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Miscellaneous Debris => Weather sensors, design, analysis, discussion, home brew => Tech Corner => Barometers => Topic started by: SLOweather on March 15, 2016, 02:41:34 PM
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The HCA-Baro SIL package sensors I ordered arrived from Germany yesterday.
(http://www.first-sensor.com/cms/upload/productimages/products/hca-baro_drucksensoren.jpg)
I got the 4 lead SIL package, as I only need the analog out, not the I2C interface.
I haven't yet jacked it into my bench RUG9 to play with, but I did set it up in a breadboard (did anyone else here ever use real breadboards in the past? That used to really honk off my mom..).
The range is 0.25 volts - 4.25 volts (4 volts) for 800-1100 millibars absolute (mba), or 0.133 volts per mba.
Right now the reading is 3.137 volts, which equals 235.86 mba. Add on the 800 mba offset and you get 1035.86 mba.
Now to go check the local airport and get the correction...
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And....?
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And....?
Currently waiting on a reply from First Sensor on a couple of questions and out squiring my Dad to an appointment. Film at 11...
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Just anxious to know how this chip works and how close it tracks your local measures.
PS I know how the moving folks around goes! Never as planned in my case(s).
Dale (waiting with bated breath)
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OK, current KSBP baro 1012.7, current First Sensor baro ~4.4 miles away and an indeterminate # of feet elevation difference, 1028.0.
Looks like I need a -15.5 correction. I'm higher, so I think it should be a positive correction.
Ordinarily, the discrepancy would bother me, but since this is an analog voltage out, I'm OK with it. It would be interesting to see what the I2C reading is, but I don't have anything set up for that.
I did by 2 of them (one for a spare). I'll have to see what the other one reads.
I also want to program up a data logger module and trend graph and see how that looks.
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I did by 2 of them (one for a spare). I'll have to see what the other one reads.
Yeah, the raw reading out of the first one is 3.031 volts, at the same time the second one is 3.041 volts, so clearly I'll need to add a correction factor.
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OK, yesterday I added the programming to convert the output voltage to millibars, add in the 800 mb offset, and then add in a -21.3 mb correction. It's been tracking the KSBP barometer quite nicely. Right now, KSBP is 1018.5. the First Sensor is 1018.47.
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Thanks for the ongoing updates, it is interesting to see what the newer devices have come up with for options for designers and hobbyists.
I wish some of these accurate and pretty easy to set up goodies would have allowed the Heathkit =5001 designers to put on the market if they were available then.
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Thanks for the ongoing updates, it is interesting to see what the newer devices have come up with for options for designers and hobbyists.
I wish some of these accurate and pretty easy to set up goodies would have allowed the Heathkit =5001 designers to put on the market if they were available then.
You're welcome. What type of transducer did the Heathkit stations have?
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Ah, things weren't tracking the way I thought the should.
After some thought, I realized that a small miscalculation/misunderstanding on my part has caused me to redo the setup and calibration of the baro sensor.
The range is:
0.25 volts = 800 mb and
4.25 volts = 1100 mb
I had zero and span on the analog input messed up. So, I'm redoing things and restarting my calibration check.
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AGain, thanks for the update I've not dug out my 5001 schematics and parts list to see what the baro sensor was for the unit.
I know it would be tantamount to a major redesign to get this unit to output in a range scaled to work, but when I get to it, I'll find the parts list to see what the specs were on that old baro unit.
Thanks for the updates. Dale