UV-meters
Introduction
The requirement for XP applications is to measure very low levels of
UV.
Most of the sensors on the market are for high levels (for warning of
getting a sunburn on normal skin), and so cannot be
used.
Prototype of commercial UV-meter made in collaboration with Enfants de
la Lune*
Functional specification (December 2018)
- Sensor: unfiltered SiC photodiode from sglux or TOCON version of unfiltered SiC photodiode with integrated amplifier.
- Display on top of the meter.
- Press-and-hold power button (on top of the meter) to make a measurement. Releasing the power button fully switches off the device.
- Reading of 00 mMED/hr up to 199 mMED/hr (disabling the rightmost
digit of a 3½ digit display).
- Internal precision in 0.1 mMED/hr.
- For calibration the digit on the right can be enabled, allowing the internal precision of 0.1 mMED/hr to be shown.
- Reading should be stable within two seconds.
Calibration
- Enable the rightmost digit, allowing the internal precision of 0.1 mMED/hr to be shown.
- Calibrate against a calibrated CIE 1987 erythema weighted instrument
with a source spectrum of natural unfiltered sunlight.
- Any value between 50.0 mMED/hr and 199.9 mMED/hr may be used to
calibrate.
- Difference between the two meters may be ± 0.3 mMED/hr.
- Verify with no light on the sensor a reading of 00.0, ± 0.3 mMED/hr.
- Any value between 50.0 mMED/hr and 199.9 mMED/hr may be used to
calibrate.
- Disable the digit on the right with an internal switch or jumper.
Technical implementation suggestions
- Handheld box: Serpac M6.
- Enable the rightmost digit with an internal switch or jumper that can be reachable via the battery trap.
- Power supply by a single 9V battery.
Original User Requirements (Summer 2016)
The following requirements were agreed on in the Summer camp 2016:
- Reading like .000 MED/hr (like the existing meter)
- Internal precision in .0001 MED/hr (so that all three digits that are shown are precise)
- Calibration precision on .0001 MED/hr internal precision level
- Display on the meter itself (not needing a smartphone for display).
- Allows easy use, less likely that battery is empty (reduces risk taking).
- No need for continuous measurement or logging.
Alternative acceptable implementation:
- Readings like 00 mMED/hr, up to 99 mMED/hr (disabling the rightmost
digit of a 3½ digit display), possibly up to 199 mMED/hr.
For calibration the digit on the right can be enabled, allowing the internal precision of 0.1 mMED/hr to be shown.
Features to make it the perfect product:
- Possibility to show reading in .0001 MED/hr level (may be shown as 00.1 mMED/hr) for calibration and specialist use by internal switch or any other way, no need to be able to switch easily
- A happy smiley showing in the display when reading is .000 (don't care about the non visible digit) This would require a large volume of custom displays to be purchased.
- If a smiley is not possible two LEDs that show OK (green), or non OK (red) (a single LED may bring confusion for red/green colour blind people).
Background information about the required resolution:
Currently (2016) the French Enfants de la Lune association is using an
erythema-weighted meter calibrated in MED/hr, which is used as a survey
meter to determine the safety or otherwise of an environment.
The instrument display has a precision of 1 mMED/hr. If it does not read
zero (i.e., if the dose rate is greater than about 0.5 mMED/hr) they
consider it unacceptable to go out unprotected.
Now it is clearly questionable what dose is clinically relevant, but as
this intensity level is reasonably achievable with window film and
adapted lighting etc., they have basically set their limit at the
minimum detection level of their instrument. So this is where our
instantaneous sensitivity requirement comes from.
Handheld UV meters - commercially available
-
Solarmeter (a division of Solar light
Co)
-
Model 5.7 UV meter
(demonstrated)
- Resolution 1 µW/cm²
- Irradiation range 0-1999 µW/cm² Total UV
- Seems too sensitive for UVA light (320nm-400nm) so can only be used as relative measurement with sunlight.
- Uses a Hamamatsu 5842 GaAsP photodiode - End of life (Jan.2019)
- Note on Solarmeter Model 5.7 and details about required wavelengths (in French)
- See [4]: Analysis of Compact Fluorescent Lights for Use by Patients with Photosensitive Conditions, Rachel S. Klein, 2008. (using Solarmeter Model 5.7)
-
Model 7.0 UV meter (MED/HR ERYTHEMALLY Effective (Eeff) UVR)- The Model 7.0 has a resolution of 0.1 MED/hr whereas we need 0.001 or preferably better.
-
Model 5.7 UV meter
(demonstrated)
-
- Model 3D-XP
- Also available as the UV MINDER Model 3D-XP Xeroderma Erythemal UV Intensity Meter for measuring very low UV intensity to 3 decimal places
- Readout range: 0...19.99 MED/Hr (standard model). The Xeroderma Erythemal UV Intensity Meter has one more decimal place (0...19.999 MED/Hr).
-
There is no datasheet of the Xeroderma Erythemal UV Intensity
Meter model
- It is this model that is used as reference. It has only one detector, mounted in the middle of the device.
-
-
Portable UV Radiometer (MG-07.1S) - GUVI-T11S7-LA9
- Uses external sensor
- No display in mMED/hr
- No experience with this device in XP community (0 offset, showing 0 behind UV protected windows?)
