Anyone Else Doing Atmospheric Testing or Interested?

I thought I had posted this before. So I apologize if it got removed for whatever reason. That or the submit didn't go through.

Anyway I was in a huge discussion over flight measurements and motor performance and the subject of effects of temperature, humidity, altitude and all came up. After looking at some charts of how humidity and temperature change rapidly I thought I would start thinking up a setup to measure all this. Similar to what a weather balloon does but in a rocket.

I was just curious if anyone else has done anything like that or what the interests might be in it? I know a couple of altimeters include temperature but I haven't checked to see how fast their response is. In any case I have found some sensors that cover pressure, temperature, and humidity that have fast response.

Either way gives me an opportunity to combine my electronics experience with rocketry. I can use one of my Arduino boards for all the measurements and recording.

Michael

Can you set up the board to do a bluetooth or wifi connection to download the data? That would make it so much easier then having to open the av-bay, retrieve the board and connect it up to the computer to collect data then reassemble the av-bay.

Just thinking. :cyclops:

michaelrmonteith said:

I thought I had posted this before. So I apologize if it got removed for whatever reason. That or the submit didn't go through.

Anyway I was in a huge discussion over flight measurements and motor performance and the subject of effects of temperature, humidity, altitude and all came up. After looking at some charts of how humidity and temperature change rapidly I thought I would start thinking up a setup to measure all this. Similar to what a weather balloon does but in a rocket.

I was just curious if anyone else has done anything like that or what the interests might be in it? I know a couple of altimeters include temperature but I haven't checked to see how fast their response is. In any case I have found some sensors that cover pressure, temperature, and humidity that have fast response.

Either way gives me an opportunity to combine my electronics experience with rocketry. I can use one of my Arduino boards for all the measurements and recording.

Michael

Click to expand...

The NWS conducts over 200 weather balloon flights per day and has been doing it for more than 5 decades, and there are about 1600 flights per day so there is a lot of data. Weather balloons ascent and descent ~5 M/s. Sensors typically have a response of a second or so. Which is typically limited by the time it takes the sensor to equilibrate with it's environment. Unless you plan to only make measurement during parachute descent (which is fine) what type of sensors are you planning to use, what is your definition of fast response, how are you going to do your sampling, and what techniques are you planning to use to improve the sensor response time by 1 to 2 orders of magnitude required for rocket ascent velocities?

Bob

Handeman said:

Can you set up the board to do a bluetooth or wifi connection to download the data? That would make it so much easier then having to open the av-bay, retrieve the board and connect it up to the computer to collect data then reassemble the av-bay.

Just thinking. :cyclops:

Click to expand...

That is a great idea. Probably to start with I'll just have a connector I can plug into from the outside.

bobkrech said:

The NWS conducts over 200 weather balloon flights per day and has been doing it for more than 5 decades, and there are about 1600 flights per day so there is a lot of data. Weather balloons ascent and descent ~5 M/s. Sensors typically have a response of a second or so. Which is typically limited by the time it takes the sensor to equilibrate with it's environment. Unless you plan to only make measurement during parachute descent (which is fine) what type of sensors are you planning to use, what is your definition of fast response, how are you going to do your sampling, and what techniques are you planning to use to improve the sensor response time by 1 to 2 orders of magnitude required for rocket ascent velocities?

Bob

Click to expand...

I will probably have to rely on descent measurements seeing it would require some really fast sensors to attempt ascent measurements. Unless I just account for lag. Humidity is the hardest. Of course every vendor say fast response which in their terms means anything 10sec or less it seems. I need less than 1sec. However I did find some humidity sensors that are down to .3 seconds. There are some out there as fast as 20msec. Response time is actually reduced with increased air flow. Again this is just the beginnings so a lot of research right now into what sensor to use, what methods etc. Depending if the sensor has digital output or if I need to use my on ADC I could still use one of my Arduino boards to do the work. If I'm taking measurements on descent only then I can use some of the Arduino breakout boards too.

I'm moving right now so it's a good time to do a lot of reading of datasheets as well as information on atmospheric research and measurements.

I''ll post a list of some of the sensors in case someone else is interested as well.

