Extech Instruments 421502 User manual

User Manual

Dual Input Type J/K Digital Thermometer

Model 421502

Additional User Manual Translations available at www.extech.com

421502-en-GB_V2.0 3/19

Introduction

Thank you for selecting the Extech 421502 Digital Thermometer. The 421502 features

dual thermocouple inputs, T1, T2, and T1 –T2 displays, MIN-MAX-AVG recording,

selectable units of measure, high/low alarms, automatic power OFF, and data hold. This

professional meter, with proper care, will provide years of safe reliable service. Visit

www.extech.com for the latest version of the user manual.

Meter Description

1. Thermocouple Input Jacks (T1 and T2)

2. LCD Display. The primary temperature display is the

readout in large digits on the top row. The secondary

displays are shown on the bottom row (smaller digits)

and include a temperature reading (lower left) and the

real time clock (lower right). Temperature readings can

be set to show T1, T2, or T1 minus T2 temperatures

3. Dual-function control buttons. Primary function printed

on buttons and secondary function printed above

buttons (numerical keypad and ENTER button)

Note: The battery compartment (not pictured) is located on

back of meter. The meter’s protective jacket must be

removed to gain access to the compartment.

Operation

Meter Power

Ensure that a fresh 9V battery is installed (rear compartment) before powering the

meter. Press the power button (upper left button) to switch the meter ON or OFF. The

meter is equipped with an APO utility where it switches off automatically after 30

minutes of inactivity. If the SET or MIN-MAX-AVG mode is engaged, APO is disabled, and

the meter cannot be powered down manually. Exit these modes before attempting to

power down. Long press the “MIN-MAX”button to exit the MIN-MAX-AVG mode. To exit

the SET mode, use the “ENTER” button to step back to the normal operating mode.

Connecting Thermocouples

The thermocouples connect to the T1 and T2 input jacks on the top of the meter (observe

correct polarity). The meter accepts type J or K thermocouples, select the thermocouple

421502-en-GB_V2.0 3/19

type in the SET mode. A type-K thermocouple is supplied. Safety note: The supplied

thermocouple can only be used to measure temperature to 260oC (500oF). To measure

higher temperatures please obtain a thermocouple rated for higher temperature.

Temperature Units

Press the "oC/oF" button to toggle the temperature units. The meter recalls the selected

unit of measure when power is cycled.

Data Hold

Press the "HOLD" button to freeze the displayed reading. The "HOLD" indicator will

appear. Press "HOLD" again to return to normal operation. In MIN-MAX-AVG mode,

pressing the "HOLD" button pauses MIN-MAX-AVG recording (pressing "HOLD" again

resumes recording).

Primary and Secondary Display Modes (T1, T2, or T1 - T2)

Use the "T1 T2 / T1 - T2" button (the button with the number “4”overlay), to select the

mode for the meter's primary display (top, large digits). Press the "T1 T2 / T1 - T2" button

(the button with the minus sign [-] overlay) to select the mode for the meter's secondary

display (lower, smaller digits).

Choose "T1 or T2" to select thermocouple input 1 or 2 for display. Select "T1 - T2" to

display the difference between the two thermocouple measurements. In T1 - T2 mode, a

reading of zero indicates that both thermocouples are reading the same temperature.

Set the Thermocouple type

Choose Type-K or Type-J thermocouple using the “K/J” buttons. The “K/J” button with the

number “5” overlay applies to the primary display (large digits). The “K/J” button with the

“0” overlay applies to the secondary display (smaller digits). The selection must match

the inserted thermocouple type for accurate temperature measurements. The meter

remembers the selection when power is cycled.

Taking Temperature Measurements

The tips of thermocouple probes are used to sense temperature. Touch the tip of the

probe to an object’s surface to measure its temperature. You can also use a

thermocouple to measure the air temperature by placing the tip of the thermocouple in a

room, enclosure, or other area. Use care when placing the thermocouple; do not place it

in liquids or near live electrical circuitry.

421502-en-GB_V2.0 3/19

MIN-MAX-AVG mode (Primary Display)

1. Press the "MIN-MAX" button to access the mode and to start recording the

minimum, maximum, and average temperature readings

2. Use the “MIN-MAX” button to step through MIN, MAX, and AVG modes (the display

icons MIN, MAX, and AVG will change with each button press)

3. When a new MIN or MAX is detected, the previous MIN or MAX is replaced. An

audible beep alerts the user when a new MIN or MAX is recorded

4. Use the “HOLD” button to pause/resume recording

5. Long press the “MIN-MAX” button to exit and to reset the MIN-MAX-AVG memory

6. When recording is paused, the stored values are held in memory until MIN-MAX-

AVG mode is canceled or resumed

7. The Auto Power OFF utility is disabled, and the meter cannot be manually powered

OFF, in the MIN-MAX-AVG mode. Long press the “MIN-MAX” button to exit and

return to normal operation.

Relative (REL) Mode (Primary Display)

Relative mode allows the user to store a reference temperature for comparison with

subsequent measurements. The reference temperature can be automatically or manually

set (for manual entry, see the SET mode section). For automatic entry, the displayed

temperature is used as the reference value. Perform the steps below:

1. Press the “REL” button (the REL icon appears)

2. The currently displayed temperature becomes the reference value and

subsequent measurements represent the actual temperature minus the

reference temperature

3. Press the “REL” button to exit (the REL icon will switch OFF)

Real Time Clock and Elapsed Timer

The time display (bottom right) shows the real time clock. Refer to the SET mode section

to set the real time clock. The clock can also be used as an elapsed timer by resetting the

clock to zero. The clock allows you to see when MIN-MAX updates occur. Each time a new

MIN or MAX value is updated, the associated time is stored.

