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
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
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.
The shortest exposure to ultraviolet radiation that produces
reddening of the skin within 1 to 6 hr and disappears in 24
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
Relationship between µW/cm² and MED/hr: 1 [MED/Hr] = 5.83
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
"ISO/CIE 17166:2019(en) Erythema reference action spectrum and standard erythema dose".
Available for purchase. Extract
This standard replaces
"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:
available for purchase).