Hydrobuddy calculation inconsistencies

Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
This is probably going to turn into a lengthy discussion but I would like to 1st discuss an obvious problem I am seeing. Maybe I'm missing something...I don't know.

Bit of background first - I've always been a bottled nutes guy but I've spent the last two months reading as much as I could to learn about making my own nutes.
I mixed up my first test batch and my numbers are nowhere close to what HydroBuddy predicted they would be - but more on that later. I would like to start with the following problem I see in HydroBuddy:

Lets take the following recipe: (the ingredients are actually irrelevant)

Note: The water quality parameters are all set to 0.

HydroBuddy 1.jpg

All of the PPM amounts in HydroBuddy are on the 500 scale. If you add up all of the PPM's from the lower left table, you get ~ 667 PPM.
The predicted EC value is shown in the lower right at 1.485. But if you do the math and divide 667 / 500 you get 1.334 EC.
1.33 is way off from the predicted 1.485. I don't understand. 1.485 EC would be ~ 743 PPM. That's a 76 PPM difference.
Can anyone explain this to me?
 
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solakani

solakani

Well-Known Member
HB prediction model probably accounts for values in Gross Error and Instrumental Error columns
 
Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
solakani said:
HB prediction model probably accounts for values in Gross Error and Instrumental Error columns
Click to expand...
I'm going to dispute this:

Gross error is merely a reflection of how far off the actuals will be to the targets. To prove this, set your targets to exactly what the software predicts.
Next, bump your instrument precision way up... Liters to 0.01 and Grams to 0.001. Will not change the large discrepancy between PPM and EC.
 
Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
I just want to make sure that I can trust the data...

I have a larger follow up question regarding my first round of testing...
After preparing 1 gallon each of Parts A & B, I made a test mix using 1 gallon of RO (0 PPM) with 18.9ml of each part. Expected EC was 1.485. Mine came in at exactly 0.8.

This means one or more of the following:
1) I fucked up the measurements when I made the A & B.
2) My scale is inaccurate.
3) My EC equipment is inaccurate
4) The products I purchased are not as advertised.

I went over my notes and I'm pretty sure it's not #1.
I have a pretty high quality milligram scale and am fairly certain it is not that.
I have a pretty nice EC/PH device which I calibrated prior to this test.

This leaves the last option. Perhaps the raw ingredients are not as pure or authentic as they should be. I did a test.

I took the 4 largest contributors, by weight, and made mixes in isolation.
Boiling down the recipe, I was able to calculate what 1 gram per gallon should show on my EC meter according to HydroBuddy's data.

Calcium Nitrate
1 gram per gallon should yield 0.182 EC
My test yielded 0.1409 EC

Potassium Nitrate
1 gram per gallon should yield 0.2775 EC
My test yielded 0.16679 EC

Magnesium Sulfate
1 gram per gallon should yield 0.12 EC
My test yielded 0.0818 EC

Monopotassium Phosphate
1 gram per gallon should yield 0.2715 EC
My test yielded 0.12998 EC

These figures are WAY off. If the products I bought are not pure, that's fine - I can adjust the purity. I just want to know that I can trust the data.
Is anyone willing to mix one gram of the above ingredients from your product and measure the EC and report back?
 
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2

2com

Well-Known Member
Hot Diggity Sog said:
I just want to make sure that I can trust the data...

I have a larger follow up question regarding my first round of testing...
After preparing 1 gallon each of Parts A & B, I made a test mix using 1 gallon of RO (0 PPM) with 18.9ml of each part. Expected EC was 1.485. Mine came in at exactly 0.8.

This means one or more of the following:
1) I fucked up the measurements when I made the A & B.
2) My scale is inaccurate.
3) My EC equipment is inaccurate
4) The products I purchased are not as advertised.

I went over my notes and I'm pretty sure it's not #1.
I have a pretty high quality milligram scale and am fairly certain it is not that.
I have a pretty nice EC/PH device which I calibrated prior to this test.

This leaves the last option. Perhaps the raw ingredients are not as pure or authentic as they should be. I did a test.

I took the 4 largest contributors, by weight, and made mixes in isolation.
Boiling down the recipe, I was able to calculate what 1 gram per gallon should show on my EC meter according to HydroBuddy's data.

Calcium Nitrate
1 gram per gallon should yield 0.182 EC
My test yielded 0.1409 EC

Potassium Nitrate
1 gram per gallon should yield 0.2775 EC
My test yielded 0.16679 EC

Magnesium Sulfate
1 gram per gallon should yield 0.12 EC
My test yielded 0.0818 EC

Monopotassium Phosphate
1 gram per gallon should yield 0.2715 EC
My test yielded 0.12998 EC

These figures are WAY off. If the products I bought are not pure, that's fine - I can adjust the purity. I just want to know that I can trust the data.
Is anyone willing to mix one gram of the above ingredients from your product and measure the EC and report back?
Click to expand...
I duno if you solved your mystery or not. I could check and compare some of those things with you, but I duno if my gear is up to par; it's just blue lab stuff (combo meter, ec and ph), and "my weigh" .xx scales (I think).
 
Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
2com said:
I duno if you solved your mystery or not. I could check and compare some of those things with you, but I duno if my gear is up to par; it's just blue lab stuff (combo meter, ec and ph), and "my weigh" .xx scales (I think).
Click to expand...
I don't know that I solved anything but I ended up separating out some of the ingredients into their own jugs. I'm actually going to be writing a whole post on this very topic this weekend.
 
