Hard to say exactly what is required or possible without knowing what is to be measured. Each compound or element and it's absorbtion lines needs to be looked at to see if it is even possible.
Hard to say exactly what is required or possible without knowing what is to be measured. Each compound or element and it's absorbtion lines needs to be looked at to see if it is even possible.
Personally I'd like to see conductivity, to get a basic idea of what is building up in the tank. Ideally when all is hooked up I'd like to do a 100% turn-over per week of the aquarium water so I doubt I would invest the time in testing nitrites or nitrates past the initial tank break-in time. A pH probe would be nice. An ammonia probe would be nice to warn against spikes -- but not a must-have -- although since it functions similar to a pH probe I imagine the circuitry would be identical? Then it would be mostly peristaltic pumps for the adding of this-and-that, a return pump back to the tank, and lights.
(Too bad the ChemScan wasn't open source hardware, it really is a nice unit. The one at work seems to do a fairly good job.)
I have no experience as far as fish tank chemistry is concerned, but do have quite a bit with analytic instruments and electronics. Measuring conductivity is simple, as is the circuitry for a PH and Ammonia probe. The problem with the probes is that they have a limited lifetime, are fairly expensive, and need to be calibrated. No experience measuring nitrites/nitrates so I don't have any idea how difficult that might be. Peristaltic pumps I have experience with and they are relatively simple.
I believe any analytical instrument, wether it uses probes, spectrophotometry, wet chemistry or another method, would have to be calibrated somehow for the results to be both accurate and/or meaningful.
Yes, I know what you mean about the probes being expensive. pH probes aren't bad, but after that the price starts to soar. How 'limited' are we talking? A couple years? Its things like this that begin to make me understand why we buy cheap throw-away tech from China or similar. (And yes, I did peek at one of the Chinese wholesaler websites. Its tempting...)
For pH probes it depends on the environment. It could last for a few years in relatively clean water, a few weeks or months with some contaminants, or a few days if you let it dry out.
We use pH probes at work, and the two in situ process probes have lasted for years, although I am sure they were expensive to purchase, and the lab probe (which is pretty run of the mill) has lasted for years. The only probes that I can think of that have needed replacement are the so-called rugged field probes. (Apparantly they are not thoughtless user bang around proof.) I work in a place that recycles watewater, so lots of contaminants.
Although I guess it all still boils down to Quality=Cost.
So i'm thinking there are muliple paths to achieve aquarium testing:
Simplest, Cheapest, and the "Wow I wish I had thought of that!" Methods
As far as pH probe life is concerned waste water can range from benign to very harsh. There is a big difference between waste water coming from a pulp mill, ground water leaching from a slag pile, and what comes from a food processing plant. They all contain contaminants, but water from one will shorten the life of a pH probe drastically while the other will barely affect it.
Municipal sewage, food processing plants but no pulp or slag piles. So we're talking a few years at least, which brings me back to an aquarium monitor; what is a good length of time before parts have to be replaced (regardless of which direction the controller takes to get the job done), and what is a reasonable cost? I think the latter question would be harder to nail down, when some people have a couple hundred invested in their aquarium, and others have thousands tied up. Or if price wasn't an issue (AS IF!), would you go for Easiest method of testing, Most accurate, Least expensive, or "WOW!! LOOK AT WHAT I MADE IT'S NEVER BEEN DONE THIS WAY BEFORE!" ?
I really have no idea. As I said a few posts back I am not familiar with aquarium chemistry. At a guess it would be no worse than sewage effluent so the pH probes should last a while. As for testing for other compounds I am not sure what they are or what would be required. Conductivity would be cheap and simple but I have no idea how useful that is.
Hmmm... "what would be required" is a good question, and I asked on an aquarium forum what people test for, and while i'm hoping to get more responses [than 6 lol], the ones I did get range from "everything" from one young aquarist to "maybe a couple things, but only if the fish don't look right" from one user who's had rooms full of tanks for a long time.
So I had another idea for an Aquarium Monitoring Station, one that was extremely modular. Get the basic controller running, with a way to add on whatever analytical doohickey later. Something like a 1-wire microlan, just daisy-chain them all together. What do you think?
Modular is good and since most sensors end up outputting an electrical signal of some sort it should not be too difficult to add modules. Go with the propeller chip for a controller. Not only is it a great choice for the job, there will also be a lot of help available on the forum.
I've been away for quite a while. Good to see some people still getting in on the discussion occasionally. Lots of ideas thrown out there. I still have my 100 gal aquarium but haven't pursued the testing idea in a while.
First: What is to be tested? Ammonia - Nitrite - Nitrate - pH - Phosphates - Calcium - Copper - Magnesium
Second: Probes? Found to be too costly to purchase all necessary equipment. Some require calibration before every use in known solutions. (more cost, more logistics, more engineering to make automated)
Third: Chemicals? The least expensive method. Perhaps on sponge strips or mixed in vials to reveal a certain color change based on ppm substance. Read by a calibrated color sensor.
