HT Italia HT3320 User manual

©Copyright HT ITALIA 2011 Release EN 1.00 - 29/07/2011
ENGLISH
User manual

HT3320
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Table of contents:
1.PRECAUTIONS AND SAFETY MEASURES ...............................................................3
1.1.Preliminary instructions........................................................................................................3
1.2.During use............................................................................................................................4
1.3.After use...............................................................................................................................4
2.GENERAL DESCRIPTION...........................................................................................4
3.PREPARATION FOR USE...........................................................................................5
3.1.Initial checks ........................................................................................................................5
3.2.Instrument power supply......................................................................................................5
3.3.Calibration............................................................................................................................5
3.4.Storage.................................................................................................................................5
4.NOMENCLATURE........................................................................................................6
4.1.Instrument description..........................................................................................................6
4.2.Description of function keys.................................................................................................6
4.3.Description of the symbols shown on the display ................................................................7
5.SETTING SYSTEM PARAMETERS.............................................................................8
5.1.Date/Time setting.................................................................................................................9
5.2.Measuring unit setting..........................................................................................................9
5.3.Language setting .................................................................................................................9
5.4.Font color setting ...............................................................................................................10
5.5.Cursor shape setting..........................................................................................................10
5.6.Backlight brightness percentage setting............................................................................10
5.7.Auto power off setting ........................................................................................................11
5.8.Display switching off setting...............................................................................................11
5.9.Key sound setting ..............................................................................................................11
5.10.Memory status setting........................................................................................................12
5.11.Default settings ..................................................................................................................12
6.SETTING MEASURING FUNCTIONS........................................................................13
6.1.Emissivity setting................................................................................................................13
6.2.Setting the maximum alarm temperature threshold...........................................................15
6.3.Setting the minimum alarm temperature threshold............................................................15
6.4.Laser pointer......................................................................................................................15
6.5.Continuous measurement..................................................................................................15
6.6.MAX/MIN display................................................................................................................16
6.7.Average/Difference display ................................................................................................16
6.8.air / %RH Temperature display ..........................................................................................16
6.9.Dew point / wet bulb temperature display..........................................................................16
6.10.Temperature display with K-type probe..............................................................................17
7.OPERATING INSTRUCTIONS...................................................................................18
7.1.Switching on/off the instrument..........................................................................................18
7.2.Instrument reset.................................................................................................................18
7.3.IR video mode....................................................................................................................19
7.4.Infrared temperature measurement ...................................................................................21
7.5.Dew point temperature measurement................................................................................22
7.6.Datalogger function............................................................................................................23
7.7.Temperature measurement with K-type probe...................................................................24
8.OPERATIONS WITH THE MEMORY.........................................................................25
9.CONNECTING THE INSTRUMENT TO THE PC.......................................................25
10.MAINTENANCE..........................................................................................................26
10.1.General ..............................................................................................................................26
10.2.Internal battery charge.......................................................................................................26
10.3.Cleaning the instrument.....................................................................................................26
10.4.End of life...........................................................................................................................26
11.TECHNICAL SPECIFICATIONS.................................................................................27
11.1.General characteristics ......................................................................................................27

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11.2.Environment.......................................................................................................................28
11.2.1.Environmental conditions .......................................................................................................28
11.3.Accessories provided.........................................................................................................28
11.4.Optional accessories..........................................................................................................28
12.SERVICE....................................................................................................................29
12.1.Warranty conditions ...........................................................................................................29
12.2.Service...............................................................................................................................29

