Instrument Calibration

I know the instructions said to calibrate the ec and pH meters EVERY time they get used. But the instruments only came with ONE packet of calibration fluid and I was lazy and didn't buy more for about 2 weeks. Here is the moral of this story:

DON'T IGNORE THE CALIBRATION OF YOUR PH/EC/PPM/DO/etc!!!

When I FINALLY calibrated my pH meter today I was shocked!!! When I calibrated my instrument and checked my solution the pH was 4.3. No phreaking wonder I have been struggling with them!!!

I adjusted everything and double checked the instrument calibration. I will NEVER put off calibrating or cleaning my instrument EVER again!!!

Just my sad little story.

On a good note...my plants look OK and are recovering nicely!!!

I wasn't quite sure how often to calibrate. My PPM is locked in, but I calibrate my PH just before I work on my shit. Is that too often? I haven't noticed it wandering thusfar. At most it shows 4.1 on the 4.0 solution, but after a few minutes it goes to 4.0.

Wonder if I should cut back to once a week or once every two days or something.

really hanna says about every 2weeks depending on use

mane2008 said:

really hanna says about every 2weeks depending on use

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Milwaukee says to calibrate "before each use"...if I did that I'd go through like $10.00 in calibration solution per day. I am constantly checking the pH of my solutions.

I figure I'd calibrate every morning, for now...until I get a feel for just how much this thing wanders. I think temperature has something to do with it as well. This time I corrected for temperature...my unit does not have automatic temperature correction.

Right on!

corral hollow kid said:

DON'T IGNORE THE CALIBRATION OF YOUR PH/EC/PPM/DO/etc!!!

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GOD DAMN PESKY INSTRUCTIONS!!!

On a good note...my plants look OK and are recovering nicely!!!

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Well that's good news, anyway! It coulda been a lot worse.

Thanks for sharing an experience that was less than successful. This is how we all learn without having to independently make the same mistakes.

Very brave and well done.

Return of the Spork said:

I calibrate my PH just before I work on my shit. Is that too often? I haven't noticed it wandering thusfar. At most it shows 4.1 on the 4.0 solution, but after a few minutes it goes to 4.0.

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It's smart to cal the pH meter before each use. Wandering 0.1 is not awful but can make a difference in some cases. I prefer to have the confidence that it's bang-on. Getting it wrong is much more costly to me than the 5 mins spent calibrating.

mane2008 said:

really hanna says about every 2weeks depending on use

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I could make a wisecrack about Hanna meters here, but I won't.

corral hollow kid said:

Milwaukee says to calibrate "before each use"...if I did that I'd go through like $10.00 in calibration solution per day. I am constantly checking the pH of my solutions.

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You can use your cal soln for more than one dip!

I keep about 50ml of 4.0 & 7.0 in plastic containers at room temp, the rest in the fridge. I discard the room temp dipping solns roughly biweekly, sterilise the containers and refill from the bulk bottles in the fridge.

I figure I'd calibrate every morning, for now...until I get a feel for just how much this thing wanders.

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You can do that, but the problem is that once you break the habit of calibrating before each use, you'll forget when you last did it. Also, the pH probe does age; they last about 2 years before they need replacement. The get wronger as they're older. An old meter that you may think you should have some confidence in may in fact need calibrated more often than a new one.

I think temperature has something to do with it as well. This time I corrected for temperature...my unit does not have automatic temperature correction.

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Yep, temp is part of the calculation. I'd be surprised if your meter wasn't looking at temp- I think it just doesn't tell you about it. Measuring pH in a solution electronically is really kinda interesting, something wacky to do with the surface tension of the glass in the sensing element creating a voltage in the electrode tip, not totally sure on the specifs of that, will look it up if I get less busy. It's a terribly small voltage induced in the probe tip and the amplifier used to make a useful sig out of it has lots of gain, making it subject to errors, particularly of linearity. That's why 4.0 & 7.0 calibration points are needed. Some meters calibrate on 4, 7 & 10.