General Tools IRT730K User Manual

30:1 ULTRA WIDE-RANGE

IR THERMOMETER

WITH “K” PORT

USER’S MANUAL

IRT730K

Please read this manual carefully and thoroughly before using this product.

TABLE OF CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Key Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

What’s in the Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 –5

Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Install Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 – 10

Using the IRT to Measure Temperature . . . . . . . . . . . . . . . . . . . 6 –7

Choosing an IRT Display Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 7 –8

Adjusting Emissivity and Setting Temperature Alarms . . . . . . . . 8 –9

Recalling Stored Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 – 10

Using the “K” Type Probe to Measure Temperature . . . . . . . . . . . . 10

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Operating & Maintenance Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 – 12

Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Return for Repair Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Appendix I. How to Make Accurate IR Temperature Measurements . . 13 – 14

Appendix II. Emissivities of Common Materials . . . . . . . . . . . . . . . . . . . . . . 15

INTRODUCTION

Thank you for purchasing General Tools & Instruments’ (General’s) IRT730K 30:1 Ultra Wide­Range IR Thermometer with “K” Port. Please read this manual carefully and thoroughly before
using the thermometer.

The IRT730K measures surface temperature using either of two methods: non-contact (using
an IR thermometer with a laser pointer) or contact (using a “K” type thermocouple). A “K” type
bead thermocouple with a measurement range of -40° to 500°F (-40° to 260°C) is included in
the package. Non-contact measurements made by the IRT can be adjusted for the emissivity
of the surface, increasing the accuracy of readings.

The instrument automatically stores (records) up to 100 temperature readings in nonvolatile
memory for later recall. During a single scanning session, the IRT730K simultaneously displays
real-time measurements on a primary (larger) readout and the maximum, minimum or average
measurement, or the largest difference between measurements, during that session on a
secondary (smaller) readout.

The IRT730K, the “K” type bead thermocouple, a “9V” battery and this user’s manual are
packaged in a soft pouch inside a box.

2

KEY FEATURES

• Extremely wide measurement range

• Adjustable emissivity

• Laser targeting ring outlines analysis area

• Port for included “K” type bead thermocouple probe or another “K” type probe

• Releasing trigger holds measurement

• Automatically stores last 100 readings for recall

• Min/Max/Avg/Dif displays

• Adjustable Hi and Lo temperature alarm setpoints

• Large backlit LCD w/dual 4-digit readouts

• Auto power off

• °C/°F and laser on/off buttons

• Low battery indicator

• 3-year limited warranty

SAFETY INSTRUCTIONS

CAUTION!

The IRT730K is a Class 2 laser product that emits less than 1mW of radiation at a wavelength
between 630 and 670nm. Avoid looking directly at the laser pointer. U.S. law prohibits pointing a
laser beam at aircraft; doing so is punishable by a fine of up to $10,000 and imprisonment.

The laser may cause discomfort if viewed directly. Your eyes’ natural aversion reflex will
prevent you from looking at the beam long enough to cause harm. As a precaution, keep the
IRT730K out of the hands of children, especially if you have pets.

Never stare at the laser beam through binoculars or a magnifying glass.
Do not operate the IRT in the presence of flammable or explosive gases or in environments full

of dust or static electricity.
Do not operate the unit near a source of a strong electromagnetic field, such as an arc welder

or an induction heater.
Be careful not to burn yourself when attaching the bead thermocouple probe to a hot surface.

3

WHAT’S IN THE PACKAGE

The IRT730K comes in a soft pouch inside a box along with a “K” type bead thermocouple
probe, a “9V” battery and this user’s manual.

PRODUCT OVERVIEW

Fig. 1 shows all controls, indicators, connectors and other physical features of the IRT730K.
Fig. 2 shows all possible indications on the unit’s LCD. Familiarize yourself with the positions of
all controls and connectors and the meaning of all display indications and icons before moving
on to the Setup Instructions and Operating Instructions.

10

1

1. Laser pointer

2. Infrared sensor

3. Measurement trigger

4. Battery compartment

5. Jack for spade-type
thermocouple probe

6.

MODE

button

7. / (laser/backlight) button

8.