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1. PRECAUTIONS AND SAFETY MEASURES
The instrument has been designed in compliance with the directives relevant to electronic
measuring instruments. For your safety and in order to prevent damaging the instrument,
please carefully follow the procedures described in this manual and read all notes
preceded by the symbol with the utmost attention.
The following symbol is used in this manual:
WARNING
When this symbol is displayed, the instrument is not able to emit a laser pointer.
Always prevent the laser from radiating to your eyes, in order to prevent
any injury. Class II laser device compliant with EN 60825-1.
1.1. PRELIMINARY INSTRUCTIONS
WARNING
•Use the instrument only as specified in this user manual. An improper use
may damage the instrument.
•During use and storage, keep the instrument away from direct sunlight or
sources of light, hot surfaces or objects, high temperatures, high humidity
or particularly critical environmental conditions.
•After a period of storage under extreme environmental conditions, let the
instrument resume normal operating conditions before using it.
•If the instrument is moved from a cold to a hot environment, some
condensation may appear on the focal lens which emits infrared rays Wait
for the condensation to dissipate before taking measurements.
•Do not touch the focal lens which emits infrared rays.
•Make sure that the target is larger than the unit’s spot size The smaller the
target, the closer you should be to it. When accuracy is critical, make sure
the target is at least twice as large as the spot size.
•Only the accessories provided together with the instrument will guarantee
safety standards. They must be in good conditions and replaced with
identical models, when necessary.
•Do not perform any measurements beyond the limits specified in chapter
11.
•Check that the battery is correctly inserted
•Do not carry out any measurement if you notice anomalous conditions such
as breakages, leakages of battery liquid, blind display, etc.
•This instrument is not recommended for use in measuring shiny or polished
surfaces (stainless steel, aluminum, etc.).
•The instrument cannot measure temperature through transparent surfaces
such as glass. The instrument will measure the surface temperature of the
glass instead.
•Steam, dust, smoke, etc. can prevent accurate measurement.

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1.2. DURING USE
Please carefully read the following recommendations and instructions:
WARNING
•Never press the Tkey when the laser is active and the instrument is directed
towards the eyes. The instrument emits a laser pointer
•If the object to be measured has a smooth surface reflecting the laser,
prevent the laser from radiating to our eyes.
•Never radiate the laser if flammable gas in present.
•If the " " symbol is displayed during use, interrupt testing and recharge
the battery according to the procedure described in § 10.2.
•Be extremely careful when the laser pointer is turned on.
1.3. AFTER USE
•When measurement is complete, switch off the instrument
•If you expect not to use the instrument for a long period, remove the battery
2. GENERAL DESCRIPTION
HT3320 is an innovative digital thermometer capable of carrying out infrared (IR)
temperature measurements of objects, also providing a visual display of the object thanks
to the in-built photo camera, perform IR videos, recording the temperature values (logger)
and measuring temperature using a K-type probe.
The characteristics of the instrument are:
¾IR temperature measurement with/without in-built visual photo camera
¾Distance / Spot ratio 50:1
¾Image saving in JPG format (640x480pxl)
¾Video saving in 3GP format
¾Air temperature/humidity measurement with in-built sensor
¾Temperature measurement of the dew point and of the wet bulb
¾Temperature measurement by means of external K-type probe
¾Datalogger function for temperature measure recording
¾Internal memory and external SD Card for measure saving
¾Modern and ergonomic design
¾Double built-in laser pointer
¾Automatic reading lock (HOLD)
¾Continuous measurements (Auto Mode)
¾Emissivity adjustable from 0.10 to 1.00
¾Selection of measuring unit °C /°F
¾Detection of MAX, MIN, DIF, AVG values
¾Setting of high and low alarm thresholds on temperature measurements
¾Backlit LCD display
¾Automatic power off
¾PC connection via USB cable for image/video/recording download

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3. PREPARATION FOR USE
3.1. INITIAL CHECKS
Before shipping, the instrument has been checked from an electric as well as mechanical
point of view.
However, we suggest you to check it rapidly, to detect possible damage which may have
occurred during transport.
In case anomalies are found, immediately contact the Dealer.
We recommend checking that the packaging contains all components indicated in § 11.3.
In case the instrument should be replaced, please carefully follow the instructions given in
§ 12.
3.2. INSTRUMENT POWER SUPPLY
The instrument is supplied by a rechargeable Li-ION 3.7V 1400mAh battery with AC mains
power supply, which also provides for the recharge of the mentioned battery. Both of these
systems are provided with the instrument. The battery can also be recharged by directly
connecting it to the PC via USB (see § 10.2).
3.3. CALIBRATION
The instrument has the technical specifications described in this manual. Its performance
is guaranteed for one year starting from the date of purchase.
3.4. STORAGE
In order to guarantee precise measurement, after a long storage time under extreme
environmental conditions, wait for the instrument to come back to normal condition (see
the environmental specifications contained in § 11.2).

