- Thread Starter
- #21
OP
Yes but if they both read calibration fluids the same, they should be closer.
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What ph number to believe
- Thread starter Lionfish hunter
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Best bet is to soak both the probes in cleaning solution for 1/2 hour, then rinse in rodi and leave in a storage solution overnight..
Then recalibrate both using the same fresh calibration fluids at 7.01 and 10.01 and see if they differ using a different buffer, you could use a Borax solution and see if they give the same number.
Actually not true...hence why these products are frustrating for many.
- Thread Starter
- #25
OP
Ph matters, my aquarium consumes significantly more alkalinity at very high ph than it does at a low ph. More consumption equals more growth. I have put in significant time and money to raising my ph, it would be nice if I actually knew what the ph was. I have bought just about every ph test and probe available, and still can’t say wether my ph is 8.1 or 8.3.
My Neptune PH probe for the birds. Currently says 1.8. I mentioned this to Neptune at MACNA and they said to replace probe every 2 years- Boy, is THAT COST EFFECTIVE !!!I now have a GHL profilux ph probe and a Neptune apex ph probe. And I am no closer to knowing what my actual ph is. Both are calibrated and confirmed to read correctly in their calibration fluid. But in the aquarium they are almost .3 different! How can this be? If they both read the same in calibration fluid, how can they be that far off?
I have attached screenshots of the Neptune ph in calibration fluids 7 and 10 fluids and in the tank ph reading 7.95. Also screen shots of the GHL ph probe in calibration 7 and 9 fluids and the tank ph reading 8.21. I let the probes sit in their calibration fluid for 10 min before taking screen shots to ensure the probes were at the correct level.
What was your expectations with products that are +/- 0.2 accuracy?
- Thread Starter
- #28
OP
Where does it say a ghl probe has a .2 accuracy? Not saying you’re wrong, I just don’t see it on their website.
Their website says “All GHL measurement electrodes are made of the highest laboratory grade. They are durable, low maintenance, and matched to the highest German quality standards.”
Highest laboratory grade to the highest quality standard seems like it should be more accurate than .2.
Also note that most of these products confuse accuracy with precision and report a 0.01 accuracy when they mean precision.
Thread 'What is the accuracy of the GHL pH Probe?' https://www.reef2reef.com/threads/what-is-the-accuracy-of-the-ghl-ph-probe.834819/
They claim +/- 0.1.
I've actually switched to a Milwaukee MA911B/2 pH Electrode/Probe for use with my GHL. The GHL pH probes have been more trouble then they are worth.
My advice stands - You are chasing a decimal point that A) does not matter and B) is not within the repeatable resolution/error of the devices and methods that you are comparing.
A LAB GRADE probe is useless unless it is paired with a LAB calibration... where two points are not calibrated, but a dozen or dozens and the probe readings filtered through the calibration file to adjust the output values....or the PROBE costs HUNDREDS or THOUSANDS of dollars, as does the instrument reading it.
These are hobby toys, not LAB instruments.
- Thread Starter
- #33
OP
If I was confident they were accurate to .1, I would be okay with that. I am not.
- Thread Starter
- #34
OP
“Highest laboratory grade” from ghl. I am not chasing a number outside the devices claimed resolution, I would be okay with .1 off. I however think 1 of them is more than .1 off and do not know which.
You keep repeating the same thing.. but I don't think you are listening to what anybody is trying to explain.
- You are definitely NOT going to get .1 repeatability or accuracy between these different devices and methods.
- You are also not very likely not going to get .1 repeatability with any single one of them.
Do you understand precision vs resolution and error rate/accuracy?
+/- 1 means that an actual reading of 4 5 or 6 is within the margin of a REAL value of 5.
If two devices are +/-1 and the real value is 5 one device may read 3 and the other to 5 Both are within 1.
If one of those devices is +/-1 and the other is +/- 2 then you could have a reading of 4 on one and 6 on the other and both would be within their accuracy margins, but YOU are confused because they are not the same.
- You are definitely NOT going to get .1 repeatability or accuracy between these different devices and methods.
- You are also not very likely not going to get .1 repeatability with any single one of them.
Do you understand precision vs resolution and error rate/accuracy?
+/- 1 means that an actual reading of 4 5 or 6 is within the margin of a REAL value of 5.
If two devices are +/-1 and the real value is 5 one device may read 3 and the other to 5 Both are within 1.
If one of those devices is +/-1 and the other is +/- 2 then you could have a reading of 4 on one and 6 on the other and both would be within their accuracy margins, but YOU are confused because they are not the same.
- Thread Starter
- #36
OP
I am not confusing precision with accuracy. The manufacturer claims .1 accuracy. And a hobbyist claims they meant precision and screwed up. I never said they will be accurate to .1. But that IS what they claim, and for how how much they charge, and for how much they cost, .1 is not an unreasonable expectation. Considering how drastic of a difference 8.3 is compared to 8.1 or 8.5 is to 8.3.
- Thread Starter
- #37
OP
I have never had a problem with drifting precision nor have I claimed to. My concern is accuracy and have never said anything else.
I'm definitely not confident you get +/- 0.1 with GHL, and in my experience, they go out of calibration fairly quickly with lots of drift. I've been happier with my Milwaukee probe on the GHL...but time will tell.
- Thread Starter
- #40
OP
Thank you for sharing your experience. I will consider this.
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