Datasheet

Designing the VEML6070 UV Light Sensor
Into Applications
Application Note
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Vishay Semiconductors
APPLICATION NOTE
Revision: 26-Mar-18
4
Document Number: 84310
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UVB rays - wavelengths ranging from 280 nm to 320 nm - are extremely energetic and harmful to the skin; they are responsible
for 65 % of skin tumors. Thankfully, only 0.1 % of the solar energy that arrives on the earth’s surface is in the form of UVB
radiation.
UVA rays - wavelengths ranging from 320 nm to 400 nm - are less powerful than UVB rays, but are highly penetrating. They are
capable of reaching the skin and are responsible for photoaging and the onset of different forms of skin cancer. 4.9 % of solar
energy is made up of UVA rays.
In order to estimate the energy behind UV radiation and the risk level associated with it, the UV-index was established.
It is a quite complex calculation, weighted according to a curve and integrated over the whole spectrum. So, it cannot simply
be related to the irradiance (measured in W/m
2
).
The calculated index value appears on a scale of 0 to ≥ 11. This index scale is linear and its relation to irradiance strength is
shown below.
Fig. 6 - Strength of Irradiance and the UV-Index
In order to estimate the energy behind UV radiation and the risk level associated with it, the VEML6070 simply reads out the
irradiance value and compares it with pre-defined values.
These given values are estimated, taking care to weigh the irradiance strength according to the wavelength and response
performance of the VEML6070 (fig. 3).
Setting up and programming the VEML6070 is easily handled with just three I
2
C-bus addresses: 0x70, 0x71, and 0x73.
TABLE 1 - VEML6070 SLAVE ADDRESS AND FUNCTION DESCRIPTION
SLAVE ADDRESS OPERATION
0x70 Write command to VEML6070
0x72 Reserved
0x71 Read LSB 8 bits of VEML6070 ultraviolet light data
0x73 Read MSB 8 bits of VEML6070 ultraviolet light data
Low
Moderate
High
Extreme
Very High
Strength of Irradiance
0.3
E
e
(W/m
2
)UV-Index
0.0
0.2
0.1
12
0
9
8
7
6
5
4
3
2
1
10
11