DE9321199U1 - Personal UV dosimeter - Google Patents

Description

personal üV dosimeter
Description

The personal UV meter measures the irradiance using an integral measuring method. The irradiance is evaluated according to the relative spectral effect function defined by the GIE (Commission Internationale d' Eclairage) for UV erythema for the human body. Both natural solar radiation and artificial UV radiation sources are possible sources of radiation.

Figure 1 shows the overview scheme and Figure 2 shows a circuit diagram for an example solution.

The sensor (1) is an optoelectronic receiver based on silicon carbide without a diffuser and without an optical filter. The relative spectral sensitivity of the sensor (silicon carbide chip) and the influence of the optical properties of the housing (synthetic resin) is shown in Figure 3. The electrical signal of the UV sensor (1) is amplified by the operational amplifier (2) and fed to an analog input of a single-chip microprocessor (3) or a circuit arrangement with the same functionality (microprocessor and A/D converter). The irradiance is shown on the display (4) after the signal has been processed by the microprocessor.

(3) taking into account the radiation spectrum of the UV source.

When limit values recorded or calculated by the microprocessor are reached, an acoustic signal can be emitted on the signal generator (5). The keyboard (6) is used to select the display functions and the processing algorithms. A real-time clock is implemented in the microcomputer. By calculating the product of the irradiance and irradiation duration, the dose (photobiologically effective irradiation) is determined in the microprocessor (3) and shown on the display.

(4) is displayed.

From the measured and assessed erythematous irradiance of the global radiation or an artificial UV radiation source, the length of stay and the value of the minimum erythematous dose (MED) for the human body [2], the permissible length of stay (forecast value) is determined and displayed, and the remaining time is calculated and displayed. The remaining time is updated depending on the intensity over the entire measurement time. If the display value of the remaining time reaches the value 0, the signal generator

(5) an acoustic warning signal is issued to stop the irradiation. The following are taken into account in the calculation:

- MED values related to at least 4 skin types [1]

- a correction of these values depending on the values entered for the individual sensitivity to UV radiation and

- the degree of pre-tanning.

The calculation includes the separately entered but also mathematically linked sun protection factors of a sunscreen used (SPF according to DIN 67501 and SPF according to US standard).

A monitor, an LED, LCD or fluorescent dot matrix or character display can be used as the display (4) (example in Figure 2).

The measurement of the irradiance is characterized by the fact that when the device is positioned without shading the sensor, the device does not have to track the sun, since the sensor has an opening angle of more than 150°. The spectral sensitivity of the sensor is not dependent on the angle of incidence of the light, since the sensor is used without additional UV pass filters (interference filters). By suitably adjusting the amplification of the operational amplifier (2), the sensitivity of the sensor (1) and the absence of filter-related attenuation, an optically active sensor surface of significantly less than 0.01 mm ¹ ' is used.
Sensor and the absence of interference filters and diffusers enable cost-effective solutions for large opening angles.
Since all interference filters have in common that the wavelength of the greatest transmission depends on the angle of incidence of the radiation, such arrangements must be interspersed with telecentric beam paths (parallel bundles) or at least bundles with a small opening angle. This fact calls into question the fundamental functionality of previous solutions of UV dosimeters with interference filters for use as personal measuring devices without precise tracking of the device with respect to the radiation source. In addition, scattered radiation is not recorded or is recorded very incorrectly in previous solutions. The arrangement presented eliminates both disadvantages. ^: -

Relevant state of the art ;

radio television electronics 41 (1992) 8 p. 565 f

[1] DIN5050

[2] UV radiation loose-leaf collection Professional Association for Radiation Protection
eV
FS-9259/3-AKNIR, Sept. 1992

[3] Protection of humans from solar radiation and from use
of UV irradiation devices. Recommendation of the Radiation Protection Commission,
Federal Republic of Germany, Federal Gazette 144-90

Patent documents cited as state of the art ;

EN 3429541 535, 244 US 4, 710, 115 US 3, 917, 948 US 3, 428, 050 US 4,

Claims (2)

Protection claims 1. Device for measuring the irradiance, for determining the dose, the permissible duration of stay and for warning against exceeding the permissible individual dose of a person * under solar radiation and artificial UV sources i... _I . characterized, that a UV radiation sensitive sensor (silicon carbide) (1) is connected without a UV transmission filter via a · .**» thermally and drift compensated amplifier (2) to ai _t »;« ₍ microprocessor (3) to which a ** device (6) for entering individual values, a display device (4) and a signal generator (5) are also connected. * 2. Device according to claim 1, characterized in that in order to achieve a particularly large opening angle, the housing of the UV radiation-sensitive sensor (1) is mechanically designed in such a way that the chip surface is positioned as close as possible to the housing surface outside the focal point and within the simple focal length in the housing. See picture 1