This Article is about:
- Minimum operating distance
- Optimal operating distance
- Examples of how an optimal operating distance can be defined
Minimum operating distance
As any optical device a thermal camera has a minimum distance at which it can be focused or at which it still can deliver an acceptable image.
For the cameras with a manual focus, the minimum operating distance is defined by the minimum distance, at which the camera can be focused.
For the cameras with focus-free optics, the minimum operating distance is the approximate distance, at which the image still looks sharp enough.
For Fluke cameras with the manual focus minimum operating distance is usually 15 cm.
For Fluke cameras with focus-free optics the minimum operating distance usually 45-50 cm.
Optimal operating distance
The optimal operating distance will depend on the size of the object you`d like to measure and the smallest details your camera can see which is given by its resolution (image size) and spatial resolution (IFOV).
For small objects like wires, when you use a camera with a low resolution and wide field of view, you need to be able to focus at distances closer on the object, or you could use a high resolution camera which will offer you the option to see a detailed picture from several meters away.
Examples, of how an optimal operating distance can be defined
A wire with cross-section of 1.5 mm2, typically used in residential and commercial electrical networks, has diameter with insulation of about 3 mm.
If you use the Ti401Pro or Ti480Pro, having IFOV of 0.93 mrad, to inspect the installation using this wire size, then maximum distance at which you will be able to "see" this wire, or distinguish details having the size compared to the wire diameter, will be:
3 mm / 0.93 mrad = 3.22 m ≈ 3 m
But to measure the temperature of this wire, you need to come closer to make sure, that the wire diameter is covered at least by the 3x3 pixels area on the thermal image. Which means, that you can measure this wire from the distance of 3 times closer:
3.22m / 3 = 1.07 m ≈ 1 m
If you apply the same approach for the TiS75+ or TiS55+, having IFOV of 1.91 mrad, then for the same installation, the maximum distance at which you will be able to "see" the wire, will be:
3 mm / 1.91 mrad ≈ 1.57 m
And to be able to measure the temperature of the wire, the distance at which you can try to do this should be not more than:
1.55 m / 3 ≈ 0.52 m
At the same time, if your installation uses wires with cross-section of 2.5 mm2, having outer diameter of 4 mm, for the same cameras you will get the following:
For the TiX401Pro / Ti480Pro
4 mm / 0.93 mrad ≈ 4.3 m to see
4.3 m / 3 ≈ 1.43 m to measure
For the TiS55+/TiS75+
4 mm / 1.91 ≈ 2.1 m to see
2.1 m / 3 ≈ 0.7 m to measure
You can use our online FOV calculator to define your camera optimal operating distance for your specific situation more precisely.