-
Portable UV Radiometer (MG-07.1S) - GUVI-T11S7-LA9
See also
Radiometer
Units
- Minimal Erythemal Doses per Hour (MED/Hr)
- The shortest exposure to ultraviolet radiation that produces
reddening of the skin within 1 to 6 hr and disappears in 24
hr.
The minimal erythemal dose is used to calculate the duration of therapeutic exposure to ultraviolet light. For treatment using a “hot” ultraviolet lamp (UV-A or UV-B), the dose is calculated at a distance of 30 in. The minimal erythemal dose for “cold” ultraviolet (UV-C) is standardized at 30 to 38 sec at a distance of 1 in. Synonym: erythema dose; threshold dose (from thefreedictionary.com)
- The shortest exposure to ultraviolet radiation that produces
reddening of the skin within 1 to 6 hr and disappears in 24
hr.
- Relationship between µW/cm² and MED/hr: 1 [MED/Hr] = 5.83
[μW/cm2]
- based on [6] (from Solarlight: Sensors - Biologically Weighted UV-B Detector PMA2101).
- 1 UVI: standard mid-day solar radiance in Nothern hemisphere (Canada?) (weighted with the Erythemal action spectrum), and then divided by 10.
- 1 UVI = 2.5 µW/cm²
- 1 UVI = 25 mW/m²
- 1 MED: that dose of UVR required to produce a barely perceptible erythema in people with skin type 1 (200 Jm-2 of biologically effective UVR) [5].
- 1 MED corresponds to the UV dose necessary to get a light sunburn in 20 minutes, on light skin, e.g. 21 mJ/cm2 at 297 nm radiation.
- 1 MED/hr = 5.8 µW/cm²
- 1 MED/hr = 2.32 UVI
- 1 SED = 0.01J/cm²
- 1 SED/hr = 2.78 µW/cm²
- 1 SED/hr = 1.11 UVI
See also
-
Solarlight: Sensors - Biologically Weighted UV-B Detector
PMA2101
- Gives quite some info about the wavelengths, MED/hr and has also some graph about when DNA breaks. Also scientific references.
Sensitivity wavelength range for XP
In April 2018 we have received mails from medical doctors explaining that the required detection range for XP is from 290 to 380 nm. For wavelengths above 380 nm XP patients are as sensitive as others as the repair is not related to "NER" (Nucleotide Excision Repair):
"Il faut se rappeler que les patients XP sont essentiellement déficients dans la réparation des dimeres de Py et des Py6/4Py qui sont essentiellement faits dans les UVB et les UVA jusque à 360-380nm. Après il existe aussi des lésions sur l'ADN mais pour lesquelles les XP sont aussi performants que les autres car leur réparation n est pas liée au NER."
See also
Standards
- "International Standard ISO 17166:1999(E)—CIE 007, E:1998, Erythema Reference Action Spectrum and Standard Erythema Dose", International Commission on Illumination (CIE) (1999), 1st edn., International Organization for Standardization (ISO), Geneva, Switzerland. (ISO: extract, available for purchase).
Calibration methods
- NIST standard (reference needed)
Articles
[1] McKinlay A.F. and B.L. Diffey, “A reference action spectrum for
ultraviolet induced erythema in human skin”, CIE Journal, 6, 17-22,
1987
[2] Morys M., D. Berger, “Accurate measurements of biologically
effective ultraviolet radiation” SPIE Proc. 2049, pp. 152-161, 1993.
[3] Parrish J.A., K.F.Jaenicke, R.R. Anderson ”Erythema and
melanogenesis action spectra of normal human skin” Photochem. Photobiol.
36, pp. 87-191 (1982)
[4] Analysis of Compact Fluorescent Lights for Use by Patients with
Photosensitive Conditions,
Rachel S. Klein, 2008. (using Solarmeter Model 5.7)
[5] Solar Ultraviolet Radiation - Global burden of disease from solar
ultraviolet
radiation,
World Health Organization, 2006
[6] Solarlight: Sensors - Biologically Weighted UV-B Detector
PMA2101
(2014) (Gives quite some info about the wavelengths, MED/hr and has also
some graph about when DNA breaks. Also scientific references.)
[7] Comparison of different UV sensors for use in an XP
radiometer, A. Butterworth,
December 16, 2018
[8] Indoor calibration method for UV index meters with a solar
simulator and a reference
spectroradiometer,
H. Zaini et al, Int. J. Metrol. Qual. Eng. 7, 101 (2016)
[9] Global Solar UV Index - A Practical
Guide, WHO
Ultraviolet radiation
[10] Development of a UV Index Sensor-Based Portable Measurement Device with the EUVB Ratio of Natural Light, Dae-Hwan Park, Seung-Taek Oh and Jae-Hyun Lim, Sensors 2019, 19(4), 754 (ESTS 2018 - Recent Advances and Developments in Sensor Technologies)
[11] Rationalizing nomenclature for UV doses and effects on humans, McKenzie et al, CIE 209:2014 and WMO-GAW Report No. 211 Joint Publication.
[12] Realization of a radiometric head for measurements of ultraviolet total erythemal effective irradiance, M.G.G Pelizzo, Applied Optics, 2007
See also
- Electronics (showing detector components)
1 July 2020