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# Member #151132

Member Since: September 14, 2010

Country: United States

• If you want to maximize the voltage difference between the 16 possible levels obtained using the technique shown in the weather meter datasheet, the optimum resistor value for the resistor you supply for the voltage divider appears to be about 3511 Ohms, rather than the 10k resistor value shown in the Weather Meter datasheet as an example.

With the 10k resistor, and a 5V power supply, the minimum difference between voltage values obtained is about 45.4 mV. Using a 3511 Ohm resistor and the same 5V power supply, you can achieve a minimum difference of about 96 mV. You can do almost as well with a more-common 3600 Ohm resistor, which yields a minimum voltage difference of about 95 mV, again assuming a 5V power supply.

Thus sayeth Excel.

• There are two different datasheets for the weather gauge product on the Sparkfun site. This article links to https://www.sparkfun.com/datasheets/Sensors/Weather/Weather%20Sensor%20Assembly..pdf?_ga=2.14578160.633493603.1572019408-434657447.1570326130 .

As the voltage output will depend on the value of the external resistor used, there is not one common conversion function. For an example of how to calculate this, please reference the datasheet for the meters.

This datasheet contains at least one error, in the voltage for 315 degrees, which should be 4.33V, not 4.78V.

The link to this datasheet also appears at the bottom of the hookup guide.

The updated datasheet contains the correct voltage value for 315 degrees.

I haven't compared the two datasheets looking for other errors. Caveat emptor.

• Please update the datasheet or link thereto. The current link points to a preliminary data brief. Mouser links to a datasheet at http://www.mouser.com/ds/2/389/DM00112632-490369.pdf .

• 433011, did you get this working? I'm interested in doing the same thing in my Bixler, where I have my APM 2.5 mounted too near some power wiring.

• The link above for the Expansion Board, http://store.diydrones.com/ProductDetails.asp?ProductCode=KT-0001-01 , doesn't work.

Ditto on the link for the X, Y, and Z sensors, http://store.diydrones.com/ProductDetails.asp?ProductCode=SE-0002-01 .

• I'm having a bit of trouble reconciling the "bandwidth" (frequency response?) spec on this thing with the chart in the data sheet, which seems to show a pretty flat response from around 50 Hz through 1 kHz. I can see why you'd need a pretty good LPF between this thing and an A/D converter with a 500 Hz sampling rate.

• Figured it was either a bug in the firmware or a bug in the datasheet :-) The problem with testing the firmware is you either need a GPS satellite simulator or a vehicle that can take you to altitude. The latter will be cheaper until the National Helium Reserve runs out of gas (thanks to Congress directing it be privatized).

• It's my understanding that many civilian GPS receivers have an altitude limit of 60,000 ft, ~18 km. 60,000 ft is the upper limit of FAA-controlled airspace, so I guess somebody decided that civilian GPS receivers shouldn't have to work above that altitude. Why anyone who could build a missile that would fly above 60,000 ft would not be able to figure out how to navigate it up there is beyond my ability to feel paranoid.
Edit: Here's a GPS module from uBlox, a Swiss company, with an altitude limit of 50 km and a speed limit of 500 m/s (only works for those really slow ballistic missiles :-). It's their LEA-6 series of GPS modules: