X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=doc%2Fmicropeak.txt;h=18a5afdf7b54673d756c0a51aee2ca447f472c32;hp=3621a2dcc17cffe23a7bb8a9999fafb1ea3c2d73;hb=HEAD;hpb=adf4bec88df1822031e1a8b00422de8b8b0c0cd4 diff --git a/doc/micropeak.txt b/doc/micropeak.txt index 3621a2dc..fb75aacb 100644 --- a/doc/micropeak.txt +++ b/doc/micropeak.txt @@ -1,15 +1,15 @@ = MicroPeak Owner's Manual Keith Packard ; Bdale Garbee -:revnumber: v1.9 -:revdate: 8 Oct 2018 -:copyright: Bdale Garbee and Keith Packard 2018 +:revnumber: v{version} +:revdate: 01 Jan 1970 +:copyright: Bdale Garbee and Keith Packard 2021 :stylesheet: am.css :linkcss: :toc: :doctype: book :numbered: -:pdf-stylesdir: . -:pdf-style: altusmetrum +:pdf-themesdir: . +:pdf-theme: altusmetrum :pdf-fontsdir: fonts include::header.adoc[] @@ -28,7 +28,7 @@ Keith Packard ; Bdale Garbee NAR #87103, TRA #12201 [verse] - Keith Packard, KD7SQG + Keith Packard, K7WQ NAR #88757, TRA #12200 == Using MicroPeak @@ -299,6 +299,43 @@ Keith Packard ; Bdale Garbee these applications, change in one application will affect the other. +== Protecting MicroPeak from Sunlight + + The MS5607 barometric sensor is sensitive to direct light. When light + shines through the holes in the cover to the components inside, the + reported pressure can vary wildly from the actual pressure. This + causes the reported altitude to have errors of thousands of + feet. + + MicroPeak should be installed in an opaque compartment in the airframe + and not subjected to sunlight. Alternatively, a small piece of + adhesive-backed open-cell foam can be attached to the device so that + it covers the barometric sensor and protects it from direct light. + + Here's what happens when MicroPeak is exposed to sunlight. At apogee, + I exposed MicroPeak to varying amounts of sunlight and you can see the + wild swings in altitude resulting from that: + + .MicroPeak in Sunlight + image::micropeak-flight-nofoam.png[width=430] + + You can carefully cutting a piece of adhesive-backed open-cell foam + and attach it to MicroPeak. It's important to press the adhesive to + the circuit board and not to the top of the barometric sensor or the + sensor may become blocked and not operate at all. Once you've attached + the foam, you should test MicroPeak on the ground to make sure it's + still working. + + .MicroPeak with Foam + image::micropeak-foam.jpg[width=430] + + That MicroPeak was in the same barometric chamber as the one which + generated the above results and the resulting flight data looks + correct: + + .MicroPeak in Sunlight with Foam + image::micropeak-flight-foam.png[width=430] + [appendix] == Handling Precautions @@ -327,10 +364,16 @@ Keith Packard ; Bdale Garbee sensor out of direct sunlight. The barometric sensor sampling ports must be able to - "breathe", both by not being covered by foam or tape or other - materials that might directly block the hole on the top of the - sensor, and also by having a suitable static vent to outside - air. + "breathe", both by not being covered by solid foam or tape or + other materials that might directly block the hole on the top + of the sensor, and also by having a suitable static vent to + outside air. + + One good solution is to use a small rectangle of Poron + 50-30031-12X12P or equivalent to cover the sensor. This is an + open cell foam in 1/32" thickness with an adhesive backing. It + seems to do a good job of blocking sun while still allowing + airflow to and from the sensor internals. As with all other rocketry electronics, Altus Metrum altimeters must be protected from exposure to corrosive motor