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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
im looking for a pH meter for dropping in water, i guess its the delicate glass type. im wanting it to report to a micro controller. Im looking in all the usual places but i see many for 2-400 US$, theres one ive found for 50.
its been 8 years since ive used one, im trying to remember if theres and amplifier in the tip, or in the measurement read-out part?
They need to be kept wet in storage right?
EDIT: looking here:
i just need the glass bit i guess. then build an differential ampilfer.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
ph probes are in two parts, the glass electrode and a temperature sensor. without temperature compensation readings will be inconsistent. You will also need at least two buffer solutions for calibration, preferably three.
i have two of the cheap Chinese 'pocket' type pH meters, so far they seem adequate for my uses.
Due to the expected short lifetime of my probes/meters I store them dry rather than in buffer solution. Definitely do not store in distilled water.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
this was all valuable!
so temperature comp is needed... Is there a difference in de-ionized water from distilled? how long do the live being kept dry?
mine can be real cheap, as i plan to drop them in calibration standards, then drop them in turtle and fish ponds, from my drone. I predict mine wont live long...
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I believe that de-ionized water has the same pH as distilled. If either is stored in contact with air then over time atmospheric CO2 is absorbed and the pH drops a tiny bit.
I don't know how long they last if kept dry, I've only re-started hobby chemistry last year. The instructions with the probes mention that some slight crystallisation around the probe may occur so I guess that over time the reference electrolyte diffuses through the glass I haven't noticed it yet on mine, I've no idea how long these cheap pH meters will last. I guess that small changes can be compensated for by re-calibration but I'm going past my level of expertise here.
For reliability and low weight why not use 'litmus' test papers? Some are available with very fine pH resolution.
At the other extreme, you could retrieve a small sample (tubing + pump + reservoir, or a 'bucket') allowing analysis of any pollutants. This would be the best option as some pollutants need chemical (or radiological?) analysis that would not be suitable as a small payload, and in most cases need sensitive and specific Lab analysis.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Yep I was planning modular drop spool like ability. each mission's instruments would be chosen for its users need. The US navy has "dipping" and sonobouys to detect and kill unwanted Russians.
so GC-Mass Spec would need a small volume of liquid or dissolved solids from a surface.
Id like to fly a machine that drags some cotton across the Chernobyl roof. Then from 11 miles away, see what the GC-MS says.
Wiki :
Special purpose sonobuoys relay various types of oceanographic data to a ship, aircraft, or satellite. There are three types of special-purpose sonobuoys in use today. These sonobuoys are not designed for use in submarine detection or localization.
BT—The bathythermobuoy (BT) relay bathythermographic or salinity readings, or both, at various depths.
SAR—The search and rescue (SAR) buoy is designed to operate as a floating Radio frequency beacon. As such, it is used to assist in marking the location of an aircraft crash site, a sunken ship, or survivors at sea.
ATAC/DLC—Air transportable communication (ATAC) and down-link communication (DLC) buoys, such as the UQC, or "gertrude", are intended for use as a means of communication between an aircraft and a submarine, or between a ship and a submarine.
Particularly :
intended for use as a means of communication between an aircraft and a submarine, or between a ship and a submarine.
seems useful, fleets of drones underwater, and aerial, could colaberate, then report to ship or manned fixed wing.
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pH meter, glass-electronic type.
