Extech 421502 Instruction Manual

INSTRUCTION MANUAL

Model 421502

Dual Input Type J/K Digital Thermometer

• Dual input T1 / T2 / T1 – T2 displays

• Maximum temperature record mode

• Selectable units

• Data Hold

1. INTRODUCTION

Congratulations on your purchase of Extech’s Digital Thermometer. This professional meter,
with proper care, will provide years of safe reliable service.

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2. SPECIFICATIONS

Display 5 digit LCD multifunction display
Battery Power Supply NEDA 1604, IEC 6F22, or 006P 9VDC battery.
Auto Power off Meter shuts down after approx. 30 mins. of inactivity
Battery life 100 hours typical with carbon zinc battery
Dimensions / Weight 7.5 x 3.6 x 2.1” (192x91x52.5mm); 11.7oz. (365g)
J TC Range -328 to 1922oF (-200 to 1050oC)
K TC Range -328 to 2498oF (-200 to 1370oC)
Resolution 0.1oC or 0.2oF
Temperature units Selectable C or F temperature units
Accuracy

±(0.05% rdg + 0.3oC) -50oC to 1370oC
±(0.05% rdg + 0.7oC) -50oC to -200oC
±(0.05% rdg + 0.6oF) -58oF to 2498oF
±(0.05% rdg + 1.4oF) -58oF to -328oF

Temperature Coefficient 0.1 times the applicable accuracy specifications per oC

from 0oC to 18oC and 28oC to 50oC (32oF to 64oF and 82oF
to 122oF)

Water resistant housing Gasket protected front panel
Input Protection 24VDC or 24VAC rms max. input on any combination of

inputs. Max voltage between T1 and T2 inputs = 1V
Reading rate One reading per second
Input connectors Accepts standard miniature thermocouple connectors
Supplied thermocouple 4', type K, teflon insulation,

Max insulation temp: 260oC (500oF)

Accuracy: +2.2oC or +0.75% of rdg

(whichever is greater) from 0oC to 800oC
Ambient Operating
Range
Storage Temperature

32 to 122oF (0 to 50oC); less than 80% RH

-4 to 140oF (-20 to 60oC); less than 70% RH

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3. FRONT PANEL DESCRIPTION

FIGURE 1

Note: The 12 keys on the meter keypad double as numeric keys (0-9), minus key, and

ENTER key. The Display icons and key functions are explained in the meter operation
instructions below.

4. OPERATION

4.1 Ensure that a fresh battery is installed by powering the meter (press the Power key)
and observing the LCD display. If the LCD does not display characters, check the battery.

4.2 Connect the thermocouples to the meter’s thermocouple input jacks (meter top).

NOTE: If the SET, RELATIVE, or MIN/MAX/AVG MODE is engaged, the meter cannot be
powered down. Exit these modes before attempting to power down.

4.3 Temperature Units: The meter's dual display (one for each thermocouple input) can
read either in oC or oF. Press the "C/F" key to toggle between oC and oF temperature units.
The meter recalls the selected units of measure the next time the meter is powered up.

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4.4 Data Hold Mode: During measurements, pressing the "Hold" key "freezes" the MAIN
DISPLAY temperature value and the "HOLD" indicator will appear on the LCD. Press
"Hold" again to return to normal operation. In MIN/MAX Mode, pressing the "Hold" key
cancels the data recording session (pressing "Hold" again resumes recording).

4.5 Main Display Input Selection "T1, T2, or T1 - T2"
Pressing the "T1 T2 / T1 - T2" key (the key with the number 4 overlay) permits the user to
select the thermocouple input configuration which will be reflected on the meter's Main
Display (largest LCD digits). Choose "T1 or T2" to show either thermocouple input 1 or 2
respectively. Select "T1 - T2" to display the difference between the two thermocouple
input temperatures. In T1 - T2 mode, a reading of zero indicates that both thermocouples
are reading the same temperature.

4.6 "K/J" Key (Selecting theThermocouple Type for the T1 Main Display)
For the type of thermocouple that is plugged into the T1 terminal on the meter, select K or
J to match it by toggling the "K/J" key. The meter remembers this selection upon power
OFF.

4.7 MIN/MAX/AVG Temperature mode (for Main Display only)
To enter this mode, press the "MIN/MAX" key. Repeated key-presses cycle through Min,
Max, and Avg modes each with its own LCD icon. Once this key is pressed, the meter
begins recording peak, valley, and average temperatures. Each time a new peak is
measured, the previous Max displayed value is replaced. The same applies to the Min
function. An audible beep alerts the user that a new peak or valley has been recorded. To
toggle between start/stop recording, press the HOLD key. When recording is stopped, the
stored values are held in meter memory until Min/Max/Avg mode is canceled or resumed
by pressing the "Hold" again.

The Avg mode keeps a true running average of temperatures recorded since the
"MIN/MAX" key was first pressed (up to a maximum of 22 hours). If 22 hours elapse the
average stored at this point is held on the display and is no longer updated (the MIN and
MAX functions continue without interruption indefinitely). If an overload is recorded, the
Avg function is halted and the Avg. display shows "-------".

NOTE: Keep in mind that the main displayed value is either the Min, Max, or Avg reading
depending upon which icon appears on the LCD. Cycle through Min/Max/Avg with the
"MIN/MAX" key.

The Min/Max/Avg mode cancels the Auto Power OFF feature, disables most of the meter
keys, and will not allow a manual power OFF.