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4. NOMENCLATURE
4.1. INSTRUMENT DESCRIPTION
CAPTION:
1. LCD display
2. Function keys (see § 4.2)
3. Battery compartment cover
4. Tkey (Trigger)
5. Lens protection cover
6. In-built photo camera
7. Double laser pointer
8. IR sensor
9. In-built sensor for
temperature/humidity
measurement
10.Connector for k-type
thermocouple insertion
11.USB interface
12.Slot for SD card insertion
13.Battery
Fig. 1: Instrument description
4.2. DESCRIPTION OF FUNCTION KEYS
CAPTION:
1. Key (Arrow/Photo
camera)
2. Key (ON/OFF and
ESC)
3. Key (Arrow/Video)
4. Key (ENTER)
Fig. 2: Description of function keys

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4.3. DESCRIPTION OF THE SYMBOLS SHOWN ON THE DISPLAY
Symbol Description Symbol Description
Photo camera activation Data freezing on the display
(HOLD – releasing of Tkey)
A
ctivation of IR temperature
measurement without photo
camera
A
larm for high temperature
threshold exceeded activated
A
ctivation of temperature
measurement of dew point Alarm for high temperature
threshold exceeded in
progress
Active laser pointer
A
larm for low temperature
threshold exceeded activated
Measurement performance
(Scan - pressure of Tkey)
A
larm for low temperature
threshold exceeded in
progress
AT Air Temperature DIF It indicates the difference
between two measured IR
temperature values
RH% Air relative humidity AVG It indicates the average value
among the measured IR
temperature values
DP Dew point temperature MIN It indicates the minimum value
among the measured IR
temperature values
WB Wet bulb temperature MAX It indicates the maximum
value among the measured IR
temperature values
TK It indicates the temperature
value measured with the K
probe
It indicates the current mode
of continuous measurement
(see § 6.5)
Table 1: Description of the symbols shown on the display

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5. SETTING SYSTEM PARAMETERS
Every time it is switched on, the instrument shows the following general menu
IR CAM
IR MEASURE
DEW POINT
DATALOGGER
DATA MEMORY
SETTINGS
Fig. 3: Instrument general menu
Select item “SETTINGS” using the arrow keys Sor Tand confirming with the ENTER
key. The following screen appears on the display:
SYSTEM SET SYSTEM SET
Date/Time Keypress Alert
Unit (°C /°F) Memory Status
Language Factory Settings
Font color
Cursor
Backlight
Auto Power Off
Screen Timeout
Fig. 4: System setting menu
Use the arrow keys Sor Tto select the items and confirm with ENTER to access the
relevant programming sections.

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5.1. DATE/TIME SETTING
In this section it is possible to set the system Date/Time. There are two options to set the
Time: “24 hours” (00-24 format) or AM/PM.
Date setting
1. Press the ENTER key to switch from a Date field to the other
2. Use the arrow keys Sor Tto set the Date values in format “DD-MM-YYYY”
3. Press the ESC key to save and exit the function
Time setting
1. Press the ENTER key to switch from a Time format to the other
2. Use the arrow keys Sor Tto set the Time values
3. Press the ESC key to save and exit the function
5.2. MEASURING UNIT SETTING
In this section it is possible to set the temperature measuring unit either in °C (Celsius) or
°F (Fahrenheit)
1. Use the arrow keys Sor Tto select the option °C or °F (see Fig. 5)
2. Press the ESC key to save and exit the function
Fig. 5: Selection of the measuring unit
5.3. LANGUAGE SETTING
In this section it is possible to set the system language, choosing among the available
options
1. Use the arrow keys Sor Tto select the desired language (see Fig. 6)
2. Press the ESC key to save and exit the function
Fig. 6: System language selection

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5.4. FONT COLOR SETTING
In this section it is possible to set the color of the font shown on the instrument’s display
1. Use the arrow keys Sor Tto select the desired color, choosing among the available
options: Orange, Green, Black, Blue, Gold and Purple (see Fig. 7)
2. Press the ESC key to save and exit the function
Fig. 7: Font color selection
5.5. CURSOR SHAPE SETTING
In this section it is possible to set the shape of the central cursor (if required) associated
with the IR sensor
1. Use the arrow keys Sor Tto select the options: Off (no cursor), Cross, Circle (see
Fig. 8)
2. Press the ESC key to save and exit the function
Fig. 8: Selection of measuring cursor shape
5.6. BACKLIGHT BRIGHTNESS PERCENTAGE SETTING
In this section it is possible to set the brightness percentage of the display’s backlight
1. Use the arrow keys Sor Tto select the options from 30% (minimum brightness) to
100% (maximum brightness) (see Fig. 9)
2. Press the ESC key to save and exit the function
Fig. 9: Backlight percentage selection

