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sinensis

Member Since 18 May 2018
Online Last Active Today, 07:40 AM

Posts I've Made

In Topic: DIY Corned Beef!

17 March 2019 - 08:27 PM

i can't find corned beef pics, but here's a pastrami from scratch. pretty much just corned a prime brisket and then smoked it. this one was good af, but i haven't made it in years.

 

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In Topic: TDS/PPM/PH

17 March 2019 - 02:43 PM

if you have some time, read the study i linked to in my last post. the one about south african mine water.

 

these "total dissolved solids" ("TDS") meters are really electrical conductivity (EC) meters, not TDS meters because that's what they're really measuring.

i am writing "TDS" in quotes to imply that it is not really TDS.

 

it applies a voltage across two probes with known characteristics separated by a known distance and from that it gets the fluid's conductivity.

 

after that, it multiplies it by some number (conversion factor, f) to give you an estimated "TDS".

 

example: "TDS" = EC * f

 

two problems with this.

 

1) it's a lie. the "TDS" (usually in units of ppm) it's showing you is almost never an accurate representation of the TDS of your sample.

one kind of dissolved solid will have a different impact on conductivity than another dissolved solid. pH can affect the conversion factor also.

those conversion factors are commonly determined only for specific dissolved solids (like NaCl for example). if you're measuring a sample that has only distilled water and table salt in it, then it will probably give you a good idea of TDS. if your sample is something else, then the "TDS" value it displays is nonsensical.

 

so if you know what your conversion factor is, you can just do EC = "TDS" / f

 

2) two "TDS" meters (even if properly calibrated) won't give the same reading unless they use the same conversion factor.

that conversion factor i mentioned? there's no standard value for it used by every meter. when you're talking "TDS" with your buddies online, the figures you're sharing and comparing are meaningless unless you're also specifying the conversion factor used by your meter (or by your manual calculations). many meters say what it is in the user manual, but many don't (especially cheaper ones).

 

for these reasons, it makes more sense to just give EC guidelines and not even talk about "TDS"

 

---

 

and how is true TDS really measured? you take a sample and dry it gently in an oven and then weigh the solids that are left over.

 

--

 

also, sorry for derailing you. i hope your kratky gardening goes well.


In Topic: TDS/PPM/PH

17 March 2019 - 02:21 AM

From a small amount of research, it looks as though I'm supposed to be around 5.5 for ph. Does that sound about right?


sounds ok, but maybe research more and wait for others to chime in
 

I am coming up short on PPM research though. Does my PPM level after I add the nutriants depend upon what it is coming out of the faucet? An example would be that straight from the faucet, it reads 200 and I need to add a level of 500 so I'm look for the meter to read 700. These numbers are just for an example, I'm just not sure what level I should be shooting for when mixing nutes.


yes, TDS depends on your starting water. and theoretically, distilled water should have a TDS of 0 ppm.

PS: since you say you are short on research, i say this just as an FYI, not to 'correct' you...
your meter is really measuring EC, not TDS. if it's giving you "TDS" instead, it's really giving you an estimate based on EC using a conversion factor, and you need to know which conversion factor it's using if you want to 100% understand what it's telling you.
 

imo, in gardening applications, people should just speak in terms of EC so everyone's on the same page.

one guy's "TDS" isn't necessarily the same as another's "TDS", and you won't know unless both specify the EC -> TDS conversion factors they're using.

 

this can serve as a decent primer: http://www.scielo.or...502015000400008
 
my research has come up somewhat short as well. here's some of my ramblings when i was playing around with kratky (which i've sort of abandoned):
http://thehotpepper....-noob-concepts/
 
in particular:
 

i don't really understand the implications of EC beyond trying to use it to get some idea of nutrient concentration. i've read some posts with rhetoric about "don't use tap water as it will count towards your EC" as if to say that all contributors to conductance have an equally meaningful impact on plant health. i've probably misunderstood it? i don't get why we're looking at EC all the time instead of just relying on initial gravimetric and volumetric measurements (or better yet, testing for individual nutrients). what can EC tell you if you don't know what's contributing to it? is there some overall upper limit for EC where plants tend to get sick? if anyone can point me in the right direction, i'd appreciate it.  :think:


In Topic: Need opinions on these 2 LED lights

01 March 2019 - 12:34 AM

quantum boards imo are the most elite led grow lights, especially 'official' HLG ones. but it's really hard for me to justify the price for just some peppers or whatever. imho they make a lot more sense if you're growing weed to sell.


In Topic: Unexpected kitchen gadgets

28 February 2019 - 02:20 AM

garbage disposal frozen drink maker, anyone?

 

 

tbh the ignorant part is that they don't seem to know that ice floats