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SET Mode

Manually Setting the Relative (REL) Reference Value

Note: Refer to the Relative Mode section for setting the temperature reference value

automatically, using the currently displayed temperature as the reference value.

To set the reference manually and to then use the Relative Mode, press the "SET" button;

the display will show dashes “ - - - -“. Enter a reference temperature using the numeric

buttons. You must use leading zeros; for example, enter 0050.0 to for a 50.0oreference

temperature. Once the reference value is entered, press the “ENTER”button four times.

To display the difference between the actual temperature and a manually entered

Relative value, press the REL key and then the SET key. The meter will now display actual

temperature minus the reference temperature. Press the “REL” button to exit the mode.

Setting the Real Time Clock/Elapsed Timer

Press the "SET" button and then the "ENTER" button. Set the Hours, Minutes, and

Seconds (HH:MM:SS) using the numeric buttons. When editing is complete, the clock will

start to run. Press the "ENTER" button three times to exit. Use the “SEC/MIN”button to

switch between Hours/Minutes (Min) and Minutes/Seconds (Sec) display modes.

Setting the Alarm High/Low Limits

Press the "SET" button and then press the "ENTER" button twice. Set the desired High

Alarm limit using the numeric buttons. You must enter the value using all 5 digits,

including leading zeros. Example: 25.0oC is entered as 0025.0.

Press the "ENTER" button once. Set the Low Alarm limit using the numeric buttons. You

must enter the value using all 5 digits, including leading zeros. Example: 5.0oC is entered

as 0005.0. Press “ENTER”to exit.

To activate the high/low alarms, press the "HI/LO Limits" button, the meter will beep, and

the audio icon will appear. The meter will produce a continuous tone when a high or low

alarm limit is reached. Press the “HI/LO Limits” button to silence the alarm (see Alarm

Operation section below for more information).

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Alarm Operation

Press the "HI/LO Limits" button to enable the alarm mode (the meter will beep, and the

audio icon will appear). Set the low and high alarm limits in the SET mode. When the

actual temperature reaches the low or high alarm limit a continuous tone will be

produced. To silence the alarm (and to disable the alarm mode), press the “HI/LO Limit”

button (the audio icon will disappear).

Battery Replacement

Replace the 9V battery when the low battery icon appears on the upper left or when the

meter will not power up. To replace the battery, remove the meter’s protective jacket

and remove the two screws that secure the rear battery compartment cover. Remove the

battery, install a new battery observing correct polarity, secure the battery compartment,

and replace the meter’s protective jacket.

Battery Safety: Please dispose of batteries responsibly and never dispose of batteries in a fire,

batteries may explode or leak. When storing the meter for 60 days or more, remove the battery

and store separately.

Never dispose of used batteries or rechargeable batteries in household waste.

As consumers, users are legally required to take used batteries to appropriate collection

sites, the retail store where the batteries were purchased, or wherever batteries are

sold.

Disposal: Do not dispose of this instrument in household waste. The user is obligated to take

end-of-life devices to a designated collection point for the disposal of electrical and electronic

equipment.

Calibration and Repair Services

FLIR Systems, Inc. offers calibration and repair services for the Extech brand products we sell. We

offer NIST traceable calibration for most of our products. Contact us for information on calibration

and repair availability, refer to the contact information below. Annual calibrations should be

performed to verify meter performance and accuracy. Product specifications are subject to change

without notice. Please visit our website for the most up-to-date product information:

www.extech.com.

Contact Customer Support

Customer Support Telephone: U.S. (866) 477-3687; International +1 (603) 324-7800

Calibration, Repair, and Returns email: [email protected]

Technical Support: https://support.flir.com

www.extech.com

421502-en-GB_V2.0 3/19

Specifications

Display

5-digit multifunction LCD

Battery Power

9V (NEDA 1604, IEC 6F22, or 006P)

Auto Power OFF (APO)

Meter switches OFF after approx. 30 mins. of inactivity

Battery life

160 hours typical with carbon zinc battery

Dimensions / Weight

192 x 91 x 52.5mm (7.5 x 3.6 x 2.1”) / 365g (11.7 oz.)

Type-J thermocouple range

-200 ~ 1050oC (-328 ~ 1922oF)*

Type-K thermocouple range

-200 ~ 1370oC (-328 ~ 2498oF)*

*Safety note: The supplied type-K thermocouple can only be used

to measure temperature to 260oC (500oF). To measure higher

temperatures please obtain a thermocouple rated for higher

temperature

Resolution

0.1oC (0.2oF)

Temperature units

Selectable oC / oF

Accuracy

± (0.05% rdg + 0.3oC) -50oC ~ 1370oC

± (0.05% rdg + 0.7oC) -50oC ~ -200oC

± (0.05% rdg + 0.6oF) -58oF ~ 2498oF

± (0.05% rdg + 1.4oF) -58oF ~ -328oF

Temperature Coefficient

0.1 times the applicable accuracy specifications per oC from 0oC ~

18oC and 28oC ~ 50oC (32oF ~ 64oF and 82oF ~ 122oF)

Water resistant housing

Gasket protected front panel

Input Protection

24VDC or 24VAC rms max. input on any combination of inputs

Measurement rate

One reading per second

Input connectors

Accepts standard miniature thermocouple connectors

Supplied thermocouple

Type-K with Teflon® insulation. Cable length: 4 ft. (1.2m)

Max. insulation temperature: 260oC (500oF)*

Accuracy: ± 2.2oC (4oF) or ± 0.75% of reading (whichever is greater)

*Safety note: The supplied thermocouple can only be used to

measure temperature to 260oC (500oF). To measure higher

temperatures please obtain a thermocouple rated for higher

temperature.

Operating conditions

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

Storage conditions

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

Alarm beeper volume

95dB

Table of contents

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