°C/°F

button

9. LCD

10. Laser identification/certification/
warning/safety labels
(on left side of unit);
see below

9

8
7
6

Fig. 1. All controls, indicators, connectors
and other physical features of the IRT730K

2

3

4

5

4

1. Scanning indication (flashes)

2. Emissivity setting

3. Laser pointer on

4. Backlight on

5. Operating in continuous
measurement mode (not used)

6. Selected temperature unit

7. Difference value on secondary readout

8. Average value on secondary readout

9. Minimum value on secondary readout

10. Secondary readout

11. Low battery icon

12. Low alarm setpoint

13. Low alarm activated

14. High alarm activated

15. High alarm setpoint

16. “K” type probe reading on
secondary readout

17. Minimum value on secondary readout

18. Automatically storing readings

19. Primary readout

20. Held reading on primary readout

Fig. 2. All possible display indications

SETUP INSTRUCTIONS

INSTALL BATTERY

The IRT730K’s battery compartment (Fig. 1, Callout 4) is below the measurement trigger and
accessible from the front of the grip. Before installing the “9V” battery included in the
package, remove the plastic wrap covering its terminals.

To install the battery:

1. Open the battery compartment by placing your thumb and forefinger in the indentations
on the sides of the grip and pulling the top of the hinged compartment forward.

2. Plug the “9V” battery into the wired socket inside the compartment. The terminals of the
battery and the socket mate in only one way, with the smaller male terminal plugging into
the larger female terminal.

3. Close the battery compartment cover by pushing its top against the grip until the cover
snaps shut.

5

OPERATING INSTRUCTIONS

USING THE IRT TO MEASURE TEMPERATURE

This section describes how to operate the IRT730K in its “normal” mode, with and without use

REC

of the backlight and/or laser pointer. In this mode (called
by squeezing the measurement trigger is automatically stored (recorded) in a numerically
tagged location in the instrument’s nonvolatile memory. After 100 measurements are stored,
the 101st measurement made overwrites (erases) the first one. The section also explains how
to change the factory default temperature unit from °F to °C.

1. Carefully remove the protective plastic film covering the LCD.

Power on the IRT730K

2.
(Fig. 1, Callout 3) while pointing the unit anywhere. The LCD and its gray backlight will
illuminate and the laser pointer will activate. (If none of these three things happen, the
IRT’s battery is dead and must be replaced; see p. 5 for instructions.) Note that squeezing
the trigger causes the word
corner of the LCD.

3.

Release the trigger.

I. The unit will “chirp.”
II. The word
III. The measured temperature will appear on the primary (large) readout in °F, with the

text
automatically stored (recorded) in the IRT730K’s nonvolatile memory.

IV. The measured temperature will also appear on the secondary (smaller) readout,

following the brief appearance of a two-digit number. If this is the IRT’s first
measurement, that number will be
memory storage location.

4. S

queeze and hold the trigger again

release the trigger. As before, the unit will chirp and
temperature of the second target will again appear on both the primary and secondary
readouts. This time, however, note that the second reading will be accompanied by the
brief appearance of the memory tag

5.

Squeeze and hold the trigger again

will occur, with the new reading tagged
30 seconds, the IRT’s Auto Power Off (APO) function will activate and cause the unit to
shut down silently.

To change the measurement unit from the factory default °F to °C

(Fig. 1, Callout 6) once briefly while operating in
middle of the LCD. Then press the
Fahrenheit readings on both readouts to the corresponding Celsius values.

To return to operation in

REC

will replace

the IRT730K’s six display modes other than

SCAN

REC

at its lower left.

MAX

by squeezing and holding the yellow measurement trigger

SCAN

(Fig. 2, Callout 1) to appear, flashing, in the upper left

The following events will occur in a rapid-fire sequence:

will disappear and be replaced by the word

REC

indicates that the measurement is about to be

01

. The number represents the measurement’s

while pointing the IRT at a different target. Then

02

on the secondary readout.

and then release it. The same sequence of events

03

in memory. Allow 30 seconds to pass. After

REC

mode.

°C/°F

button (Fig. 1, Callout 8). This will convert the

REC

mode, press the

. The next section of the manual explains how to switch to operation in

REC

MODE

button seven times with

and

MAX

mode), each measurement made

HOLD

just below it.

SCAN

will be replaced by

, press the

REC

will be replaced by

.

MODE

MAX

HOLD

MAX

on-screen.

. The

button

in the

6

To turn off the laser pointer

, press the / button (Fig. 1, Callout 7) while squeezing and
holding the measurement trigger. The icon (Fig. 1, Callout 3) will disappear from the top
row of the LCD. To re-enable the laser pointer, press the / button while squeezing and
holding the measurement trigger.

