99 Washington Street
Melrose, MA 02176
Fax 781-665-0780
TestEquipmentDepot.com
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.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - FAX 781.665.0780 - TestEquipmentDepot.com
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)
2 421502 Ver. 1.9 12/05
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.
3 421502 Ver. 1.9 12/05
"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).
4 421502 Ver. 1.9 12/05
Elapsed Timer
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 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.
SET Mode (for Relative Mode, HI/LO Alarm setpoints, and Clock/Timer settings)
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
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. Press 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.
Alarm HI/LO Limit Programming in SET Mode
Press the "SET" key once and then the "ENTER" key twice. 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.
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.
"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.
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).
5 421502 Ver. 1.9 12/05
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - FAX 781.665.0780 - TestEquipmentDepot.com
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