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5.7. AUTO POWER OFF SETTING
In this section it is possible to disable the Auto Power Off function of the instrument or to
set a value among the available ones
1. Use the arrow keys Sor Tto select the options: Disabled, 3 Min, 15 Min or 60 Min
(see Fig. 10)
2. Press the ESC key to save and exit the function
Fig. 10: Auto Power Off setting selection
5.8. DISPLAY SWITCHING OFF SETTING
In this section it is possible to disable the automatic switching off function of the display
(the function may be enabled again by pressing any key) or to choose a time value among
the available ones
1. Use the arrow keys Sor Tto select the options: Disabled, 30s, 1 Min or 2 Min (see
Fig. 11)
2. Press the ESC key to save and exit the function
Fig. 11: Display switching off setting selection
5.9. KEY SOUND SETTING
In this section it is possible to disable/enable the sound associated with the pressure of the
function keys of the instrument
1. Use the arrow keys Sor Tto select the options: Disable, Enable (see Fig. 12)
2. Press the ESC key to save and exit the function
Fig. 12: Key sound setting selection

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5.10. MEMORY STATUS SETTING
In this section it is possible to select the type of memory (internal or SD Card) in which to
save the measured data. The instrument also provides indications on the used and on the
free memory space.
1. Use the arrow keys Sor Tto select the options: Device memory, SD Card (see Fig.
13)
2. Press the ENTER key to format the internal memory or the SD Card. Press the down
arrow key Tto confirm the operation or the up arrow key Sto cancel the operation.
3. Press the ESC key to save and exit the function
Fig. 13: Memory selection for data saving
WARNING
Use a micro SD Card with a maximum capacity of 8GB
5.11. DEFAULT SETTINGS
This section allows automatically setting the factory-set default conditions on the
instrument, as described in Table 2
Parameter Default value Parameter Default value
Emissivity 0.95 Measuring unit °C
HIGH alarm Enabled Language English
LOW alarm Enabled Character color Orange
Laser Enabled Cursor Circle
Continuous
measurement Disabled Backlight 100%
MAX/MIN Enabled Automatic power off 3 min
Average/Difference Enabled LCD switching off 30s
AT / RH% Enabled Key sound Disabled
DP / WB Enabled Memory status Internal
K type Enabled Language English
Table 2: Parameter default values

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6. SETTING MEASURING FUNCTIONS
In each measuring mode (see § 7), by pressing the ENTER key, the instrument shows the
following screen:
MEASURE SET MEASURE SET
Emissivity Dewpoint / Wetbulb
Alarm High Type K
Alarm Low
Laser
Auto Mode
Max/Min
Average/Diff
Ambient Temp. / %RH
Fig. 14: Measurement setting menu
Use the arrow keys Sor Tto select the items and confirm with ENTER to access the
relevant programming sections.
6.1. EMISSIVITY SETTING
The radiating power or emissivity “
ε
” is a value between 0 and 1 which indicates the
capacity of an object to emit energy in the infrared frequency range. This parameter
depends both on the material the object is made of and on the finishing (painting).
Parameter “
ε
” is set by default to 0.95 because, in practice, it has been established that
approx. 90% of the objects have such a radiating power.
1. Select the first item (ε= x.xx) and press the ENTER key to set emissivity (see Fig. 15
and Table 3). Use the arrow keys Sor Tto set the value and then the ENTER key to
confirm
2. Use the arrow keys Sor Tto select one of the common materials listed below, among
the options: Concrete, Glass, Human skin, Ice/Water, Plastic, Wood
3. Press the ESC key to save and exit the function
Fig. 15: Emissivity setting menu

