glass-bulb pH meter, time in solution?

simpleleaf

simpleleaf

Well-Known Member
How long do folks leave their bulb-type pH meter in nutrient solution before reading it?

I've been experimenting with different lengths of times over different grows. My most recent was 2 to 4 hour readings. Sometimes I'd let it go overnight. It would depend a lot on whether the value seemed stable. As long as the meter kept changing, I figured, it wasn't yet time to consider it a final reading. I just write the pH on a piece of paper along with the time, and keep adding values at desired time intervals, typically 30 minutes.

I just discovered a flaw with this approach, over time, and particularly overnight, the PPM of the solution increases (as measured by electrical conductivity), presumably due to evaporation. Thus, it seems there should be an upper limit on the amount of time the probe remains in solution before taking the reading.
 
PopAndSonGrows

PopAndSonGrows

Well-Known Member
With my Apera PH-20, I just wait til i see the "smiley face" usually a minute or less

And, I always freshly agitate anything I'm pH'ing, be it nutrient solution or just plain water.
 
HitSolution#9

HitSolution#9

Well-Known Member
simpleleaf said:
How long do folks leave their bulb-type pH meter in nutrient solution before reading it?

I've been experimenting with different lengths of times over different grows. My most recent was 2 to 4 hour readings. Sometimes I'd let it go overnight. It would depend a lot on whether the value seemed stable. As long as the meter kept changing, I figured, it wasn't yet time to consider it a final reading. I just write the pH on a piece of paper along with the time, and keep adding values at desired time intervals, typically 30 minutes.

I just discovered a flaw with this approach, over time, and particularly overnight, the PPM of the solution increases (as measured by electrical conductivity), presumably due to evaporation. Thus, it seems there should be an upper limit on the amount of time the probe remains in solution before taking the reading.
Click to expand...
Untill it stabilizes. 10-20 seconds of stearing it around.
 
simpleleaf

simpleleaf

Well-Known Member
I wanted to revist this thread with what I've learned this past winter. First, I should apologize, I probably should have put this in the novice forum, but here is where I put it.

My cheap pH meters take a variable amount of time to take a reading, sometimes they stabilize quickly, other times more slowly, and I'm not entirely certain why. If they aren't used for some longish time, they take longer to stabilize on a number than if I used them in the past several days.

I've settled on 12 minutes to take a reading. It's also seems very important that the meter sit in calibration solution for the same amount of time as it takes for a nutrient solution reading. If I decide to take a 15 minute reading instead, then the meter sits in calibration solution for 15 minutes, is calibrated, then the reading in nutrient solution is made.

I've also found my pH meters "warm up". I am managing this by recalibrating between every reading, until recalibration shows no need for adjustment. Once they warm up, subsequent calibration solution readings result in the same number.

Recap
1. Remove electrode caps which had storage solution.
1a. Rinse electrode and body of all salts.
2. Calibrate for X amount of time in calibration solution. I've decided that X is best at 12 or 15 minutes, but this may vary.
2a. Rinse.
3. Take pH reading of nutrient solution for the same X amount of time.
3a. Rinse.
4. Repeat steps 2 and 3 until all desired readings are made.
4a. Final rinse.
5. Fill caps with storage solution and store (upright) until next use.
 
Last edited:
Hollatchaboy

Hollatchaboy

Well-Known Member
Bluelab guardian. Just leave the probe in the res. I have 2 probes. I switch them out every week, and i put the stored one in storage solution. Not trying to push it on you, just saying it's really easy, and gives me piece of mind.
 
ooof-da

ooof-da

Well-Known Member
Your calibration is simply setting the curve of free hydrogen and hydroxyl ions in the water. It should take around 20 seconds to stabilize (regardless if in CAL solution or an actual sample) and after that no additional accuracy is being had IMO. Some meters do not compensate for temperature annd will bounce.

Are you doing a 1,2, or 3 point calibration?
Are you trying to read whole numbers (X.77) or 7.X7 or 7.XX?
 
simpleleaf

simpleleaf

Well-Known Member
It takes way longer than 20 seconds to stabilize in any calibration or nutrient solution. These meters supposedly have automatic temperature compensation, ATC.

I'm only using a 1 point calibration, specifically with 6.86 pH salts. I have tried a 2-point calibration, which would include calibration with 4.01 pH salts. However, each time required turning the single calibration screw (not 2 different adjusters or screws), back to about the same position it was in with the prior calibration solution. Hmm, hard to explain in words.

1. Calibrate in 6.86 pH solution, set adjustment screw so display reads "6.9".
2. Calibrate in 4.01 solution, set adjustment screw so display reads "4.0".
3. Test in 6.86 pH solution again, single adjustment screw needs to be turned back to its prior position when it was in 6.86 pH solution.
4. Test in 4.01 pH solution again, adjustment screw needs to be turned back to the position it was in the last time it was in 4.01 solution.