Mont@n@

Mont@n@

Well-Known Member
Hot Diggity Sog said:
I mixed up my first test batch and my numbers are nowhere close to what HydroBuddy predicted they would be
Click to expand...
Hi there, I have the same situation when I started mixing my nutrients and I’m still having the same question like you. Predicted ec is 1.4 but my meter shows 1.60 so I feel you bro.
I stop paying attention to that and after mixing a batch I do the ro 1 gallon test
10ml of A and 10ml of B (400)
And if ppm or ec comes closed to the previous batch I will used it. I’m pretty sure one time I add to muck MPK and after that I make sure with the gallon test it won’t happen again lol.
I will keep an eye to see your findings,
Good luck bro.
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A

Atomizer

Well-Known Member
Hydrobuddy only makes a guess at the EC. Directly comparing elemental ppm and meter ppm is not a good idea because meters measure EC (electrical conductivity and then convert it to ppm. 1g of calcinit in 1L of pure water at 25C has an EC of 1.2. The elemental ppm of 1g of calcinit in 1L of pure water is NO3: 144, NH4: 11, Ca: 190. You cant add up the elemental ppm (205) and expect to see that number on your EC meter.
 
Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
Atomizer said:
Hydrobuddy only makes a guess at the EC. Directly comparing elemental ppm and meter ppm is not a good idea because meters measure EC (electrical conductivity and then convert it to ppm. 1g of calcinit in 1L of pure water at 25C has an EC of 1.2. The elemental ppm of 1g of calcinit in 1L of pure water is NO3: 144, NH4: 11, Ca: 190. You cant add up the elemental ppm (205) and expect to see that number on your EC meter.
Click to expand...
Shit...I think I may have screwed up then...not sure. I decided to separate out my major parts...Calcium Nitrate being one of them.
I dissolved an arbitrary amount in 1 gallon of distilled water. I then took 1 gallon of RO water and added some amount of the CalNit concentrate to it (probably 10 or 20 ml's) and took a PPM reading. I used this to establish a PPM/ml/g based on the concentration. And then based on that, I calculated NO3, NH4 and Ca. Is what I did wrong?
 
A

Atomizer

Well-Known Member
I use stock solutions to make up nutes but i use weights to calculate the elemental ppm of the formulation. For example, my calcium nitrate stock consists of 500g of chem, dissolved in 4L of RO and then topped up to exactly 5L. I know 10ml of the stock contains the equivalent of 1g of calcium nitrate. When dealing with weights and volumes you have to be mindful as adding 500g of calcium nitrate to 5L of RO is not the same thing. Likewise, adding 100ml of calcium stock solution to a res is not the same as adding 10g of dry calcium nitrate to the same res, you must account for the water added by the stock to the res or it`ll throw your elemental ppm calculation out. Adding a few mls of something to a large res isnt much of an issue but if you are adding 100`s of mls of multiple stocks to a relatively small res, the extra water can make a difference.
 
Hot Diggity Sog

Hot Diggity Sog

Well-Known Member
Atomizer said:
I use stock solutions to make up nutes but i use weights to calculate the elemental ppm of the formulation. For example, my calcium nitrate stock consists of 500g of chem, dissolved in 4L of RO and then topped up to exactly 5L. I know 10ml of the stock contains the equivalent of 1g of calcium nitrate. When dealing with weights and volumes you have to be mindful as adding 500g of calcium nitrate to 5L of RO is not the same thing. Likewise, adding 100ml of calcium stock solution to a res is not the same as adding 10g of dry calcium nitrate to the same res, you must account for the water added by the stock to the res or it`ll throw your elemental ppm calculation out. Adding a few mls of something to a large res isnt much of an issue but if you are adding 100`s of mls of multiple stocks to a relatively small res, the extra water can make a difference.
Click to expand...
I understand what you're saying.
The reason I did what I did is this:

Let's say you dissolve your 500g of Calcium Nitrate into 4L and then top up to exactly 5L. Now lets say you go out and buy 9 more bags of Calcium Nitrate - all different brands. If you mix (10) 5L jugs, what are the probabilities that they will contain a variable amount of elemental PPM? My hunch is that they all will vary a little. That is why I did what I did....to gracefully account for purity differences and variance. If my hunch is incorrect, please tell me.
 
A

Atomizer

Well-Known Member
The manufacturers will have access to labs to test their product so what they state on the bag should be correct, subject to tolerances. If you buy the chems from ebay and they come in plain ziplock bags, all bets are off :) An EC or TDS meter cant measure elemental ppm so you have to trust whats on the label or get a lab test done. A tolerance of a few ppm either way isnt going to make a huge difference unless it involves the micro`s. I only use two brands, Yara, for the main chems (25kg sacks) and Solufeed for the individual micro`s (1kg boxes) . I dont think i could find 9 different brands of calcium nitrate.
 
2

2com

Well-Known Member
Is there a thread or forum where someone learned and shared how to use this app? I mean literally "how to figure out how to use the app itself". The first thing I encounter when after installing it and opening it is issues, multiple pop up windows, more errors. The same as when I tried to use it years ago.
Is there a way to change the font/text size? Who the fuck can even read the 10 page information/instruction portion on this app without getting eye pain/blurring? Is there a way to increase the size of the window, like almost any other app?
I got it for MacOS; issues.
I got it for Windows 10; issues.

I've been using Renfro's excel spreadsheet nutrient profile calculator for a while now. Pretty easy to *use* (bit of effort to get how to add a new product, but instructions are pretty good and, and then - it works).

I tried to look on the scienceinhydroponics website for a some guidance. The only thing I found so far (which is about 10 years old, I think), fails by step 2 (choose hoagland solution. there isn't one listed. so I chose jacks from the list, made sure my screen/options matched what the "tutorial" says, then carried out calculation; 10 popup windows and senseless results).

I thought the difficult part would be understanding the chemistry (don't really need to I don't think), or...I duno - I didn't think just using the app itself would be so difficult, still.

Should I download an older version or something?
 
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