To disable the LCD backlight

operating in scanning mode (i.e., the trigger has been released to replace

, press the / button while the unit is powered on but

SCAN

by

HOLD

not

).

The icon will disappear from the top line of the LCD. To re-enable the backlight, press the

/ button again while the unit is powered on and

operating in

SCAN

mode.

not

CHOOSING AN IRT DISPLAY MODE

Because the IRT730K automatically records and tags every measurement it makes, it can
analyze the set of readings made and stored over any finite period of time. Often, the period
that provides the most useful information is the measurement session—the time during which
you measure the temperature of multiple objects or surfaces. The session begins when you
squeeze the trigger to “wake up” the IRT; it typically ends 30 seconds after you have finished
making measurements with the activation of the APO function.

What the IRT730K can do is display the maximum and minimum temperatures recorded during
a measurement session. It can even calculate and display the average reading and the
difference between the highest and lowest readings. The value of being able to quickly
determine the hottest or coldest object of a group, or the difference between their
temperatures, should be obvious.

These four display modes—

MODE

pressing the

button the correct number of times. The currently selected display mode is

MAX, MIN, AVG

and

DIF

—can be entered from

REC

mode by

indicated by its three-letter abbreviation in the middle of the display. The value of that
parameter—the session’s maximum, minimum or average temperature, or the difference
between the hottest and coldest temperature—is shown on the secondary readout.

The IRT730K also can display three other parameters:

• The temperature of an object or surface touched by the included “K” type bead
thermocouple probe or any other “K” type probe. This temperature is identified by the
two-letter abbreviation

• The high and low temperature alarm setpoints

TK

. See p. 10 to learn how to use the external temperature probe.

HAL

and

LAL

. Each can be set to any
integral value from -58° to 1472°F (-50° to 800°C)—the measurement range of the
IRT730K. The factory preset value for
that the unit can measure. The factory value for

HAL

is 1472°F (800°C)—the highest temperature

LAL

is -58°F (50°C)—the lowest

temperature that the unit can measure.

By default, when the unit powers on in response to your squeezing the trigger, the unit
resumes operation in the same display mode it was in when the APO function powered the

MODE

IRT off. To change the display mode, you use the
sequence comprising the five display modes (
two alarm setpoints

HAL

and

LAL

, as shown in the figure on the next page.

REC, MAX, MIN, AVG

button to cycle through an eight-step

and

DIF

) plus TKand the

7

To move from one display mode to the
next in the sequence, briefly press

MODE

(but do not hold) the

button.

ADJUSTING EMISSIVITY AND SETTING TEMPERATURE ALARMS

The IRT730K has three parameters that you can set anywhere over a predefined range:

1.

Emissivity (ε)

—the ability of an object to reflect or absorb IR radiation (energy)—can be
assigned any value between 0.10 and 1.00 in steps of 0.01. The default (factory setting)
of ε is 0.95. Because the IRT730K measures the amount of infrared energy emitted by a
surface, its measurements are most accurate when they take into account the
characteristic emissivity of the target material.

A perfectly absorbent surface (called a black body) has an emissivity of 1; it absorbs
100% of the thermal energy hitting it. An object with an emissivity of 0.8 absorbs 80% of
IR energy and reflects 20% of it. All emissivity values fall between 0 and 1; as a rule, the
shinier the surface, the lower its emissivity.

To maximize the accuracy of IRT730K measurements, you should enter the actual
emissivity of the target surface (see Appendix II) using the instrument’s three buttons and
the procedure below. Compensating for emissivity will particularly improve the accuracy
of measurements of surfaces with emissivities nearer to zero than to the
default IRT730K setting of 0.95.

2.

High Temperature Alarm (HAL)

. As mentioned earlier, the

HAL

setpoint can be set to any
integral temperature value from -58° to 1472°F (-50° to 800°C)—the operating range of
the IRT730K.

3.

Low Temperature Alarm (LAL)

. The

LAL

setpoint also can be set to any integral
temperature value from -58° to 1472°F (-50° to 800°C)—the operating range of the
instrument.

