Extech Instruments HD550 User manual

User Guide
Heavy Duty Psychrometer + IR Thermometer
Model HD550

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Introduction
Congratulations on your purchase of the Extech HD550 Psychrometer. This handheld meter
measures and displays Air Temperature, Dew Point Temperature, and Wet Bulb Temperature;
Humidity in %RH, grains per pound, and grams per kilogram; and Surface Temperature using the
built-in IR thermometer. This meter is shipped fully tested and calibrated and, with proper care
and use, will provide years of reliable service.
Features
Triple digital LCD display.
Fast response, all data is calculated four times per second.
Standard type K (NiCr-NiAl) Thermocouple input jack suitable for any style of type K probe.
Infrared thermometer to measure surface temperature.
Red laser pointer included.
LCD with Backlight.
Automatic range selection.
USB interface.
Low battery indication.
Auto Power off.
Safety
Use extreme caution when the laser pointer beam is on
Do not point the beam toward anyone's eye or allow the beam
to strike the eye from a reflective surface
Do not use the laser near explosive gases or in other
potentially explosive areas

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Meter Description
1. Humidity & Air Temperature Sensor
2. Type K Thermocouple input jack
3. Laser pointer beam
4. IR temperature sensor
5. USB Interface
6. LCD Display
7. Upper display HOLD button
8. UNITS button for Temperature/ Wet Bulb/ Dew Point/
%RH/GPP/ g/kg
9. Upper display record Max/Min button
10. IR Measurement button
11. °F/°C units button
12. Lower display HOLD button
13. Lower display record Max/Min button
14. Backlight button
15. Power button
NOTE: Battery Compartment, Tilt Stand and Tripod Mount are located on the reverse side of
the meter
Display Description
1. Low Battery icon
2. PC communication icon
3. Upper display function icons
4. Upper display
5. Laser pointer icon
6. Lower display function icons
7. Lower display
8. Lower display function icons
GPP
g/kg

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Operation
Basic Measurements
1. Press the button to turn power on.
2. Press the °C/°F button to change the units of measure from °C or °F.
3. The upper display will indicate Air Temperature, Wet Bulb Temperature or Dew Point
Temperature and % Relative Humidity, or Air Temperature and Grains Per Pound, or grams per
kilogram. Press the UNITS button to toggle between Air, WB or DP, and %RH, GPP or g/kg.
4. The lower display will indicate Type K temperature or IR Temperature. Press and hold the IRT
button to select the IR Thermometer. The TYPE-K function will display “-------“ if a type k probe is
not inserted into the meter.
Non-contact IR Surface Temperature Measurements
The built-in IR sensor can remotely measure the temperature of most surfaces. The
Laser pointer allows the user to aim accurately when taking non-contact
measurements.
1. Turn ON the meter using the button.
2. The IR sensor and laser pointer are located at the top of the meter.
3. Point the sensor toward the surface to be measured.
4. Press and hold the IRT button to begin measuring the surface temperature of a
desired target. IR TEMP and will appear on the display. The laser pointer will
switch on to help aim the meter.
5. The measured IR surface temperature will appear on the lower display.
6. When the IRT button is released, the laser pointer will switch off and the reading
will freeze (data hold) on the display for approximately 7 seconds.
7. After the 7 second hold time the meter returns to the type K mode.
WARNING: Do not directly view or direct the laser pointer at an eye. Low power visible lasers
do not normally present a hazard, but may present some potential for hazard if viewed directly for
extended periods of time.

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Data Hold
1. Press the HOLD button (one for upper display and one for lower display) to freeze the displayed
value for the respective display. Press again to unlock the display.
2. The HOLD icon will appear on the display when the Data Hold mode is active.
MIN-MAX Recording Mode
1. Press the MAX/MIN button (one for upper display and one for lower display) to begin recording
the Maximum and Minimum reading. The REC MAX icon will appear and only the maximum
value measured will appear in the display. The display will update only if a value higher than the
currently displayed value is measured.
2. Press the MAX/MIN button again to display the minimum values. The REC MIN icon will appear
and only the minimum recorded value will appear in the display.
3. Press the MAX/MIN button again to display the currently measured values. The REC icon will
appear in the display and the Max and Min values will be stored in memory.
4. Press and Hold the MAX/MIN button for >2 seconds to exit the mode.
Auto-Power Off
The meter will automatically turn off after 15 minutes of operation if no buttons are pressed during
this period. Auto-power off can be disabled by:
Holding the IRT button and then pressing the button to turn the power on. When “disAPO”
appears in the display, release the IRT button and the APO will be disabled.
Low Battery
When the battery reaches the minimum operating voltage the battery icon will appear in the display.
Replace the 9V battery when this occurs.
Battery Replacement
When the battery icon appears on the LCD, the 9V battery must be replaced.
1. The battery compartment is located on the rear of the meter.
2. Press in and down on the arrow located above the tilt stand hinge.
3. Replace the 9V battery.
4. Replace the battery cover.
Backlight
Press the backlight button to turn the backlight ON or OFF.
Note: Continuous use of the backlight function will reduce battery life.
USB Interface and Software
The HD550 is equipped with a communication jack on its upper left side. The supplied
communications cable connects to this jack and to a USB port on a PC. The supplied software
allows the user to view and save readings to the PC. Instructions for use and features are detailed
in the supplied software HELP utility.

