LumaSense Technologies M67 - Manual (Page 13)

M67, M67S Manual
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6. Pre-installation guide
This section describes briefly, various concepts, which govern the successful application of the INFRADUCER. It is
worthwhile studying this section carefully to ensure that you will obtain the most accurate readings from the instrument.
6.1 Focus
To ensure that the radiation received by the INFRADUCER comes from the desired target and nowhere else, an optical
focusing system has been employed in the design. This system allows thermal radiation from a fixed location in front of the
INFRADUCER to be focused exactly on the infrared detector located within. This is very similar to the way a photographic
camera focuses a scene onto a photo sensitive Film.
The M67 is pre-focused at the factory to the distance specified on its specification label. The M67S provides through the lens
sighting which enables the user to focus on the object and to observe the field of view through the view finder. The M67S is
offered in three focus ranges, (see section 5, page 10).
The target area "seen" by the INFRADUCER has a fixed diameter (usually about 1 inch or 25mm) at the predetermined
distance where the target is located. The target must be larger than this minimum area.
It is important to stress that the INFRADUCER may also be used at distances other than the one stated in the specifications. An
explanation follows under section 6.2, page 12.
6.2 Field of view
In infrared thermometry, field of view is defined as the minimum target diameter, which either partially or completely
eliminates the influence of background radiation. The F.O.V. is expressed as a distance to size ratio. For example, if the F.O.V.
for a INFRADUCER were 15:1, then this would mean that the instrument would “see” a spot of 1 inch/(25mm diameter) 15
inch (38cm) from the Lens.
FOV
e c n a t s i d s u c o f
e z i s t e g r a t

Example: M67 FOV = 30:1
focus distance = 15 
target size = 15 / 30 = 0.5 
The reticle in the M67S defines the field of view. When sharply focused, accurate readings will be obtained if the object is
equal to or larger than the reticle.
An important principle, which must be understood, is that, it is possible to use the INFRADUCER at distances other than the
field of view specification distance. This is possible provided that the new minimum target diameter is also taken into account.
Figure 6 shows graphically and algebraically how other distance/minimum target diameter combinations can be determined. An
explanation follows.
Line L is the diameter of the opening at the front of the INFRADUCER housing (lens diameter). Line d is located at a distance
F equal to the focus distance specification and is equal in length to the minimum target diameter (perpendicular to the control
axis of the instrument). Dotted line DB and solid line BC are on the same straight line. Similarly, AE extends into EF. The
INFRADUCER can be used at any distance less than x or greater than x provided the target diameter is greater than the space
that lies (perpendicular to the axis) between solid lines ABC and DEF.
This principle has important practical applications in cases when the INFRADUCER must view targets located behind obstacles
and the available clearance is smaller than the target. An example is shown in Figure 5. Here, the INFRADUCER is being used
to measure the temperature of a target located behind closely spaced induction heating coils.
Another important principle to understand is that the target need not necessarily be perpendicular the axis of the
INFRADUCER. As long as the target size is such that the area viewed is greater than that which falls within the solid lines ABC
and DEF (Figure 6), an angular orientation with respect to the axis is permissible.