METIS M311 / M322 / H311 / H322 (17-pin)
Mechanical Installation
15
5.3
Ambient Temperature
The M311 and M322 pyrometers are designed for ambient temperatures between 0 and 80°C, H3 mod-
els for ambient temperatures between 0 and 60°C.
To prevent it’s overheating, the camera module of M3 models is switched off from 55°C device tempera-
ture (is not applicable for H3 devices). The laser of laser targeting light models is deactivated at a de-
vice temperature above 65°C (M3 devices) or 60°C (H3 devices). Below that temperature it can be used
again.
Fiber optic devices can be exposed on optics and optical fiber to ambient temperatures between -20
and 250°C without cooling, for the housing the same temperatures apply as for standard devices (0
–
80°C).
Operation outside this temperature leads to incorrect measurements and may damage the unit.
To comply with the permitted ambient temperature sufficient distance from the (hot) measuring object is
observed.
The internal housing temperature can be read out via the soft-
ware
SensorTools
(see
).
It is also possible to configure one of the digital (switching) out-
puts in such a way that a corresponding signal is switched if ex-
ceeding the maximum temperature (see
puts / Outputs
and under
).
Accessory:
With radiant heat from the front, the pyrometer can be protected by a cooling plate. The
use of the pyrometer in ambient temperatures outside the permissi
ble pyrometer’s ambient temperature
is possible with an additional cooling housing.
5.4
Ratio Technology / Alignment onto the Measuring Object
In opposition to radiation pyrometers, 2-color pyrometer measure in two spectral ranges simultaneously
(Two separate detectors at two adjacent narrow-band wavelengths) and determine the temperature by
forming the radiation ratio (quotient).
In this method it is not necessary to know the emissivity of the target material. It cancels out because
the radiation ratio remains constant at a neutral attenuation of infrared radiation (by dust, smoke ...).
However, this reduction will only be successful if signal attenuation occurs homogeneously on both
wavelength ranges. If the emissivity change in the two wavelengths e.g. with increasing temperature,
also the relationship changes which results in measurement errors.
Via the Software
SensorTools
the 2-color temperature and the temperatures of the individual channels
can be shown simultaneously to identify possible wavelength dependence (see
).
To detect the temperature correctly, the pyrometer
must be properly aligned to the measuring object. In
the focus point of the optics (focus distance) the spot
size diameter is the smallest. Also measurements in
the defocused area can be done to determine the av-
erage temperature of a bigger spot.
To get a correct measurement result, the following
requirements must be observed:
For measurements through window, the window material has to be observed. If the transmission
properties are not uniform (e.g. quartz glass), the corresponding emissivity slope has to be entered.
The distance to the measured object must be in the range of focusable measurement distance of the
optics, if a precise spot measurement has to be made.
If the target is smaller than the spot size diameter, a
warm background temperature effects the measure-
ment. But these shows until about 300°C an impact and
about that the influence is also slight.
Spot size bigger
Focus point
Spot size smaller than measuring object
Measuring object
Pyrometer
’s spot size bigger than measur-
ing object, note background radiation.
DT: internal de-
vice temperature
via software