Velleman DVM8861 - Manual (Page 6)

DVM8861
00 (16/10/2008)
6
•
When a preset alarm limit is exceeded, an audible alarm signal will be produced, and
the according alarm icon in the display (D) will flash.
•
When the lock mode is enabled a small icon is shown in the display (C). The
thermometer will continuously measure the temperature until the measurement
trigger (6) is pulled a second time.
• During lock measurement, the emissivity can be changed with the up (3) and down
(4) button.
• Push the down button (4) once to switch on the backlight. Push again to switch it off.
•
Push the up button (3) once to switch on the laser beam. Push again to switch it off.
The laser beam is only an aiming aid, be careful when using it. Refer to the safety
instructions.
Notes:
• The unit will not measure correctly through transparent surfaces (e.g. glass), as it will
measure the surface temperature of the transparent surface.
• Steam, dust, smoke etc. will have a negative impact on the measurements accuracy.
• Measurements on shiny and/or polished surfaces will be inaccurate.
6. Background information
Working principle
The Infra Red sensor of the unit detects energy that is emitted, reflected and
transmitted by a surface. This energy is focussed onto a detector that converts this
information into a temperature reading. The laser beam is only used for aiming
purposes.
Ambient temperature
The thermometer automatically compensates ambient temperature conditions. Allow
the thermometer to stabilise to ambient temperature for at least 30 minutes for
accurate measurements.
Surface temperature
When going from low temperature to high temperature measurements or vice versa,
the IR sensor of the thermometer needs a few minutes to adjust.
Distance and spot size
As the distance (D) from the object increases, the spot size (S) of the area measured
by the unit becomes larger. The focal point for each unit is 914mm (36”).
D:S=12:1
D
S
12in. 1in @ 6in. 0.5in @
25mm @ 300mm 150mm 12.5mm @
Emissivity
Emissivity describes the energy-emitting characteristics of materials. Most organic or
oxidized surfaces have an emissivity of ±0.95 (default setting). Measuring shiny or