION
BATTERY INSTALLATION/REPLACEMENT
A 9V alkaline battery is supplied with the instrument but not installed. Read the following
installation instructions before attempting to install or remove the battery. Replacement batteries
should also be alkaline types.
WARNING
Turn the unit off and disconnect any input/output
connections before replacing the battery. Put the cover
back into place on the battery compartment before
resuming use of the instrument.
1. Remove the cover from the battery compartment by sliding it off in the direction of the
arrow located on the battery cover.
2. Remove the old battery.
3. Place the new battery in the battery compartment. Be sure to observe proper polarity.
4. Re-install the battery cover before resuming use of the instrument.
Figure 1. Battery Installation
NOTES:
• Less than 10% of battery life remains when the BAT annunciator turns
on.
• When the battery is excessively discharged, the display is blanked.
• If the instrument is going to be stored for a long period of time or in a
high temperature environment, remove the battery to prevent leakage
damage.
• After a new battery is installed, allow approximately 5 seconds
for display turn-on the first time the unit is turned on. During
this period, microcomputer initialization is performed.

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GENERAL INFORMATION
MEMORY BACKUP
During battery replacement, the contents of user-programmed memory (data, operating modes,
etc.) can be saved. Prior to removing the old battery, turn off the instrument, and connect a
Model 80010 battery charger. Then exchange batteries, and disconnect the battery charger. Do
not leave the battery charger connected to instruments with non-rechargeable batteries.
OPERATION WITH RECHARGEABLE BATTERY
Model 80010 provides a 9-volt Ni-Cd battery and recharger suitable for use with the unit. This
battery provides 3-4 hours of continuous operation.
NOTE: Instrument accuracy is degraded while recharging the Ni-Cd battery, and
published specifications do not apply to measurements made during
recharging.
Turn off the instrument to recharge the battery. Allow 7 hours to recharge the battery fully. Then
unplug the recharger to avoid overcharging. Allow 20 minutes after charging before taking
measurements.
MODEL 80010 SPECIFICATIONS
Model 80010/100 80010 80010/220
Vin:
90-110 VAC
108-132 VAC
198-242 VAC
50/60 Hz
50/60 Hz
50/60 Hz
Vout: 40 VDC @ 5mA 40 VDC @ 5mA 40 VDC @ 5mA
OPERATING INSTRUCTIONS
1. DIAGNOSTICS AND ERROR MESSAGES
Unit self-diagnostics provide fault condition readouts which are described below:
PROBLEM: LIKELY CAUSE:
Blank display, unit does not power-up. (1) Improper battery installation.
Check battery polarity.
(2) Dead battery.
BAT Annunciator. (1) Low battery voltage, install a new
battery. If problem persists, consult
factory.
Display reads OPEN. (1) No thermocouple, RTD or thermistor
is plugged into the meter input.

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GENERAL INFORMATION
Display reads E1 momentarily. (1) This indicates that an invalid keypad
entry has been made. Review keystroke
sequence, or consult manual for input
instructions.
Display reads E2 momentarily. (1) Attempt made to activate non-
installed ramp function.
NOTE: RAMP Function enabled on Models 845 and 855 only.
Display reads HI. (1) Meter-mode input-temperature
exceeds rating of selected sensor.
(2) Calibrator-mode keypad-entry
exceeds rating of sensor type.
Display reads LO. (1) Meter-mode input-temperature
too low for accurate measurement.
(2) Calibrator-mode keypad-entry too
low for accurate simulation.
Figure 2. Keypad

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GENERAL INFORMATION
Figure 3. Display Test
2. INITIAL TURN ON
Turn on the instrument by depressing the ON-OFF keyswitch once (Figure 2). At power-up, the
unit first performs a display test. All segments and annunciators of the liquid crystal (LCD) are
momentarily turned on for visual confirmation by the user (Figure 3).
NOTE: In case of missing or poor-contrast segments, contact factory.
If the unit is turning on for the first time after a new battery is installed, it will automatically
default to the METER mode (ie. temperature measurement operation). It also defaults to K-type
thermocouples, and °F readings with 0.1° resolution. The corresponding LCD annunciators are
enabled:
METER : (Unit functioning as a thermometer)
K : (K-type thermocouple)
°F : (Fahrenheit readings)
OPR : (Instrument is operational)
If no input thermocouple is connected to the unit at this time, the numeric segments will indicate
"OPEN".
Plugging a thermocouple into the meter jack (connector T2, on the top right side) will give actual
thermocouple temperature readings.
NOTE: To obtain full accuracy, allow 1-2 minutes after connecting a
thermocouple plug, for thermal setting.
If the instrument is to be used as a thermometer or ohmmeter, refer to the Meter Mode Operation
section for detailed instructions. For use as a temperature-calibrator or ohms simulator, refer to
Calibrator Mode Operation.