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InfraRed Measurement Considerations
When taking IR measurements the meter automatically compensates for ambient temperature
changes. Note that it may take up to 30 minutes to adjust to extremely wide ambient changes.
Low temperature measurements quickly followed by high temperature measurements may
require several minutes to stabilize as a result of the IR sensor cooling process.
If the surface of the object under test is covered with frost, oil, grime, etc., clean before taking
measurements.
If an object's surface is highly reflective apply masking tape or flat black paint before measuring.
Steam, dust, smoke, etc. can obstruct measurements.
To find a hot spot, aim the meter outside the area of interest then scan across (in an up and
down motion) until the hot spot is located.
IR measurements cannot be made through glass.
IR Theory
IR thermometers measure the surface temperature of an object. The meter’s optics sense emitted,
reflected, & transmitted energy that is collected and focused onto the meter’s detector. The meter’s
circuitry translates this information into an LCD reading.
IR Field of View
Ensure that the desired target is larger than the spot size. As the distance from an object increases,
the spot size of the area measured by the meter becomes larger. The meter’s field of view ratio is
30:1, meaning that if the meter is 30 inches (cm) from the target, the diameter (spot) of the object
under test must be at least 1 inch (cm). Refer below to the field of view diagram.
Emissivity
Most organic materials and painted or oxidized surfaces have an emissivity of 0.95. Inaccurate
readings will result when measuring shiny or polished surfaces. To compensate, cover the surface
under test with masking tape or flat black paint. Allow time for the tape to reach the same
temperature as the material underneath then measure the temperature of the tape or the painted
surface.

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Thermal Emissivity Table for Common Materials
Material Emissivity Material Emissivity
Asphalt 0.90 to 0.98 Cloth (black) 0.98
Concrete 0.94 Human skin 0.98
Cement 0.96 Leather 0.75 to 0.80
Sand 0.90 Charcoal (powder) 0.96
Earth 0.92 to 0.96 Lacquer 0.80 to 0.95
Water 0.67 Lacquer (matt) 0.97
Ice 0.96 to 0.98 Rubber (black) 0.94
Snow 0.83 Plastic 0.85 to 0.95
Glass 0.85 to 1.00 Timber 0.90
Ceramic 0.90 to 0.94 Paper 0.70 to 0.94
Marble 0.94 Chromium oxides 0.81
Plaster 0.80 to 0.90 Copper Oxides 0.78
Mortar 0.89 to 0.91 Iron Oxides 0.78 to 0.82
Brick 0.93 to 0.96 Textiles 0.90
Specifications
General Specifications
Display Dual Display Multi-function LCD with 9999 counts
Data Hold Freezes displayed reading
Sampling rate 1 reading per second
Sensors Relative Humidity: Capacitance type / Air Temp: Thermistor
IR Distance to Spot ratio 30:1
IR Spectral response 6 to 14µm
IR Emissivity 0.95 fixed
MIN-MAX Record and Recall lowest and highest readings
Auto Power OFF Automatic shut off after 15 minutes (can be disabled)
PC Interface USB PC Communication with supplied software and cable for data
acquisition (software HELP utility contains User Guide)
Over range indication Dashes appears on the LCD
Low battery indication Battery symbol appears on the LCD
Power supply 9V Battery
Operating conditions Meter: 0 to 50oC (32 to 122oF); 80% RH max.
Dimensions / Weight Main instrument: 257 x 76 x 53mm (10.1 x 3.0 x 2")
Weight 355g. (12.5 oz)

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Range Specifications
Function Range Resolution Accuracy
-148°F to -20°F (3.0% reading + 4°F)
-20°F to 2501°F (3.0% reading + 2°F)
-100°C to -30°C (3.0% reading + 2°C)
Temp
(type-K)
-30°C to 1372°C
1°≥1000
0.1°<1000
(3.0% reading + 1°C)
-58 to -4°F
-50 to -20°C 0.1°F/°C ±9.0°F / 5.0°C
IR Temp
-4 to 932°F
-20 to 500°C 0.1°F/°C ±2% reading or
±4°F/2°C
Air Temp. -4 to 140°F
-20 to 60°C 0.1°F/°C ±(2% reading +
2°F/1°C)
10% to 90% 0.1%RH ±2% RH%RH
<10% and >90% 0.1%RH ±3% RH
Wet Bulb -6.88 to 140°F
-21.6 to 60°C 0.1°F/°C
Dew Point -90.4 to 140°F
-68 to 60°C 0.1°F/°C
GPP 0 to 999 GPP 0.1 GPP <100 GPP
1 GPP >100 GPP
g/kg 0 to 160 g/kg 0.1 g/kg<100 g/kg
1 g/kg>100 g/kg
Calculated from RH
and air temperature
measurements
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