BTW here is a good link for soundings:
https://weather.uwyo.edu/upperair/sounding.html

Michael

I conduct experimental environmental measurements and develop instruments and sensors so I'm familiar with the available instrumentation and sensors. I worked on a ozone photometer program our company had with NCAR and delivered a gold standard instrument to accurately and precisely measure O3 concentration at the ppb levels from sea level to over 100 kft. It has flown on skyhook balloons, the ER-2, the RB-57, and a DC-8. It has to be able to accurately sample at 400+ knots so I am aware of the problem that can be encounter at high speed. I also worked on a number of programs that had to measure atmospheric pressure, temperature, and humidity so I know what is available and what works. (Not necessarily the same thing.)

Vaisala make most of the radiosondes and dropsondes used for collecting weather data in the US and globally. There's a lot of good info on their webside. https://www.vaisala.com/en/products/soundingsystemsandradiosondes/radiosondes/Pages/RS92.aspx

As long as you are not trying to collect data on the ascent, you devices only needs the type of sensors used in a radiosonde or dropsonde. The sensors will have to be exposed to the airflow however or you will not get good results for temperature or humidity. Some sensors are effected by ambient light so if you use them you must make sure you incorporate a sun shield to prevent false reading however the sun shield must not prevent atmospheric exchange with the sensor surface.

Response time should be decrease with increasing flow velocity. All humidity sensors relay on an equilibrium water vapor concentration on their surface which changes either the capacitance or resistance. If the flow is stagnant, the local humidity does not change so the sensor will appear to be sluggish. The commercial sondes mount their sensors on a boom so it is exposed to the air flow.

Vaisala used the VariCap to measure humidity. Carbon film sensors are actually better, have a faster response time and larger temperature range, but due to a transcription error on a circular slide rule circa 1970, the first several years of humidity data was incorrect. The NOAA bureaucracy would not acknowledge the error and as a result, were/are discarding 90% of a sondes humidity data. Do some google searches for the history of the dispute. It's fascinating.

it is important that the temperature and humidity sensors have low thermal mass so they respond rapidly to temperature changes. The temperature fall-off is ~6 F peer 1000' IIRC. For a descent rate of 1000' per minute, the temperature is changing about 0.1 F per second. If you check the water vapor content of air versus temperature, you will see that considerable error can occur if the thermal equilibrium times are slow.

You can use a Bosch TMP180 type pressure sensor (used in many rocket altimeters and in our company's FAA certified nano-drone) as the factory calibration exceed the requirements of an FAA altimeter, however when you ascent above 30 kft, a GPS altitude is more accurate.

AT also made a rocketsonde for Vaisala for naval use in the late 90's that use a G80-14. https://www.google.com/url?sa=t&rct...=fZLKlS2t9a7pBfD09uMNng&bvm=bv.87269000,d.eXY

Bob

I've got some rocketsondes that were used in weather research. I'll see if I can take better pictures and post them to a gallery.

Thanks for all the input. I just got my Internet at the new house. Just need a chair now. Lol

This sensor looks promising. Only issue is I have to build the circuitry around it to convert it to an output I can measure.
https://www.saelig.com/product/SE003.htm

The R version is fine as long as it is in the airflow. The L version has too long a time lag for humidity.

The manufacturer should have app notes with circuitry on their website. If not you need a low current ohm meter to measure temperature and a capacitance meter to measure relative humidity.

Bob

bobkrech said:

The R version is fine as long as it is in the airflow. The L version has too long a time lag for humidity.

The manufacturer should have app notes with circuitry on their website. If not you need a low current ohm meter to measure temperature and a capacitance meter to measure relative humidity.

Bob

Click to expand...

Yeah. I was trying to order one and there was nowhere to specify which version so I wrote them already on that issue first. I know they said the lead time is longer for the R version but obviously rather have the wait to get the right part. I didn't find any circuitry on their site but there is plenty to be found and a couple of chip manufacturers that have capacitance to voltage converter chips. Assuming they're accurate enough.

Thanks
Michael

bobkrech said:

AT also made a rocketsonde for Vaisala for naval use in the late 90's that use a G80-14. https://www.google.com/url?sa=t&rct...=fZLKlS2t9a7pBfD09uMNng&bvm=bv.87269000,d.eXY

Bob

Click to expand...

I used to work for Vaisala, and I have a few of the remaining nosecones, some of the G80-14s, also a bunch of G104 and H125 SU motors that they were trying out as well. The company safety officer had no idea all this stuff was sitting in the flammables cabinet and wanted it "disposed of immediately". I offered up our club president to "safely remove" the items and we split the lot. Was a good day.
-Ken