The presetting of the high and low temperature alarms to the high and low limits of the
instrument’s measurement range is a convenience. If you never change the value of

LAL

(because you choose not to use temperature alarms) from its default value, you will never

HAL

be bothered by an alarm inadvertently sounding because you forgot to reset an alarm
threshold. Neither alarm can be disarmed.

or

8

The High Temperature Alarm is activated when the temperature measured by the IRT is higher

HAL

than the
measured by the IRT is lower than the

setpoint. The Low Temperature Alarm is activated when the temperature

LAL

setpoint. In each case, the IRT730K responds by
sounding a second chirp (following the usual first chirp to indicate that a measurement was
made and stored) and flashing an icon on the bottom line of the LCD (Fig. 2, Callouts 13 and

14). The second chirp is the only audible indication that a temperature alarm has been
activated.

To change the unit’s emissivity setting and either alarm threshold, press and hold the MODE

with the instrument powered on and operating in any mode.

button

Whatever the operating mode, pressing and holding the

MODE

button will cause the emissivity
icon ε (Fig. 2, Callout 2) on the top line of the LCD to begin flashing. You now have 30 seconds
to change the emissivity value before the APO function activates. You can change ε in 0.01

°C/°F

steps by pressing either the

button to decrease the value or the / button to

increase the value. To move up or down quickly, press and hold either button.

MODE

With ε flashing, pressing the
or not you have adjusted it) and changes the adjustment target to
button causes

HAL

to begin flashing on the bottom left of the LCD. Once

button briefly saves the currently displayed value (whether

HAL

. Pressing the

HAL

MODE

begins flashing,

you have 30 seconds to adjust its value up or down to any temperature within the unit’s

°C/°F

measurement range. Press the

button to decrease the value or the / button to

increase it. To move up or down quickly, press and hold the corresponding button.

MODE

Pressing the

button briefly with
changes the adjustment target to
on the bottom right of the LCD. Once

HAL

LAL

. Pressing the

LAL

begins to flash, you have 30 seconds to adjust its

flashing saves the currently displayed value and

MODE

button causes

LAL

to begin flashing

value up or down to any temperature within the unit’s measurement range. As before, press
the

°C/°F

button to decrease the value or the / button to increase it. To move up or down

quickly, press and hold the corresponding button.
Pressing the

button with

LAL

flashing returns the three-step sequence to its starting

MODE

point—with ε flashing on the top line. The figure below shows the sequence in graphic form.

Be aware that, unlike values shown on the
primary and secondary readouts (all of which
have 0.1° resolution),

LAL

and

HAL

only have
1° resolution. In other words, do not mistake
the default value of

HAL

(1472°F) for 147.2°F.

RECALLING STORED READINGS

To recall the measurements made and automatically saved by the IRT730K during operation in

REC

mode:

1. Power on the unit by squeezing the measurement trigger.

2. Release the trigger to exit

SCAN

mode. Doing so automatically stores the current IRT
measurement in memory. For the purpose of illustrating how stored measurements are
numerically tagged, assume that this reading is given the memory tag

83

.

9

3. Press the

MODE

button as many times as necessary to enter

REC

mode. At this point, the

values on the primary and secondary displays will be identical.

82

83

.

4. To recall the value stored just prior to the measurement that was just stored (with tag

°C/°F

press the

button once. The number 82will appear briefly (for less than a second) on

the secondary display, followed by the value of the measurement stored with tag

°C/°F

5. Press the
of the measurement stored with tag

As you can see, by pressing the

button again and 82will be briefly replaced by 81, followed by the value

81

.

°C/°F

button repeatedly you can recall all stored IRT
measurements in reverse chronological order (newest through oldest). By pressing the /
button, you can recall stored IRT measurements in chronological order (oldest through
newest). However, unless you have kept track of which tags have been assigned to particular
measurements, you typically will recall readings stored long ago. For example, pressing the

°C/°F

/ button instead of the

temperature associated with it. That value, and the values associated with tags

button in Step 4 above would recall tag 84, followed by the

85

and 86,
would likely be irrelevant because they represent measurements made nearly 100 hundred
trigger squeezes ago.

USING THE “K” TYPE PROBE TO MEASURE TEMPERATURE

To measure the temperature of a surface using the included “K” type thermocouple probe
(or another “K” type probe):

1) Plug the two prongs of the probe into the two slots on the bottom of the IRT730K. Be sure
to insert the slightly narrower (+) prong into the slightly narrower slot, which is closer to
the rear of the unit.

MODE

2) Press the

button as many times as necessary to make TKappear to the left of the

secondary display.

3) Attach the end of the probe to the surface whose temperature you wish to measure.

4) Squeeze and release the measurement trigger. The temperature measured by the
thermocouple probe will appear on the secondary readout.