Note: Press and hold the MIN/MAX key for several seconds to return to normal operation.

4.8 Relative Mode (REL) for Main Display Only
The Relative Mode permits the user to store the current temperature value (or enter one
manually - see Set Mode) and compare it to subsequent temperature readings. The
display then shows: Actual temp. minus the Relative temp. = Displayed temperature). To
enter this mode press the "REL" key and the REL icon will appear on the LCD. While in
REL Mode the Main Display will show the difference between actual temperature and the
relative temperature previously entered. Press the REL key again to exit the REL Mode.
To display the difference between the actual temperature and a manually entered Relative
value, press the REL key and then the SET key (see SET mode below).

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4.9 Real-Time/Elapsed Timer Clock
The Timer (third display on bottom right of LCD) displays Clock or Elapsed Time and is a
convenient way to see when Min and Max temperatures occurred. Each time new Min or
Max temperature values are stored, the timer/clock value for the that Max or Min
temperature is also stored for later recall. Real time can be entered by setting the meter's
clock to the current time (set Hours:Mins display using the MIN/SEC key). To use the
clock as an elapsed timer, first reset the clock to zero in Set Mode (see next section). The
timer will begin counting as soon as it is set in SET mode.

4.10 SET Mode (for Relative Mode, HI/LO Alarm setpoints, and Clock/Timer settings)

4.10.1 Manually setting the Relative Values in SET Mode
Press the "SET" key once and the display will go to all dashes "======". Enter the
relative value using the meter's keys which double as numeric keys. USE LEADING
ZEROS SINCE DISPLAY IS 5-DIGITS. Once the Relative value is entered, press the
ENTER key FOUR times to return to normal operation. Meter will now display Actual
Temperature minus Relative Temperature

4.10.2 Setting the Timer/Clock in SET Mode
Press the "SET" key and then the "ENTER" key. Next key in the Hours, Minutes, and
Seconds (HH:MM:SS) via the overlay numeric keys. When editing is complete, the clock
will begin counting. Pr ess the "ENTER" key three times to return to normal meter
operation. Now use the SEC/MIN key to toggle between Hours/Minutes and
Minutes/Seconds display.

4.10.3 Alarm HI/LO Limit Programming in SET Mode
Press the "SET" key once and then the "ENTER" key tw ice. Key in the desired HI Alarm
value (high temperature at which the meter will audibly alert the user) via the overlay
numeric keys. Now press the "ENTER" key once. Next, key in the LO Alarm Limit value
(low temperature at which the meter audibly alerts the user). Press the ENTER key once
to return to normal operation. After exiting the SET mode, press the "HI/LO Limits" key
to activate the Alarm, the audio icon on the LCD tells you that the Alarm is now armed
and will alert you if HI/LO limits are encountered.

4.11 Second Display Input Selection "T1, T2 or T1-T2"
Pressing the "T1 T2 / T1 - T2" key (the key with the minus sign printed over it) permits the
user to select the thermocouple input configuration which will be reflected on the meter's
Second Display (lower left LCD). Choose "T1 or T2" to show either thermocouple input 1
or 2 respectively. Select "T1 - T2" to display the difference between the two
thermocouple input temperatures. In T1 - T2 mode, a reading of zero indicates that both
thermocouples are reading the same temperature.

4.12 "K/J" Key (Selecting theThermocouple Type for the T2 Main Display)
For the type of thermocouple that is plugged into the T2 terminal on the meter, select K or
J (to match input) by toggling the "K/J" key. The meter remembers this selection upon
power OFF.

4.13 HI/LO Alarm Limits Mode
Press the "HI/LO Limits" key to arm the HI/LO Alarms (the audio speaker icon will appear
on the right side of the LCD). When the actual temperature meets or exceeds the user
programmed temperature limits a continuous alert tone will be heard. To disarm or silence
a tripped Alarm press the HI/LO Limit key again (the audio display icon will disappear).

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5. BATTERY REPLACEMENT

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Replace the battery when the low battery indication symbol appears on the upper left
corner of the display. To replace the battery, remove the two screws that secure the rear
battery compartment cover. Remove the old battery, install a new one, and replace cover

6. CALIBRATION / REPAIR SERVICES

Extech offers complete repair and calibration services for all of the products we sell. For
periodic calibration, NIST certification or repair of any Extech product, call customer
service for details on services available. Extech recommends that calibration be performed
on an annual basis to insure calibration integrity.

7. WARRANTY

EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and
workmanship for one year from date of shipment (a six month limited warranty applies on sensors and
cables). If it should become necessary to return the instrument for service during or beyond the warranty
period, contact the Customer Service Department at [phone] ext. 210 for authorization. A Return
Authorization (RA) number must be issued before any product is returned to Extech. The sender is
responsible for shipping charges, freight, insurance and proper packaging to prevent damage in transit.
This warranty does not apply to defects resulting from action of the user such as misuse, improper wiring,
operation outside of specification, improper maintenance or repair, or unauthorized modification. Extech
specifically disclaims any implied warranties or merchantability or fitness for a specific purpose and will not
be liable for any direct, indirect, incidental or consequential damages. Extech's total liability is limited to
repair or replacement of the product.
The warranty set forth above is inclusive and no other warranty, whether written or oral, is expressed or
implied.

Copyright © 1999 Extech Instruments Corporation. All rights reserved

including the right of reproduction in whole or in part in any form.

Tech Support Hotlines

781-890-7440 ext. 200

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