= MicroPeak Owner's Manual
Keith Packard <keithp@keithp.com>; Bdale Garbee <bdale@gag.com>
-: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 2020
:stylesheet: am.css
:linkcss:
:toc:
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
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