Calcium is easy to test as the reef aquarium suppliers have developed a simple ion specific testing meter. It is sold my American Marine (Pin Point)and is sold at most aquairum retal stores. Some what expensive at $260.
http://www.marinedepot.com/American_Marine_Pinpoint_II_Calcium_Monitor_Single_Item_Monitors_Controllers_for_Saltwater_Aquariums-Pinpoint_Monitors-AM1121-FITEMOID-vi.html There are also many reagent type test kits that run about 25 cents per test to run. Calcium tests are merely titration tests where you add a dye and add acid drop by drop until the color changes.
I have ion specific electrodes for most of the fertilizer chemical tests and also use a Hach spectrophotometer. By far the most expensive testing is with the ion specific electrodes as they do not sell cheap (average about $700 each). They are quick though. Just plug the electrode cord into an ISE pH meter and stick the electrode into the water. Well almost. All the testing equipment and reagents for manual tests and spectrophotometer tests are typically designed for drinking or waste water (they are the major users as EPA requires testing of water and waste water) so your nutrient water very often has to be put in a flask and diluted with RODI water before testing as most tests are for much lower levels such as 20 ppm instead of 200 ppm etc. For an example a high range test for nitarate is 4 ppm, therefore for maesuring the nutrient level you would start out by diluting 10 ml in 90ml RODI water , and dilute 10 ml of that dilution into 90 ml of RODI water, and now do that one more time to beable to get a reading on a nutrent of up to 4oo ppm. I use pipettes that are slim graduated measuring tubes so that I can simply use smaller dilution amounts. ie I can start with 1 ml in 99 ml of ro water for example. In reality I use a digital pipette but those are not commonly used by most people who s do few test as they astar at about $100 each. They are like the ones on TV shows like CSI where the lab tech draws up a little fluid and squirts it into a little vial. Then you just eject the disposable tip so each tip is only used omn one sample or dilution. It is not uncommon to just test the full strength water and if the meter says out of range then it is dumped into a flask and diluted with nine parts of Ro water then a new reading is taken woth the diluted sample. This method continues until you get a readin that is not out of range. Then you just mulitply by the dilution factor. Once diluted is a multplier of 10, if that is diluted then it becomes a multiplier of 100, then 1000 etc. There are reagents with different reanges but none sually have a really high range. The reagenst for use without the Spectrophotomers are genearlly in individual kits with color comparison wheels. the kits run abourt $75 to $150 each. The reading accuracy of the spectropohotometers si not prone to human vision errors and is really the cheapest manner of testing. There is also a hand held meter called a Hach 950 colorimeter, but even used they sell for at least $650 or more. they typically use the same reagent packets as the spectro photometers.
Probably the cheapest manner of setting up a home lab for nutrient testing is buy a used Hach spectrophotomer on eBay. This is a model DR/2000. You can usually buy one for abour $50. Either a DR/200 or a DR/2010 or any number higher than that will test any reagen testable nutrient. Organic nutrients are a different ball game.
The premixed reagents for testing are typically sold for 100 tests. The typical cost is $12 to $25 per 100 tests.
You would need at eBay costs about $50 worth of additional glass ware such as test cells, small flasks and graduated cylinders etc, but all the directions and manuals are readily down loadable for free from Hach.
Few people ever test for the micro nutrient levels so figure testing only for the major and secondary at $25 per eack and $100 for a spectro, meter and acessories that maens about 6 test parameters at (6 * $25 + $100) = $250. add another $25 for each micro nutrient you wish to test for. It sounds like a lot but each $25 is 100 tests. Mixing your own nutrients you will typicallly find that once you have done enough tests to dial in the needs for the particular strain and growing n method you are using you will just mix the formula based on your needs and top off for about aw week and dump as the new nutrient cost is less than the test costs if you have only a small reservoir for one grow room. One test of all six majors is going to cost about $1.50. My nutrient cost is negligible as my water cost for RODI water is higher than the nutrient cost so I base things mot re on that. My water is about $1.50 for a reservoir. So it is a matter of test once aweek and add specific fertilizer or dump once a week. The cost is about the same. So I just use a conductivity analyzer/monitor that runs 24 hours per day and that activates a relay to automatically add nutrient concentrate as needed by a small peristaltic pump. I did run many tests prior to this to determine the highets and lowest demands for nutrients through out the whole grow cycle based uopn indivaidual nutrient declines in the resrvoir daily. I just picked what seemed like good starting ppms for a nutrientt formula and mixed to 1 EC and went from there.
The rest below is sorta out of left field.
Chemical nutrient science and chemical nutrient formulation and chemical nutrient monitoring is a very well known and well documented science. There are no hidden secrets and it is all pretty straight forward. It is one of those beat a dead horse things with some of the old technology growers though that won't let go of old methodologies that do not apply to higher tech grows. The only real changes are just based upon higher technology being used such as better nutrient delivery sytems (aeroponis especially misting aeroponic rather than low pressure systems), air conditioning, HID lighting, dehumidifiers and metered CO2 usage that have changed the nutrient issues. Even then it is merely going through the steps to finf what everyone should find if they are serious growers, "the individual needs of your prinicipal strain based upon the environmental parameters provided by the technologiacal levels of your system." But then there is always the question of are you not provideing the balance you need for optimal plant health and growin efficiency by trying to use an inadequate low techmethod of providing good growing parameters that are insufficient. For example if you have great temperature control, a great nutrient delivery system and great lighting but inadequate CO2 delivery system as you are merely using ventilation but providing high parameters in every other area, things the grow would be much harder to manage than if you just added the extra CO2 needed to match up all parameter levels. This may seem from left field but all things are intertwined so that it seems like when ever you max out one delivery method of one growing requirement then you find another that is lacking.
IMHO Mixtures of low tech and high tech are harder to manage than systems of all high tech or all low tech. Balance is a hard thing to find. Like trying to ride a standard bicycle backwards and forward. Not many well ironed out unicycle growing systems like there are for unicycle s for bike riders.
