Applications Guide
146
Modline 5
• Track and Hold temperature readings are affected by the Response Time setting.
Figure 85: Track and Hold
Example: you may want to scan the surface of a moving workpiece and hold the temperature reading
at middle point on the workpiece, while ignoring the readings at the beginning and the end of the
workpiece.
Another Example: the temperature tracking can be made to hold a temperature even after the
temperature in the sighted area has dropped. It will hold the value without any decay until the switch
is opened.
8.8
Avoiding Common Measurement Problems
8.8.1
Viewing Angle Limitations
Acute viewing angles can present the problem of reduced emissivity values, particularly if you are
dealing with smooth target surfaces.
shows the permissible angles (for all Sensor Series) when viewing smooth surfaced objects
such as metals, glass or plastics. Angles up to 45° from the perpendicular usually will not appreciably
affect the measurement, although the smaller the angle from the perpendicular the better. In general,
angles greater than 45° should be avoided. An increase in reflectance occurs when smooth surfaces are
viewed at large angles, and consequently the target emissivity decreases.
8.8.2
Background Interference
Under ideal circumstances, the radiant energy being measured should be from the target only. This is
why you must center the Cone of Vision on the target and make sure that its cross-section (spot size) is
smaller than the target. That way the sensor can't "see" past the target into the background. Although
Peak Picker and Track and Hold Signal conditioning cannot be simultaneously
selected. Use of Peak Picker with zero or very low Decay rates and an external reset can
accomplish similar results.
Sensor Output
Target Temperature
Hold
Track
Time
Signal
