AN4626
Application note
VL6180X distance measurements versus -30 / +85°C extended
temperature range
Introduction
The VL6180X module combines a proximity sensor based on ST’s patented FlightSense™
technology and an ambient light sensor in one package. The VL6180X interfaces to your
micro-controller via the industry standard I2C bus.
This application note describes how VL6180X performs distance measurements versus a
temperature range from -30°C to +85°C.
Figure 1. VL6180X module
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Set up
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Set up
All distance measurements are done with below conditions
•
•
VDD = 2.8V (device supply voltage)
Luminance = 0 lux
Figure 2
to
Figure 5
give typical distance measurements on different color targets.
For the purposes of this document all targets are referred to in terms of their photopic
(visible spectrum) reflectance. It should be noted that the photopic reflectance of a target is
not necessarily the same as the reflectance at 850nm (the wavelength of the VL6180X
emitter). Unless otherwise specified, all targets referenced in VL6180X documentation are
Munsell neutral color (gray) charts from X-rite (www.xrite.com), filling the entire field of view.
The Munsell notation and reflectance is listed here for each target used.
•
•
•
•
Note:
N2.00/M 3% ‘Black’
N2.75/M 5% ‘Black’
N4.75/M 17% ‘Gray’
N9.50/M 88% ‘White’
/M refers to a mat finish on the target
Measurements
Figure 2. Measurements on a white target (88% reflectance)
88% reflectance
110
100
90
80
Measurement in mm
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
110
Distance in mm
85°C
70°C
60°C
23°C
-10°C
-20°C
-30°C
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Measurements
Figure 3. Measurement on a gray target (17% reflectance)
17% reflectance
110
100
90
80
Measurement in mm
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
110
Distance in mm
85°C
70°C
60°C
23°C
-10°C
-20°C
-30°C
Figure 4. Measurement on a black target (5% reflectance)
5% reflectance
110
100
90
80
Measurement in mm
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
110
Distance in mm
85°C
70°C
60°C
23°C
-10°C
-20°C
-30°C
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Conclusion
Figure 5. Measurement on a black target (3% reflectance)
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3% reflectance
110
100
90
80
Measurement in mm
70
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
90
100
110
Distance in mm
85°C
70°C
60°C
23°C
-10°C
-20°C
-30°C
Conclusion
Over the temperature range -30°C to +85°C, VL6180X reports a distance measurement
varying linearly with the temperature and with a constant offset.
In a system submitted to a large variation of temperature and having the temperature
information, the VL6180X behavior allows the user to develop a simple algorithm to
compensate this offset in temperature..
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Revision history
1
Revision history
Table 1. Document revision history
Date
28-Nov-2014
Revision
1
Initial release.
Changes
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