Extech 45158 Anemometer 45158 Scheda Tecnica

  User Manual 

Model 45158                            

 

Congratulations on your purchase of Extech’s Model 45158 Anemometer. The dual 

display indicates Air Velocity and Humidity, Dew Point, Ambient Temperature, or 

Temperature with wind-chill factor. With careful use, this meter will provide years of 

reliable service. 

•  Press the ON/OFF/HOLD button to turn the meter ON 

•  Press and hold the ON/OFF/HOLD buttons for approx. 3 seconds to turn it OFF 

•  The meter’s Auto Power OFF feature turns the meter OFF after 20 minutes of inactivity 

•  With the meter ON, press and hold down the ON/OFF/HOLD button 

•  While continuing to hold the ON/OFF/HOLD button, press the UNITS/MODE button 

repeatedly to step through Temperature (oF/oC), Humidity (RH%), Dew Point (TD), & 

Temperature with wind-chill factor (WCI). Note that the center display is Air Velocity. 

•  Turn the meter OFF. Press and hold down both buttons until the display turns on and 

begins blinking then release both buttons 

•  Press the UNITS/MODE button repeatedly to step through the units (see specs for list) 

•  After 5 seconds the meter switches back to normal operation mode automatically 

•  Turn the meter OFF first. Press and hold down both buttons until the display turns on 

and begins blinking then release the buttons 

•  Press both buttons momentarily to change temperature units 

•  After 5 seconds the meter switches back to normal operation mode automatically 

•  Position the meter so that the airflow enters the meter vane from the rear of the meter 

(opposite side of front panel logo). A tripod mount is located on the bottom of the meter. 

•  Max Hold represents the highest measurement taken since the meter was turned on 

•  Press the UNITS/MODE button to display the Max reading (MAX icon appears) 

•  Press the UNITS/MODE button repeatedly to step through to the normal operating 

mode  

•  5 or 10 reading averages can be displayed in the Average Mode. 

•  Press UNITS/MODE 3 times for 5 reading averaging or 4 times for 10 readings 

•  To exit this mode, press the UNITS/MODE button until the icons on the left disappear 

•  Data Hold freezes the most recent displayed reading 

•  Press and hold the ON/OFF/HOLD button to activate Data Hold 

•  As long as the ON/OFF/HOLD button is held the reading will remain on the LCD 

 

 

1 

Vane impeller 

2 

Impeller set screw (on rear of meter) 

3 

Relative Humidity sensor 

4 

Temperature sensor 

5 

LCD display 

6 

ON/OFF, HOLD key  

7 

UNITS, MODE key 

8 

Battery compartment (on rear) 

9 

Tripod mounting hole 

10 

Lanyard (neckstrap) 

 

MPH (Miles per hour)  1.1 to 62.5 MPH 

0.2 MPH 

± (3% + 0.4 mph) 

km/hr (kilometers per 
hour) 

1.8 to 100.6 km/h 

0.7 km/h 

± (3% + 1.4 km/hr) 

Knots (nautical miles 

per hour) 

1.0 to 54.3 knots 

0.3 knots 

± (3% + 0.6 knots) 

m/sec (meters per 

second) 

0.50 to 28.00 m/s 

0.01 m/s 

± (3% + 0.2 m/s) 

ft/min (feet per 

minute) 

100 to 5500 ft/min 

20ft/min 

± (3% + 40 ft/min) 

Beaufort force 

1 to 17 BF 

1 BF 

± 1 

Temperature 

0 to 122

o

F (-18 to 50

o

C) 0.1

o

F/C ± 

1.8

o

F (± 1

o

C) 

Relative Humidity 

10 to 95% 

1% 

± 5% RH 

Dew Point 

32 to 122

 o

F (0 to 50

o

C) 0.1

o

F/C ± 

3.6

o

F (2

o

C) 

Display 

Dual LCD with low battery and multifunction indicators 

Sensors 

Sapphire bearing, non-corrosive vane for air velocity; 

Precision thermistor for temperature measurements 

Average Mode 

Choice of 5 or 10 reading averaging (2 second factory 

default) 

Max and Data Hold 

Displays 

Max recalls the highest reading; Data Hold freezes the 

display 

Sample time 

1 reading per second for air velocity and temperature 

(1 reading per 15 seconds for humidity with 2 second 

updates) 

Water-resistant 

To 3’ (1m) 

Operating conditions 

5 to 122

o

F (-15 to 50

o

C) / < 80% RH 

Power supply 

Lithium battery (CR-2032 or equivalent) / 400 hour battery 

life 

Dimensions / Weight 

Instrument:  5.25 x 2.75 x 0.75” (133 x 70 x 19mm) 
Vane: 1” ( 24mm ) diameter / 3 oz. ( 95 g ) 

 

The 45158 has a low battery indicator (battery symbol). 
Important: Turn the meter off before opening the battery 
compartment. Using a coin, turn the battery compartment cover 
CLOCKWISE to remove it. Once opened, observe the position of 
the battery, placing the new one in the same position. Secure the 
battery compartment cover and dispose of the lithium battery in 
accordance with local, state, or national disposal codes. 

 

You, as the end user, are legally bound (Battery 
ordinance) to return all used batteries and 
accumulators; disposal in the household garbage is 
prohibited! 

You can hand over your used batteries / accumulators, 
gratuitously, at the collection points for our branches in 
your community or wherever batteries / accumulators 
are sold! 

Follow the valid legal stipulations in respect of the 
disposal of the device at the end of its lifecycle 

 

 

•  Remove the set screw next to the impeller assembly (on the 

rear of the meter).  

•  Twist the impeller assembly counter-clockwise to the OPEN 

position and remove it. 

•  Install impeller by inserting & twisting the new impeller 

assembly clockwise 

•  Tighten the set screw. 

Measure the area of the duct using the diagrams below for rectangular and circular ducts (If 

the duct measurements are made in inches, divide the inches by 144 to get the area in 

square feet). Plug the area value (in square feet) in the cubic equations below. Note that 
the air velocity must be plugged into the cubic equations also. 

 

CFM (ft

3

/min) = Air Velocity (ft/min) x Area (ft

2

) 

CMM (m

3

/min) = Air Velocity (m/sec) x Area (m

2

) x 60 

Copyright © 2007 Extech Instruments Corporation.