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GENERAL INFORMATION
3. METER MODE OPERATION (Thermocouples) Set-Up:
1. Turn on instrument by depressing the ON/OFF key.
2. Check that the BAT annunciator turns off following the power-up LCD test.
If it does not turn off, less than 10% of battery remains. Refer to Battery Installation/Replacement
instructions.
3. If the meter is already in the METER mode, the METER annunciator will
be on. Otherwise the calibrator mode is enabled and the CALIB annunciator is on. Depress the
METER key to return to meter mode.
4. Connect an input thermocouple (TC) to connector T2. Select the appropriate TC Type with the
select-key. A display annunciator will indicate the selected TC-type.
NOTE: Space and legibility constraints on the display preclude the use of
dedicated annunciators for the less common tungsten- rhenium
thermocouple types (G, C & D). Instead, these types are annunciated
momentarily on the alpha-numeric display when first selected. Both T
and R annunciators remain on to indicate a Tungsten-Rhenium
selection. To recall the actual G, C, D selection, turn the unit off, then
on again for another momentary readout.
5. Select temperature scale with °F/°C key. The corresponding annunciator is enabled.
6. Select display resolution with 0.0.1 key.
NOTE: Set-up is retained during power-off.
Hold:
Meter readings can be put on hold at any time by depressing the HOLD key. At this time,
the HOLD annunciator turns on, the reading is frozen, and all keys (except ON/OFF and
HOLD) are locked out. Depress the HOLD key again to return to real-time readings, and
re-enable the keypad.
4. METER MODE OPERATION (RTD, Thermistor & Ohms) Set-Up:
1. Connect a sensor or unknown resistance to the instrument as shown in Figures 4, 5, or 6.
The 2-wire configuration is simplest, but includes lead-wire resistance in the measurement. 2-wire
measurements are generally limited to high resistance sensors (e.g. 1000-ohm RTDs, 2252-ohm
thermistors).
Lead resistance errors are compensated for in 3-wire configurations. However, full
compensation requires equal resistance in each lead. This configuration is common with 100-
ohm RTDs.

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GENERAL INFORMATION
In 4-wire configurations, accuracy is unaffected by lead resistance and resistance differences
between leads.
NOTE: These instruments measure input voltages on all 4 terminals, and are able
to distinguish between 2-4 and 3-wire hookups. Switching between these
measurement modes is automatic.
2. Set instrument to METER mode.
3. Use the Sensor-Select key to set the instrument to the appropriate function and range.
NOTE: Due to limited display area, 100Ωand 1000ΩRTD's are indicated on
the display by a momentary readout of "RTD-100" (or "RTD-1000")
when first selected.
Thermistors are identified by a momentary alpha-numeric readout of "Y-
400" (signifying YSI Series-400 type thermistor).
Any of these readouts can be recalled by turning the unit off and back
on.
(RTD, Thermistor, etc.)
Figure 4. 2-Wire Resistance Measurement
Figure 5. 3-Wire Resistance Measurement

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GENERAL INFORMATION
Figure 6. 4-Wire Resistance Measurement
5. DATA LOGGING AND RECALL
Operating as a meter, the unit can save and recall up to 10 readings (each with independent
parameters: eg. °F/°C, TC-type and resolution) in random access memory.
To Save Readings:
1. While in the METER OPR mode, depress the STORE key. Note that the OPR annunciator is replaced
by STO.
2. Next depress one of the memory location numbers (keys 0, 1, ..., 9). The corresponding
memory annunciator turns on and the meter returns momentarily to the OPR mode, displaying
thermocouple temperature.
eg. STORE 7
NOTES:
• The enabled location annunciator indicates that the meter reading
at the instant that the location number key was pressed, was stored in
memory.
• When data is stored in a location already filed with data, the new data
replaces the old.
• Stored readings are retained during power-off.
To Recall Readings:
1. While in the METER OPR mode, readings stored earlier can be displayed by first depressing the
RECALL key. Note that the OPR annunciator is replaced by RCL, and all memory location

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GENERAL INFORMATION
annunciators are blanked.
2. Next depress the keypad number corresponding to the desired location.
Note that the annunciator for this location turns on and the memory contents are displayed.
3. Several stored readings can be randomly recalled by a key sequence such as:
eg. RECALL 3
RECALL 5
RECALL 2 etc.
4. To return the meter to the operate mode, depress OPR after recalling the last reading. All
active location annunciators will turn on again, together with the OPR annunciator.
NOTE: Recalling data from unused (i.e. empty) locations will give a zero
reading.
To Erase Data Locations (Meter Mode):
1. Individual data locations can be erased by recalling the location to be cleared, followed by a
CLEAR key input. Note that the annunciator for the cleared location is turned off,and the meter
returns to OPR.
eg. RECALL 3
CLEAR
NOTE: There is no need to clear a location if new data is ready for saving in this
location. Just STORE the new data. It will write over and delete the old.
Figure 7.