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Material Emissivity Material Emissivity
Zinc (oxidized) 0.1 (*) Carbon 0.95
Iron (polarized) 0.3 Red brick (rough) 0.75 - 0.9
Tin-plated steel 0.1 (*) Fire clay 0.75
Gold (polished) 0.1 (*) Asbestos 0.95
Silver (polished) 0.1 (*) Cast iron (at 100°C) 0.45
Chromium (polished) 0.1 (*) Cast iron (at 1000°C) 0.6 – 0.7
Steel (ground sheet) 0.6 Zirconium 0.85
Steel (oxidized) 0.9 Wrought iron 0.95
Liquid iron 0.9 Aluminium (polished) 0.1 (*)
Oxidized aluminium 0.25 Oxidized aluminium at 260°C 0.6
Oxidized aluminium at
800°C 0.3 Brass (polished) 0.1 (*)
Brass (rough) 0.2 Brass (oxidized) 0.6
Copper (polished) 0.05 (*) Copper (oxidized) 0.8
Molten copper 0.15 Lead (pure) 0.1 (*)
Lead (oxidized at 25°C) 0.3 Lead (oxidized at 200°C) 0.6
Nickel (pure) 0.1 (*) Nickel-Chromium 0.7
Nick-Chromium (oxidized) 0.95 Mortar 0.89 .. 0.91
Marble 0.9 Plaster 0.9
Alumina (fine grain) 0.25 Alumina (coarse grain) 0.45
Silica (fine grain) 0.4 Silica (coarse grain) 0.55
Quartz (rough) 0.9 Graphite 0.75
Timber 0.8 - 0.9 Enamel (any color) 0.9
Paint (any color) 0.95 Lacquer 0.9
Water 0.98 Rubber (smooth) 0.9
Rubber (rough) 0.98 Plastic (various) 0.8 - 0.95
Paper 0.9 Silicone 0.7
Asphalt 0.90 .. 0.98 Cloth (black) 0.98
Concrete 0.94 Human skin 0.98
Cement 0.96 Leather 0.75 .. 0.80
Sand 0.90 Charcoal powder 0.96
Earth 0.92 .. 0.96 Glass 0.90 .. 0.95
Water 0.92 .. 0.96 Ceramic 0.90 .. 0.94
Ice 0.96 .. 0.98 Rubber 0.94
Snow 0.83 Plastic 0.85 .. 0.95
(*) Emissivity variable with point
Table 3: Emissivity values of materials

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6.2. SETTING THE MAXIMUM ALARM TEMPERATURE THRESHOLD
The instrument is provided with an acoustic alarm on IR temperature measurements; the
alarm sounds when a maximum threshold which can be set up to 1000°C is exceeded.
1. Use the arrow keys Sor Tto enable/disable the alarm (see Fig. 16)
2. With enabled alarm, press the ENTER key and then use the arrow keys Sor T(press
and hold the keys to quickly scroll the values) to set the threshold value. Press ENTER
again to confirm.
3. Press the ESC key to save and exit the function
Fig. 16: Menu for setting the maximum alarm threshold
6.3. SETTING THE MINIMUM ALARM TEMPERATURE THRESHOLD
The instrument is provided with an acoustic alarm on IR temperature measurements, for
values below a minimum threshold which can be set up to -50°C.
1. Use the arrow keys Sor Tto enable/disable the alarm (see Fig. 17)
2. With enabled alarm, press the ENTER key and then use the arrow keys Sor T(press
and hold the keys to quickly scroll the values) to set the threshold value. Press ENTER
again to confirm.
3. Press the ESC key to save and exit the function
Fig. 17: Menu for setting the minimum alarm threshold
6.4. LASER POINTER
In this section it is possible to enable/disable the double laser pointer which can be used in
IR temperature measurements.
1. Use the arrow keys Sor Tto select the options: Disable, Enable (see Fig. 18)
2. Press the ESC key to save and exit the function
Fig. 18: Laser pointer activation menu
6.5. CONTINUOUS MEASUREMENT
In this section it is possible to enable/disable the continuous measurement mode of IR
temperature by the instrument with no need to press the Tkey.
1. Use the arrow keys Sor Tto select the options: Disable, Enable (see Fig. 19)
2. Press the ESC key to save and exit the function
Fig. 19: Continuous measurement activation menu

