From: Keith Packard Date: Mon, 17 Jun 2019 21:47:56 +0000 (-0700) Subject: doc: Describe what sunlight does to MicroPeak and how to protect it X-Git-Tag: 1.9.1~1^2~84 X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=0a466e9869633c6ce7e43ff24ba2afff938461dd doc: Describe what sunlight does to MicroPeak and how to protect it Show flight data from micropeak in sunlight, a picture of foam installed on micropeak and the resulting data. Signed-off-by: Keith Packard --- diff --git a/doc/micropeak-flight-foam.png b/doc/micropeak-flight-foam.png new file mode 100644 index 00000000..c7d37e37 Binary files /dev/null and b/doc/micropeak-flight-foam.png differ diff --git a/doc/micropeak-flight-nofoam.png b/doc/micropeak-flight-nofoam.png new file mode 100644 index 00000000..ecf83f7b Binary files /dev/null and b/doc/micropeak-flight-nofoam.png differ diff --git a/doc/micropeak-foam.jpg b/doc/micropeak-foam.jpg new file mode 100644 index 00000000..73a40400 Binary files /dev/null and b/doc/micropeak-foam.jpg differ diff --git a/doc/micropeak.txt b/doc/micropeak.txt index b6dd0ddb..f1feeec4 100644 --- a/doc/micropeak.txt +++ b/doc/micropeak.txt @@ -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 as much as 3000-4000 + 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