Fourth: Change water frequently? The simplest way to always know your water chemistry. However, it too is costly to buy the reef salt crystals and is a laborous task on its own. It also removes micro-algae from the water column that my corals would like to eat.
I've opted for the chemical method for the cost and the benefit of spacing out water changes long enough to allow the filter feeders time enough to eat some micro-algae before it gets siphoned out of the tank.
I did some checking a while back into possibly using a mixing block that basically consists of a block of clear ABS plastic that is pre-drilled with the proper channels and openings for injecting, mixing, and dispensing the liquids. I saw some examples from companies that make these for medical purposes. I will see if I can find one to post as an example. These blocks can have pumps, valves, solenoids and all kinds of other very micro devices built right into the block itself. I was thinking even embedding the color sensor so that it could take a reading of the chemicals held in a specific reservoir, record it, flush the reservoir, then fill with chemical #2 etc... The whole thing would be no larger than a hand-held multimeter or something. I'll get more info tomorrow to show what I am talking about.
Comments
http://www.hach.com/hc/search.product.details.invoker/VendorProductCode=LZV479/View=PRODUCT_OVERVIEW/NewLinkLabel=1+inch+Pour-Thru+Cell+Kit+for+DR+5000+Spectrophotometer/SESSIONID|AzVNamszTnpZNE16TW1aM1ZsYzNSWlJFVkZXakV6TUE9PUNEYw==|
Yes, something along that line.
Hard to say exactly what is required or possible without knowing what is to be measured. Each compound or element and it's absorbtion lines needs to be looked at to see if it is even possible.
Personally I'd like to see conductivity, to get a basic idea of what is building up in the tank. Ideally when all is hooked up I'd like to do a 100% turn-over per week of the aquarium water so I doubt I would invest the time in testing nitrites or nitrates past the initial tank break-in time. A pH probe would be nice. An ammonia probe would be nice to warn against spikes -- but not a must-have -- although since it functions similar to a pH probe I imagine the circuitry would be identical? Then it would be mostly peristaltic pumps for the adding of this-and-that, a return pump back to the tank, and lights.
(Too bad the ChemScan wasn't open source hardware, it really is a nice unit. The one at work seems to do a fairly good job.)
Yes, I know what you mean about the probes being expensive. pH probes aren't bad, but after that the price starts to soar. How 'limited' are we talking? A couple years? Its things like this that begin to make me understand why we buy cheap throw-away tech from China or similar. (And yes, I did peek at one of the Chinese wholesaler websites. Its tempting...)
Although I guess it all still boils down to Quality=Cost.
So i'm thinking there are muliple paths to achieve aquarium testing:
Simplest, Cheapest, and the "Wow I wish I had thought of that!" Methods
Municipal sewage, food processing plants but no pulp or slag piles. So we're talking a few years at least, which brings me back to an aquarium monitor; what is a good length of time before parts have to be replaced (regardless of which direction the controller takes to get the job done), and what is a reasonable cost? I think the latter question would be harder to nail down, when some people have a couple hundred invested in their aquarium, and others have thousands tied up. Or if price wasn't an issue (AS IF!), would you go for Easiest method of testing, Most accurate, Least expensive, or "WOW!! LOOK AT WHAT I MADE IT'S NEVER BEEN DONE THIS WAY BEFORE!" ?
So I had another idea for an Aquarium Monitoring Station, one that was extremely modular. Get the basic controller running, with a way to add on whatever analytical doohickey later. Something like a 1-wire microlan, just daisy-chain them all together. What do you think?
First: What is to be tested? Ammonia - Nitrite - Nitrate - pH - Phosphates - Calcium - Copper - Magnesium
Second: Probes? Found to be too costly to purchase all necessary equipment. Some require calibration before every use in known solutions. (more cost, more logistics, more engineering to make automated)
Third: Chemicals? The least expensive method. Perhaps on sponge strips or mixed in vials to reveal a certain color change based on ppm substance. Read by a calibrated color sensor.
Fourth: Change water frequently? The simplest way to always know your water chemistry. However, it too is costly to buy the reef salt crystals and is a laborous task on its own. It also removes micro-algae from the water column that my corals would like to eat.
I've opted for the chemical method for the cost and the benefit of spacing out water changes long enough to allow the filter feeders time enough to eat some micro-algae before it gets siphoned out of the tank.
I did some checking a while back into possibly using a mixing block that basically consists of a block of clear ABS plastic that is pre-drilled with the proper channels and openings for injecting, mixing, and dispensing the liquids. I saw some examples from companies that make these for medical purposes. I will see if I can find one to post as an example. These blocks can have pumps, valves, solenoids and all kinds of other very micro devices built right into the block itself. I was thinking even embedding the color sensor so that it could take a reading of the chemicals held in a specific reservoir, record it, flush the reservoir, then fill with chemical #2 etc... The whole thing would be no larger than a hand-held multimeter or something. I'll get more info tomorrow to show what I am talking about.