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6.6. MAX/MIN DISPLAY
In this section it is possible to enable/disable the display of the Max and Min values of IR
temperature.
1. Use the arrow keys Sor Tto select the options: Off, On (see Fig. 20)
2. Press the ESC key to save and exit the function
Fig. 20: Max/Min display activation menu
6.7. AVERAGE/DIFFERENCE DISPLAY
In this section it is possible to enable/disable the display of the Average and Difference
values of the IR temperature measured by the instrument.
1. Use the arrow keys Sor Tto select the options: Off, On (see Fig. 21)
2. Press the ESC key to save and exit the function
Fig. 21: Average/Difference display activation menu
6.8. AIR / %RH TEMPERATURE DISPLAY
In this section it is possible to enable/disable the display of the air temperature values and
of the relative humidity measured by the internal sensor of the instrument.
1. Use the arrow keys Sor Tto select the options: Off, On (see Fig. 22)
2. Press the ESC key to save and exit the function
Fig. 22: Air temperature/humidity display activation menu
6.9. DEW POINT / WET BULB TEMPERATURE DISPLAY
In this section it is possible to enable/disable the display of the dew point and wet bulb
temperature values measured by the instrument.
1. Use the arrow keys Sor Tto select the options: Off, On (see Fig. 23)
2. Press the ESC key to save and exit the function
Fig. 23: Dew point/wet bulb temperature display activation menu

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6.10. TEMPERATURE DISPLAY WITH K-TYPE PROBE
In this section it is possible to enable/disable the display of the temperature values
measured with the k-type probe.
1. Use the arrow keys Sor Tto select the options: Off, On (see Fig. 24)
2. Press the ESC key to save and exit the function
Fig. 24: Activation menu for display of temperature values measured with K-type probe
WARNING
By inserting the K-type thermocouple (see § 7) the instrument automatically
enables temperature measurement with K probe, whose display can be disabled
by the user.

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7. OPERATING INSTRUCTIONS
Upon start-up, the instrument shows the following 6 operating modes, which can be
selected through the arrow keys Sor T, confirming with ENTER
IR VIDEO
IR MEASURE
DEW POINT
DATALOGGER
DATA MEMORY
SETTINGS
Fig. 25: Instrument general menu
MEASURING
MODE DESCRIPTION
IR VIDEO IR temperature measurement with in-built photo camera + IR video recording + relative air temperature/humidity measurement with
internal sensor (see § 7.3)
IR MEASURE IR temperature measurement without saving (see § 7.4)
DEW POINT IR temperature measurement + dew point temperature (see § 7.5)
DATALOGGER Recording of temperature measurement with setting of time scan
and alarm conditions (see § 7.6)
DATA MEMORY It allows displaying and deleting images, videos and recordings
saved in the instrument (see § 8)
SETTINGS It allows setting the instrument’s system parameters (see § 5)
7.1. SWITCHING ON/OFF THE INSTRUMENT
1. To switch on the instrument, press and hold the key until the general menu is
displayed
2. Press and hold the key until the display switches off
7.2. INSTRUMENT RESET
In case all functions on the display get stuck, the instrument allows carrying out a
Hardware Reset operation, in order to restore normal operation. Proceed as follows:
1. Use the tip of a pencil or of another object, slightly touching the inner part of the hole
next to the USB port labeled “RESET”
2. The instrument switches off automatically and can be switched on again The RESET
operation does not delete any data from the memory

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7.3. IR VIDEO MODE
This mode allows carrying out IR temperature measurement with the in-built photo
camera, saving the images in standard JPG format, recording IR videos of IR temperature
measurements saving them in 3GP format, measuring the air temperature/humidity with
the in-built sensor and measuring temperature with type K probe (if enabled – see § 6.10)
1. Switch on the instrument and enter the “VIDEO IR” mode
2. Set the desired values of the measurement parameters (see § 6)
3. Hold the meter and point it towards the object whose temperature is to be measured.
The object will appear on the display because of the in-built photo camera
4. Press and hold the Skey to perform a zoom operation of the imagine at display and
press and hold the Tkey to restore the normal sizes of the imagine at display
5. Press and hold the Tkey to start measuring, observing on the display the symbol
and the temperature value in the middle of the display, which varies in real time (see
Fig. 26)
Fig. 26: IR temperature measurement with in-built photo camera
6. Release the Tkey to stop the measurement and freeze the last read value. The display
shows the following symbol “ ”. The temperature values associated with fields AT,
RH%, DP and WB, if selected (see § 6.8, 6.9) are shown on the display.
7. Fig. 27 shows the ratio between distance of the instrument from the object being
measured and the spot size. As the distance (D) from the object increases, the spot
size (S) becomes larger. The focal point of the instrument is 914mm (36”). The
displayed spot sizes indicate the areas which include 90% of the detected energy.
Fig. 27: Diameter of surface S with reference to the distance D from the object (in mm)