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## Introduction
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This is a simple design for a handheld wideband UV-meter.
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It uses as much as possible ready-made components and will need a
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minimum amount of soldering.
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It fully complies to the requirements, but will only need a sticker over
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the rightmost digit to show in mMED/hr.
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[LUVI](https://www.ohwr.org/project/luvi/wikis/) is a simple design for a handheld UV-meter with an Erythema sensitivity curve. It uses as much as possible ready-made components and will need a minimum amount of soldering.
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Early ideas on how to design the LUVI UV-meter that may be helpful to see the design choices that have been made and the different issues that have been looked at when making the design, are described at
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* [Early design ideas](https://www.ohwr.org/project/uv-mask/wikis/uv-meter-design-ideas)
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## Components
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... | ... | @@ -17,43 +16,14 @@ the rightmost digit to show in mMED/hr. |
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- 117.5 mm x 72.5 mm x 25.5 mm
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- Integrated 9V battery compartment with clip
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- Silicon rubber boot as option
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- [CHH451PBK Textured lid](https://www.camdenboss.com/camden-boss/chh451pbk-45-series-enclosure/c-23/p-17800) - [Farnell](https://fr.farnell.com/camdenboss/chh451pbk/boitier-taille-1-pp3-bat-noir/dp/1894784)
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- [CHH456PBK Recessed lid (for a label)](https://www.camdenboss.com/camden-boss/chh456pbk-45-series-enclosure/c-23/p-17815) - [Farnell](https://fr.farnell.com/camdenboss/chh456pbk/boitier-taille-1-pp3-noir/dp/1894790)
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- [CHH451BBK - 45 Series rubber boot, Size 1, Black](https://www.camdenboss.com/camden-boss/chh451bbk-45-series-rubber-boot/c-23/p-17796)
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- [CHH451BBL - 45 Series rubber boot, Size 1, Blue](https://www.camdenboss.com/camden-boss/chh451bbl-45-series-rubber-boot/c-23/p-17797) - [Farnell](https://fr.farnell.com/camdenboss/chh451bbl/boitier-taille-1-bleu/dp/1894797)
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- [62 Series](https://www.camdenboss.com/camden-boss/enclosures/plastic-enclosures/handheld-cases/ergonomic-keyfobs-(62-series)/c-23/c-2031) - not baseline, interesting for miniaturisation
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- **70 mm x 50 mm x 20 mm**
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- [CHH623BLK](https://www.camdenboss.com/camden-boss/chh623blk-62-series-enclosure/c-23/p-17826) - [Farnell](https://fr.farnell.com/camdenboss/chh623blk/boitier-abs-noir-70x50x20mm/dp/2346721)
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- Serpac [M6](http://www.serpac.com/m6.aspx)
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- **105.41 mm x 60.96 mm x 21.59 mm**
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- Integrated 9V battery compartment with contacts
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- Can be customised with [full colour
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printing](http://www.serpac.com/printing.aspx)
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- [Arrow](https://www.arrow.com/en/products/m6bk/serpac-electronic-enclosures)
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(black)
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- [Mouser](https://www.mouser.ch/Search/Refine.aspx?Keyword=serpac+m6)
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(all)
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([black](https://www.mouser.ch/ProductDetail/SERPAC/M-6-B?qs=%2fha2pyFaduhxVtpfGjyF0ov2qd89EDKxcsrqNOoDIOYUQeg5GG3igQ%3d%3d))
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- [BOPLA](https://www.bopla.de/en.html)
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- [BOS 400 with compartment for 9V
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battery](https://www.bopla.de/en/enclosure-technology/product/bos/bos-400-400-asc-401-401-asc-enclosures/bos-400.html)
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- 100 mm x 65 mm x 24 mm
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- Alternatively [BOS 500
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series](https://www.bopla.de/en/enclosure-technology/product/bos/bos-500-501-502-503-enclosures.html)
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(120 mm x 60 x 25 mm)
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- [RS
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BOS502](https://fr.rs-online.com/web/p/portatifs/0581638/)
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(attention, 502 has area for display, should use 503).
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Design
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- Cutouts for display, pushbutton, sensor, hole for calibration
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- Printed customisation by factory or with sticker
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- Cutouts for display, pushbutton, sensor
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- Printed customisation by factory
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-----
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... | ... | @@ -63,7 +33,8 @@ Design |
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DMS-20lcd-1-5-c](https://www.murata-ps.com/datasheet?/data/meters/20lcd.pdf)
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- 2V full range, auto-zero
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- Full-scale fine calibration with screwdriver (only ±50 counts or
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±2.5%)
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±2.5%) - *not functional nor accessible on the LUVI design.*
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- Battery low indicator turns on at 3.7V
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- [Arrow](https://www.arrow.com/en/products/dms-20lcd-1-5-c/murata-power-solutions)
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- [Farnell](https://fr.farnell.com/search?st=DMS-20LCD-1-5-C)
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- [DMS Application note 3: Analog Common and Reference
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... | ... | @@ -80,49 +51,13 @@ Design |
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### UV-sensor
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- sglux [SiC UV TOCONs / Broadband UV
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sensor](https://sglux.de/en/product-category/sic-uv-tocons/broadband-tocons/)
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- [TOCON\_ABC5](https://sglux.de/en/product/tocon_abc5-en/)
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- sglux [SiC UV TOCONs / UV-Index (Erythema)](https://sglux.de/en/product-category/sic-uv-tocons/broadband-tocons/)
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- [TOCON\_E2](https://sglux.de/en/produkt/tocon_e2-en/)
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- Gives 0-5V output
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- "Scatter" (tolerance) of ±20%. Should be able to calibrate this
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out.