Unlike measurements made by the IRT, measurements made by the “K” type probe are not
stored in memory. And although the temperature measured by the IRT will simultaneously
appear on the primary readout after you release the measurement trigger, it will not be stored
in memory—because the IRT730K is not operating in

If you allow the IRT730K’s APO function to activate with the unit operating in
you power the unit back on it will resume operation in

REC

TK

mode.

mode.

TK

mode, when

),

10

SPECIFICATIONS

IRT Distance to Spot (D:S) Ratio 30:1

IRT Measurement Range -58° to 1472°F (-50° to 800°C)

IRT Measurement Accuracy ±7.2°F (4°C) from -58° to 32°F (-50° to 0°C); ±1.5% of reading or ±3.6°F

(2°C), whichever is greater, from 32° to 752°F (0° to 400°C); ±2% of
reading or ±3.6°F (2°C), whichever is greater, from 752° to 1472°F
(400° to 800°C)

IRT Measurement Resolution 0.1° (F or C) below 1000°; 1° above 1000°

IRT Emissivity Adjustable from 0.1 to 1.0 in 0.01 steps with default of 0.95

“K” Port Measurement Range: -40° to 2372°F (-40° to 1300°C)

Range of Included Probe -40° to 500°F (-40° to 260°C)

Accuracy of Included Probe ±(2% + 2 digits)

Response Time <500ms

Laser Power <1mW (Class 2) @ wavelength of 630 to 670nm

Spectral Response 8 to 14 um

Operating Temperature 32° to 122°F (0° to 50°C) @10 to 90%RH

Auto Power Off Trigger 30 seconds of front-panel inactivity

Dimensions 7.6 x 3.8 x 3.3 in. (192 x 95 x 83mm)

Weight 9.7 oz. (275g)

Power Source 1 “9V” battery (included)

OPERATING & MAINTENANCE TIPS

All IR thermometers, including the IRT730K, take the average temperature of all objects within
a circular target area. Depending on the distance to the target, the target area may include
both the target and background objects in the thermometer’s field of view. If background
objects in the field of view are cooler than the target, the measured temperature will be lower
than the target’s actual temperature. If background objects are hotter than the target, the
measured temperature will be higher than the target’s actual temperature. The IRT730K’s large
D:S ratio of 30:1 enables narrow measurement of high-temperature objects (up to
1472ºF/800ºC) from a safe distance.

To eliminate measurement error, move the IRT730K close enough to the target

created by the targeting laser falls just within the object being measured. See Appendix II for a
brief tutorial: How to Make Accurate IR Temperature Measurements.

When the Low Battery icon appears at the lower right of the LCD (Fig. 2, Callout 11), it’s time
to change the “9V” battery that powers the IRT (although measurements will remain valid for
several hours after the icon first appears). To change the battery, follow the instructions on
p. 5.

so the circle

11

If the temperature of the IRT’s target is higher than 1472°F (800°C)—the upper limit of the
unit’s measurement range—or lower than -58°F (-50°C)—the lower limit of the measurement
range—“OL” will appear on the main readout.

The IRT730K cannot make accurate measurements if there is glass or plastic between it and
the target.

Clean the lens of the infrared sensor lens (Fig. 1, Callout 2) often—but never use a solvent.
Abrupt temperature changes will cause condensation and possible vapor penetration. Clean

the LCD after the vapor evaporates. Blow off loose particles with clean, compressed air. Gently
brush remaining debris away with a lens hair brush.

To clean the housing, use a moist cotton swab or wet sponge. Avoid excessive amounts of
water and corrosive gas or liquids.

Remove the battery if you do not expect to use the IRT for an extended period of time (months
or years).

Do not drop or disassemble the unit or immerse it in water.

WARRANTY INFORMATION

General Tools & Instruments’ (General’s) IRT730K 30:1 Ultra Wide-Range IR Thermometer with
“K” Port is warranted to the original purchaser to be free from defects in material and
workmanship for a period of three years. Subject to certain restrictions, General will repair or
replace this instrument if, after examination, the company determines it to be defective in
material or workmanship. The warranty period begins on the date of purchase. You are
encouraged to register your product online. General will extend your warranty an additional
60 days if you register at www.generaltools.com/ProductRegistry.

This warranty does not apply to damages that General determines to be from an attempted
repair by non-authorized personnel or misuse, alterations, normal wear and tear, or accidental
damage. The defective unit must be returned to General Tools & Instruments or to a General­authorized service center, freight prepaid and insured.

