Extech 421502 Operating Manual

User’s Guide

Model 421502
Dual Input Type J/K
Digital Thermometer

• Dual input T1 / T2 / T1 – T2 displays

• Maximum temperature record mode

• Selectable units

• Data Hold

INTRODUCTION

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

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 160 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

Temperature Coefficient 0.1 times the applicable accuracy specifications per oC from 0oC

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

Reading rate One reading per second
Input connectors Accepts standard miniature thermocouple connectors
Supplied thermocouple 4', type K, teflon insulation,

Ambient Operating Range
Storage Temperature
Alarm 95dB

±(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

o

C and 28oC to 50oC (32oF to 64oF and 82oF to 122oF)

to 18

Max voltage between T1 and T2 inputs = 1V

Max insulation temp: 260oC (500oF)
Accuracy: +

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

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

2.2oC or +0.75% of rdg (whichever is greater)

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FRONT PANEL DESCRIPTION

1. Thermocouple Input Jacks

2. LCD Display

1

2

3. Keypad

3

OPERATION

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.

Connect the thermocouples to the meter’s thermocouple input jacks (meter top).
NOTE: If the SET or MIN/MAX/AVG MODE is engaged, the meter cannot be powered

down. Exit these modes before attempting to power down.
Temperature Units

The meter's dual display (one for each thermocouple input) can read either in
Press the "C/F" key to toggle between

o

C and oF temperature units. The meter recalls the

selected units of measure the next time the meter is powered up.

o

C or oF.

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).

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.

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"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.

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.

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.

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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