This repetition can be repeated with same results. Thus, the 2-point calibration seems to be a fail. So, my rationale for using the 6.86 solution as a 1-point calibration is that it is closest to the value of nutrient solution.
 
ooof-da

ooof-da

Well-Known Member
Hmmm. Not sure why thy is happening- what meter are you using specifically?

One thing is undeniable- if you “calibrate” your meter but then can’t turn around and read a buffer of 4.01 and 6.86 accurately (+- 0.10), then your meter isn’t “calibrated”.

You’re rational for choosing a buffer closest to the actual real world readings you plan to use it in is solid however if you can’t read 4, 7, and 10 buffers all fairly accurate something is wrong with the curve your meter is holding. Your meter has a curve like a teeter-totter so if you are in a buffer of 6.86, calibrate it at that point (1-pt cal) then go to a buffer of 4.01 and it reads say 5.01 then a buffer solution on the other side of the teeter totter (of say 10) would read around 9.0….ya know?
 
simpleleaf

simpleleaf

Well-Known Member
They're cheap ebay pH pens. I put a photo of a red one and a yellow one in my grow journal some time ago. I have several of the yellow ones, the red one I don't use because it gives me wonky readings.


For me, there were upgrades from pH papers which only had zero-digit colors. Someday I'll get a better pH pen, but for now those are the ones I have. Taking 12 minutes to calibrate, then another 12 minutes to get a reading is a drag all on its own.

Thanks for your thoughts and help. I mainly wanted to update this thread with the procedure that seems to work best with them.
 
Last edited:
N

nxsov180db

Well-Known Member
simpleleaf said:
I wanted to revist this thread with what I've learned this past winter. First, I should apologize, I probably should have put this in the novice forum, but here is where I put it.

My cheap pH meters take a variable amount of time to take a reading, sometimes they stabilize quickly, other times more slowly, and I'm not entirely certain why. If they aren't used for some longish time, they take longer to stabilize on a number than if I used them in the past several days.

I've settled on 12 minutes to take a reading. It's also seems very important that the meter sit in calibration solution for the same amount of time as it takes for a nutrient solution reading. If I decide to take a 15 minute reading instead, then the meter sits in calibration solution for 15 minutes, is calibrated, then the reading in nutrient solution is made.

I've also found my pH meters "warm up". I am managing this by recalibrating between every reading, until recalibration shows no need for adjustment. Once they warm up, subsequent calibration solution readings result in the same number.

Recap
1. Remove electrode caps which had storage solution.
1a. Rinse electrode and body of all salts.
2. Calibrate for X amount of time in calibration solution. I've decided that X is best at 12 or 15 minutes, but this may vary.
2a. Rinse.
3. Take pH reading of nutrient solution for the same X amount of time.
3a. Rinse.
4. Repeat steps 2 and 3 until all desired readings are made.
4a. Final rinse.
5. Fill caps with storage solution and store (upright) until next use.
Click to expand...
If your PH meter takes 12 minutes (or even longer than a minute) to get a stable ph reading you should throw it in the trash and give it a bad review on amazon. Apera meters are what I use, stable readings within 10 seconds.
 
ooof-da

ooof-da

Well-Known Member
it’s probably close to this and won’t take a 2-point calibration. It also is probably not accurate down to tenths (practically) so I wouldn’t trust it to tell you more than if your water is a 6.0, 7.0, or 8.0.
67A0984F-2F2A-4106-BD97-1AADB86AB3DB.jpeg
 
L

Lou66

Well-Known Member
Cheap probes are shit. What's the point of measuring if the error is larger than the precision you need.

Standard lab pH probes cost 100 bucks (just the probes, control unit seperate) and are accurate to about 0.1. Industrial probes that are designed to sit in solution cost multiple times that and are discarded after 6-24 months. With nutrient solutions it would be closer to the 6 months.
There's a reason why these tools cost so much and buying cheap is worse than not using them at all.
 
ooof-da

ooof-da

Well-Known Member
Lou66 said:
Cheap probes are shit. What's the point of measuring if the error is larger than the precision you need.

Standard lab pH probes cost 100 bucks (just the probes, control unit seperate) and are accurate to about 0.1. Industrial probes that are designed to sit in solution cost multiple times that and are discarded after 6-24 months. With nutrient solutions it would be closer to the 6 months.
There's a reason why these tools cost so much and buying cheap is worse than not using them at all.
Click to expand...
I upgraded after chasing pH ghosts around, not the cheapest but I also use it for my hot tub 06BE971F-665D-41AB-B53F-534ACE47566A.jpeg
 
You must log in or register to reply here.
Top