Extech Instruments EX845 User Manual page 8

Non-Contact InfraRed Temperature Measurements
1. Set the function switch to the IR Temp
position.
2. Aim the infrared sensor (rear of the meter) at
the surface to be measured.
3. Press the button in the center of the rotary
function switch to turn on the laser pointer and
identify the surface spot to be measured.
4. The area of the surface to be measured must
be larger than the spot size as determined by
the distance to spot size specification.
5. Read the temperature in the display.
Note: See the "Temperature Units" paragraph to select
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.
IR Spot to Distance Diagram
The 8:1 spot to distance ratio determines the size of the measured surface area with
respect to the distance the meter is held away from the surface.
10cm
IR Measurement Notes
1. The object under test should be larger than the spot (target) size calculated by the
field of view diagram.
2. If the surface of the object under test is covered with frost, oil, grime, etc., clean
before taking measurements.
3. If an object's surface is highly reflective, apply masking tape or flat black paint to the
surface before measuring.
4. The meter may not make accurate measurements through transparent surfaces such
as glass.
5. Steam, dust, smoke, etc. can obscure measurements.
6. 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.
o o
F or
Diameter of spot
7.5cm
2.5cm
1.25cm
20cm
60cm
Distance to object
8
C
EX845-EN V2.1 02/10