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GENERAL INFORMATION
6. CALIBRATOR MODE OPERATION (Thermocouples) Set-Up:
1. Turn on the instrument by depressing the ON/OFF key.
2. Check that the BAT annunciator turns off after display check. If not, refer to Battery
Installation/Replacement instructions.
3. When operating as a calibrator, the display indicates CALIB. Should the instrument be
in the METER mode, press the CALIB key to change to the calibrator function.
4. Select the thermocouple type that will be used.
NOTE: Space and legibility constraints on the display preclude the use of
dedicated annunciators for the less common tungsten-rhenium
thermocouple types (G, C, & D). Instead, these types are
annunciated momentarily on the alpha-numeric display when first
selected. Both T and R annunciators remain on to indicate a
Tungsten-Rhenium selection. To recall the actual G, C, D selection,
turn the unit off, then on again for another momentary readout.
5. Select the desired temperature scale (°F/°C key).
6. Select the resolution desired (0.0.1 key).
NOTE: With 1° resolution, one less key stroke will be required to enter
calibrator output temperatures via the keypad.
7. The unit accepts numeric inputs by first changing the keypad to its number-entry mode (NUM)
by depressing the CHANGE/ENTER key once.
The numeric display will flash, the OPR annunciator will turn off, and the NUM annunciator will
turn on. Key in desired temperature value, most significant digit first. After the desired
temperature value is keyed in, press CHANGE/ENTER to return to OPR mode.
To enter a value of 212° with 0.1° resolution, the following keystrokes are used:
CHANGE/ENTER, 2, 1, 2, 0, CHANGE/ENTER
NOTES:
• Invalid numeric entries (eg. a temperature beyond the span of the
selected TC type) will cause a corresponding error code to be
displayed.
• To enter negative (ie. minus) temperatures, press the -0 key first
when in the NUM mode. The first press on this key enters the negative
sign. Subsequent presses enter zeros.
•To correct a numeric entry while in the NUM mode, press the
CHANGE/ENTER key twice. This will return number entry to the
beginning of a new number.

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GENERAL INFORMATION
• To return the calibrator output to 0° while in the OPR mode, press
the CLEAR key.
• The unit can be used as a convenient °F to °C or °C to °F calculator.
For example, to convert 77°F to a Celsius reading, go to the CALIB OPR mode, enter the reading
to be converted, and change scale.
eg.°F
CHANGE/ENTER
77
CHANGE/ENTER
°C (Display reads 25°C)
7. CALIBRATOR MODE OPERATION (RTD, Thermistor & Ohms)
NOTE: The 850/855 requires a steady current to function properly in the
calibration mode. Some transmitters operate with a pulsating current
which won't work with the 850/855. These devices are normally provided
with a calibration mode which when enabled stops sending pulsating
current and supplies a steady current. Disabling the mode returns the
transmitter to its normal operating state.
Set-Up:
1. Connect measurement equipment under test (eg. RTD thermometer, ohmmeter etc.) to the
instrument as shown in Figures 8, 9, or 10.
The same performance tradeoffs apply to 2, 3 and 4-wire simulations as to 2, 3, and 4-wire
measurements. Refer to RTD, Thermistor and Ohms Meter-Mode section above for wiring
guidelines.
2. Set instrument to CALIBRATOR mode.
3. Use the sensor-select key to set the instrument to the appropriate function and range.
Figure 8. 2-Wire Resistance Simulation

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GENERAL INFORMATION
Figure 9. 3-Wire Resistance Simulation
Figure 10. 4-Wire Resistance Simulation
NOTE: To ensure accurate calibrator outputs, observe specified limits to
excitation currents. If in doubt, check current levels with a DMM in
series with either source lead (1 or 3).
NOTE: Due to limited display area, 100Ωand 1000ΩRTD's are indicated on
the display by a momentary readout of "RTD-100" (or "RTD-1000")
when first selected.
Thermistors are identified by a momentary alpha-numeric readout of
"Y-400" (signifying YSI Series-400 type thermistor).