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- See [sglux FAQ](https://sglux.de/en/faq): *What about the
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TOCON scatter?*
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- Lower and higher sensitive sensors exist
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##### Calculation of required sensitivity and sensor
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- We want 0.2 MED/hr at 2V output = 0.5 MED/hr at full scale 5V
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output.
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- Scaling factor is 0.24 MED/hr/W/m² so we want 0.5/0.24 = 2.08 W/m²
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full scale
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- Correction factor of 0.24 for a wideband TOCON ABC (that is more
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sensitive for UVA) to correct so that under natural sunlight
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gives same reading in med/hr as a perfect erythema meter.
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- See [*Comparison of different UV sensors for use in an XP
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radiometer*](https://www.ohwr.org/project/uv-mask/wikis/Documents/Comparison-of-dierent-UV-sensors), A.
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Butterworth, December 16, 2018 (paragraph above Table 1).
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- 2.08 W/m² = 2.08e-4 W/cm² = 208 µW/cm²
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- The closest is ABC5 with 180 µW/cm² full scale.
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- 0.2 MED/hr would then give an output of 0.2/0.24 \* 1e-4/180e-6
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\* 5 = 2.3 V.
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- The tolerance of the TOCONs is ±20%, some of them may not give
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us the required output: 2.3V\*0.8= 1.84V instead of 2.000V.
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Should take this in account that 1.84V can be calibrated to read
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as 2.00V. 2.3V\*1.2=2.76V. So calibration range must be 1.8V -
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2.8V.
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- For comparison 0.2 MED/hr should give 0.79 V on the TOCON E1.
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Calibration range 0.6V - 1V.
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- Assuming the powers that are quoted by sglux are in W/cm² are
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normalised to the sensitivity spectrum of the sensor.
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Likely not needed: digital calibration could be made with a [TOCON
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Adjustment board](https://sglux.de/en/product/tocon-adjustment-board/)
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(needs specific box to make setting).
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Note that dependent on the design, the battery low indicator could not work (it turns on at 3.7V), or too late when the battery is almost empty. Vref would lower first, showing higher values than the actual one. This is a safe behaviour.
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Also, after roughly 6.5V a battery seems quickly to go to 0V. Until 6.7V we can have Vref still at 5.000V
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- "Scatter" (tolerance) of ±20%.
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- See [sglux FAQ](https://sglux.de/en/faq): *What about the TOCON scatter?*
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- Higher sensitive sensors exist and is used in specialist version
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- [TOCON\_E1](https://sglux.de/en/produkt/tocon_e1-en/)
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-----
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... | ... | @@ -130,37 +65,21 @@ Also, after roughly 6.5V a battery seems quickly to go to 0V. Until 6.7V we can |
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### Printed Circuit Board
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- Holds
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- TOCON
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- Needs to be mounted at 90 degrees as on front-side of box.
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- Needs an additional board?
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- Ask sglux if TOCON can come with wires or a low-cost
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connector allowing assembly at 90 degrees
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- Push button (height should be right)
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- Wires up to 9V holder
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- TOCON mounted on a separate PCB to allow a 90 degrees angle to have opening at the front-side of box
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- Diode for protection of battery reversal
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- Ultra-stable 5 Volt reference voltage IC that powers all components
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- Display/voltmeter
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- Needs careful adjustment in height, or with socket that
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allows movement? Or wire the display up to the PCB?
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- Allow for hole in PCB to reach calibration screw
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- Resistors for the full-scale adaptation from 0-5V to 0-2V (1%
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metal-film). Can be done with Vref.
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- Tolerance of TOCON ±20%. Should be able to handle this. Can
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be done with Vref. 1.8V should be able to read as 2.0V.
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- Use high-precision potentiometer?
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- Use selectable resistors?
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- Use a digital potentiometer or sglux setting
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board/schematics (requires programming with special box
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and connector)
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- Final fine (±50 counts or ±2.5%) calibration on
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Display/Voltmeter
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- Needs careful adjustment in height when soldering. 3D-printed template for assembly is designed.
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- Resistors and multi-turn potentiometer for the full-scale adaptation and calibration
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- Resistors and multi-turn potentiometer for the zero-reading calibration
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- Connector for pushbutton
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- Wires to the 9V battery clip
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-----
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### Various
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- 9V battery
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- Assembly: mask off the rightmost digit with tape or a dedicated
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sticker. Or possibly not even needed as no UV will read as 000
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anyway.
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---
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... | ... | @@ -177,4 +96,4 @@ Also, after roughly 6.5V a battery seems quickly to go to 0V. Until 6.7V we can |
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-----
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Erik van der Bij - 10 October 2019 |
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Erik van der Bij - 28 November 2019 |