Acceptance of the exclusive repair and replacement remedies described herein is a condition
of the contract for purchase of this product. In no event shall General be liable for any
incidental, special, consequential or punitive damages, or for any cost, attorneys’ fees,
expenses, or losses alleged to be a consequence of damage due to failure of, or defect in any
product including, but not limited to, any claims for loss of profits.

Register now at www.generaltools.com/ProductRegistry to receive a 60-day extension to your
warranty.

12

RETURN FOR REPAIR POLICY

Every effort has been made to provide you with a reliable product of superior quality. However,
in the event your instrument requires repair, please contact our Customer Service to obtain an
RGA (Return Goods Authorization) number before forwarding the unit via prepaid freight to the
attention of our Service Center at this address:

General Tools & Instruments
80 White Street
New York, NY 10013

212-431-6100
Remember to include a copy of your proof of purchase, your return address, and your phone
number and/or e-mail address.

APPENDIX I

25@750

1@30

D:S=30:1

50@1500

2@60

D

75@2250

3@90

mm

S

inches

The IRT730K’s field of view

HOW TO MAKE ACCURATE IR MEASUREMENTS

The IRT730K has a distance-to-spot (D:S) ratio of 30:1. This means that the target area
(spot) whose infrared radiation (temperature) is being measured increases in diameter
by 1 inch for every 30 inches you move away from the target. Conversely, the diameter
of the target area measured decreases by 1 inch for every 30 inches you move closer
to the target.

All IR thermometers (IRTs), including the IRT730K, take the average temperature of all
objects within a circular target area (spot). Although the distance “D” in the D:S ratio is
defined as a linear value and the “S” defines the diameter of the spot (see above figure),
the critical parameter is the target area. Depending on the distance to the target (the
object whose temperature you want to measure), the target area may include both the
target and background objects near or behind the thermometer’s field of view, which
defines the target area or spot.

13

To explain the relationship between D:S ratio and measurement accuracy, consider how
the IRT730K would be used to measure the temperature of a small AC motor suspected
of overheating. The motor measures approximately 1 ft x 1 ft, so it has an area of 1 ft

2

If the IRT730K is used to make the measurement from 60 ft. away, the reading will

2

have a large error. At this distance, the target area is 2 ft

. Therefore, the IRT730K will
measure not just the temperature of the motor, but also the temperature of the physical
surroundings in its field of view, and average the two readings.

How inaccurate would the measurement be? If the motor’s operating temperature is
200°F and the background temperature is 75°F, and the motor’s area is half the target
area at the measurement distance, the following equation gives the average
temperature of the target area:

Tavg = (Tmotor + Tbackground) ÷ 2

Solving for Tavg, we get (200 + 75) ÷ 2 or 137.5°F., which is what the IRT730K would
display. In other words, trying to measure the temperature of the motor from 60 ft.
away introduced an error of (200-137.5) ÷ 200, or 31% into the measurement. In this
case, the measured temperature was 31% below the motor’s actual temperature
because the background is cooler than the motor.

To eliminate measurement error, the IRT must be moved close enough so the motor is
the only object in the target area (see figure below). For a motor with an area of 1 ft

2

and using an IRT with a D:S ratio of 30:1, the optimum measurement distance would
be 30 ft.

For best results, the targeted area (spot) should fall within the target’s boundaries, as in
the figure below.

.

wall

Measuring a motor’s temperature from the wrong (top) and right (bottom) distance

14

APPENDIX II

EMISSIVITIES OF COMMON MATERIALS

Material Emissivity Material Emissivity

Aluminum 0.30 Glass 0.90 to 0.95
Asphalt 0.95 Iron Oxides 0.78 to 0.82
Concrete 0.95 Paint 0.80 to 0.95
Asbestos 0.95 Plastic 0.85 to 0.95
Ceramics 0.95 Paper 0.70 to 0.94
Brass 0.50 Plaster 0.80 to 0.90
Brick 0.90 Rubber 0.95
Carbon 0.85 Wood 0.90
Sludge 0.94 Textile 0.94
Frozen Food 0.90 Lead 0.50
Hot Food 0.93 Marble 0.94
Ice 0.98 Cloth (black) 0.98
Snow 0.90 Sand 0.90
Human Skin 0.98 Water 0.93

15

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IRT730K User’s Manual

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©2013 GENERAL TOOLS & INSTRUMENTS

MAN# IRT730K

10/24/13