Ambient Temperature; Ratio Technology / Alignment Onto The Measuring Object - KPM PROCESS SENSORS METIS M311 Operating Manual

5.3

Ambient Temperature

▪ M311 and M322 pyrometers are designed for ambient temperatures between 0 and 80°C / 32 and 176°F.
▪ H3 models for ambient temperatures between 0 and 60°C / 32 and 140°F.
▪ Fiber optics and optical fiber of fiber optic devices can be exposed to ambient temperatures between -
20 and 250°C (-4 to 482°F) on the optics side and up to 120°C (248°F) on the housing side. The tempera-
tures for the housing are the same as for the standard devices.
INFO
to avoid overheating of the laser targeting light or camera module:
▪ The laser targeting light is deactivated at an internal device temperature above 65°C / 149°F (M3 devices) or
above 60°C / 140°F (H3 devices).
▪ The camera module is deactivated at an internal device temperature above 55°C / 131°F.
INFO
to avoid premature aging of the OLED display:
▪ If no key is pressed for 10 minutes, the OLED display is darkened.
▪ The OLED display is darkened from an internal device temperature of 60°C / 140°F.
▪ The OLED display is switched off from an internal device temperature of 75°C / 167°F.
Below these temperatures, the sighting can be used again or the OLED works with its full brightness.
Operation outside this temperature leads to incorrect measurements and may damage the device.
To comply with the permitted ambient temperature, sufficient distance from the (hot) measuring object is to ob-
serve. With radiant heat from the front, the pyrometer can be protected by a cooling plate, the use of the py-
rometer in ambient temperatures outside the permissible pyrometer ambient temperature is possible with an
additional cooling housing (accessory).
▪ The internal device temperature can be read out in the connection area
or in the control window
▪ It is possible to configure one of the switching outputs so that a corre-
sponding signal is switched when the maximum temperature is ex-
ceeded (see 4.1.4
Configurable Inputs /
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 radia-
tion 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 fo-
cus point of the optics (focus distance) the spot size
diameter is the smallest. Also measurements in the de-
focused area can be done to determine the average
temperature of a bigger spot.
To get a correct measurement result, the following re-
quirements must be observed:
▪ For measurements through window, the window ma-
terial has to be observed. If the transmission proper-
ties are not uniform (e.g. quartz glass), the corresponding emissivity slope has to be entered.
▪ A viewing window between pyrometer and the measured object must have constant transmission properties
in the spectral range of the pyrometer (e.g. quartz glass or BK7 crown glass).
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of the SensorTools software.
Configurable Inputs / Outputs and under
Outputs).
METIS M311 / M322 / H311 / H322 (12-pin device connector)
→
7.1.5
6.2.1
Focus point
DT: internal de-
vice temperature
via software
Emissivity slope).
Spot size bigger