Measuring rain acidity and atmospheric CO2

[herb1942]

Does anyone have any thoughts on a method of measuring the pH of rainfall, and the correct method of measuring atmospheric CO2? I have the CO2 sensors and am concerned primarily about the proper placement of the sensors.

[philcdav]

Hi Herb.

interesting topics. Wonder what type of CO2 sensor u have?

pH is easily measured. The first decision will be manual or auto measuring.

Manual could be simple pH 'test paper' on collected rain. Camlab do 100 strip pack with range 0 - 14 for £11 +VAT

An auto system could be a pH probe set into the rain collector. That may not be too good in Auss. though as the probe tips need to be kept wet (and calibrated), not a problem here in Liverpool, UK

Good luck and please post info

[herb1942]

Phil,
I have a pair of CO2 sensors that I bought from PARALLAX.com for US$19.95 each. These are fairly sensitive and easily interfaced. My problem is the siting of the sensors what height, type of enclosure, that type of question. With all the hype about man-caused atmospheric heating I thought it would be useful to collect a few years of CO2 measurements here in north TEXAS(USA). I am still looking at measuring the conductivity of rain water and seeing if that would coorelate to the acidity. Any thoughts?

[yv1hx]

Herb,

Maybe the WMO have a standard for sitting this class of instruments.

Thinking in loud words, may be in a Stevenson screen at 10 meters (33 fts) about ground level..?

By the way, whats its the CO2 sensor part number?

Measuring the soil humidity is a real nightmare, because there may be a lots of interactions between the probe itself and the soil under test, ruining the measurements. :bash:

[beteljuice]

CO2 sensors should be 4ft => 6ft (breathing height) and well ventilated.

[Gina]

CO2 sensors should be 4ft => 6ft (breathing height) and well ventilated.

Could go in your Stevenson screen then with the temp/transmitter unit

[herb1942]

Good suggestions: Seeing as how I have two sensors I can mount one at the 5-6 ft height and the second off
the roof of my house. I'll post any data I get and enlist help drawing conclusions. The Parallax.com part number for the sensors is: 605-00010. Parallax also has a sensor mounted on a conditioning module (PN 27931) for US$29.99.

[herb1942]

Sorry about the wrong part number and price of the Parallax CO2 module. It should be: part number=27929, and the cost is US$35.99. Mea Culpa

[yv1hx]

Be aware, the measurements can be highly influenced by the moisture and ambient temp.

I have in mind a similar project, using this CO sensor element and some PicAXE microcontroller:

http://www.electronica.com.ve//ventas/c ... 7083a43344

But most semiconductors are hard to find and expensive in my country, this project is stopped by now.

Regards,

[herb1942]

I am also concerned about the effects of temperature and moisture on the accuracy of the readings. If all I want is a quantitive increase or decrease in levels then I would not have to worry about absolute values. If I wanted to compare my results with the rest of the world I should probably calibrate the sensors. I have adjusted them so they read exactly the same value when they are side-by-side. I am going to do some experimenting with measuring the conductivity/resitivity of water with different amounts of acid and a base in the water. Thanks for all the good ideas and I'll make a pair of identical small instrument shelters and redo the circuit to include a temperature sensor and a humidity sensor at each location. I use a DATAQ DI-148U ADC Box that has 8 analog channels and runs off a spare computer.

[yv1hx]

A last advice:

Keep the wires running from the ADC box to remote sensors as short as possible, because they can act as aerials, picking up electrical noise and messing up the readings of the ADC Box.

Also you can use twisted and/or shielded pairs whenever be possible.

[herb1942]

Marco,
For temp sensors and other DC sensors I use CAT5e computer cable and a strong low-pass filter at the ADC. I have a temp sensor at the end of a 50 meter run and before the filter there is a lot of 60 cycle hum but the low-pass has a cutoff of 10 hertz and that takes care of all the noise. For AC up to 50 Megahertz I use twisted pair and differential amplifiers. I buy most of my electronic parts from a few sellers on eBay. These are good prices, but I don't know how the exchange rates work. I use PayPal for all my online purchases if possible and I have a special Debit card that I use so I just put the right amount of money in the account when I want to use it. This weekend I will do a little experimenting with the acidity detector for rainwater and add that to the array of junk I have stuck on the pole. It's REALLY nice to be retired and have LOTS of time.

[Gina]

It's REALLY nice to be retired and have LOTS of time.

It must be I'm retired in the sense that I had a career but as a housewife, retirement just doesn't happen - and we have a smallholding though that's minimal now.

[herb1942]

Gina,
My mother was a homemaker and she figured she was retired when all us kids had moved away, and all she had to put up with was my father. I'm retired because I was let go at Texas Instruments last year and the job market for 68yr old electronic technicians has dried up. Most of the work I used to do has been moved out of the US to where labor costs are cheaper. Speaking of the weather, I noticed on your weather panel that the humidity was 95% and you had no rain. Here in Texas if the dew point gets within a few degrees of air temp it is going to rain.

[Gina]

Sorry you lost your job. Now I guess you have plenty of time but much less money to spend As for me, although there's just the two of us, he's recovering from a stay in hospital and I'm his primary carer. Fortunately, he's doing really well so I may have a bit more time soon to spend on my computer/weather hobby.

Regarding the humidity, it is often very humid here in SW England without actually raining, though we do get a higher rainfall than further east in the UK. Both these factors arise from being fairly close to the sea and with prevailing winds from the SW. The wind gets here first and being on high ground, it rises and drops it's moisture.