pH monitors
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aquaman67
Active member
That was fast.
American Marine returned my e-mail in about 20 minutes on a Saturday, no less.
Here's their response. Italics and emphasis are mine.
The resolution of the PINPOINT pH Meter is 0.01. It may be irresponsible to quote the "accuracy" of a pH meter without stating the calibration material accuracy which is critically important. pH meter accuracy will depend on the calibration fluid that is used. All calibration fluid has a maximum error associated with it and should be stated on the package. The accuracy of the PINPOINT Fluids is as follows:
-pH 4.000 fluid is +/- 0.002
-pH 7.000 fluid is +/- 0.002
-pH 10.000 fluid is +/- 0.005
The error factor of the PINPOINT fluids is literally "off the LCD display" so when the PINPOINT pH is calibrated with the PINPOINT Fluids the accuracy of the instrument is 00.01
Interesting to note that using highly accurate calibration material will not help the final accuracy of a pH electronic that will only display to a tenth digit i.e. 8.1 etc. The accuracy in that case will be +/-0.2 at most
Hope this was helpful....Lou Dell/American Marine Inc.
American Marine returned my e-mail in about 20 minutes on a Saturday, no less.
Here's their response. Italics and emphasis are mine.
The resolution of the PINPOINT pH Meter is 0.01. It may be irresponsible to quote the "accuracy" of a pH meter without stating the calibration material accuracy which is critically important. pH meter accuracy will depend on the calibration fluid that is used. All calibration fluid has a maximum error associated with it and should be stated on the package. The accuracy of the PINPOINT Fluids is as follows:
-pH 4.000 fluid is +/- 0.002
-pH 7.000 fluid is +/- 0.002
-pH 10.000 fluid is +/- 0.005
The error factor of the PINPOINT fluids is literally "off the LCD display" so when the PINPOINT pH is calibrated with the PINPOINT Fluids the accuracy of the instrument is 00.01
Interesting to note that using highly accurate calibration material will not help the final accuracy of a pH electronic that will only display to a tenth digit i.e. 8.1 etc. The accuracy in that case will be +/-0.2 at most
Hope this was helpful....Lou Dell/American Marine Inc.
tgreene
Reefer
There is one vital element that is missing from the above statement, which is for the most part true.
When we buy our monitors and controllers, we must CALIBRATE them before they can be effectively used. We also know that each monitor & controller only comes with 1 sachet of each required calibration fluid. We also know that a 2-point calibration requires that the user go back and forth several times between the 2 solutions. This is where a huge margin of error generally comes into play!
Unless you are sterilyizing your probe after each immersion, as well as using a sachet of new calibration solution each and every time you have to re-immerse the probe, you are contaminating the purity of the sample. Furthermore, unless you have access to a "clean room", there is not nearly enough fluid in each sachet to properly distribute it to enough different testing vials to see your way through a proper calibration. Unless you specifically purchased several sachets of each required solution, you are and will always be working with tainted samples. Unfortunately, you'll likely never see this anywhere in writing, and unless you have lab experience, you'll never know it either.
Herein lies the problem... If your samples are contaminated, then your accuracy is obviously off, and the .1/.01/.001/ or .0001 resolution doesn't mean squat!
FWIW: I actually do keep plenty of calibration solution on hand, because I know about these things.
aquaman67
Active member
Here's an article on how to use Borax to verify pH calibration.
http://web.archive.org/web/20001019...twork.com/fish2/aqfm/2000/feb/bio/default.asp
http://web.archive.org/web/20001019...twork.com/fish2/aqfm/2000/feb/bio/default.asp
tgreene
Reefer
In reading through that article, it appears that if you know your precise temperature and are able to measure to a resolution of 0.001, you still have an error margin of 10% or +/- .1
The grades of Borax as well as the age of the probe will also present determining factors above and beyond the initial 10% allowance as discussed.
Something that I also left out of my previous post, yet alluded to in the "clean room" statement is: When rinsing your probe between immersions, unless you're using RO/DI water with a TDS reading of absolute zero and a container that is of the same cleanliness, you're still bringing contaminants into the equation.
The grades of Borax as well as the age of the probe will also present determining factors above and beyond the initial 10% allowance as discussed.
Something that I also left out of my previous post, yet alluded to in the "clean room" statement is: When rinsing your probe between immersions, unless you're using RO/DI water with a TDS reading of absolute zero and a container that is of the same cleanliness, you're still bringing contaminants into the equation.
smoknreefrs
In Memoriam
i really dont understand your argument....
according to what you are saying, since being in an "unclean" room, or "non-sterile" room (which non are) there are factors that we all have to consider when calibrating our monitors, but, all of what you are mentioning would prove true for ALL monitors. so, with that being said, if we where to have "perfect" conditions and we were to calibrate each monitor using "absolute ZERO tds" ro/di for washing of the monitor before placing it into each different calibratoin fluid, and doing whatever we can do to make the calibration conditions "perfect" for each monitor then the pinpoint would prove to be a better monitor....
so again, what is your argument, i really dont understand what it is that you are trying to prove. by the way, milwalkee calibration fluid isnt that good either...
tgreene
Reefer
Actually, you got my point perfectly!
All things considered, there is no difference between the 2 units other than a "feel good" extra digit on the Pinpoint. Because I've proven the unreliability of testing to levels to .01 in anything other than a clean room w/ perfect calibration techniques, it proves that the .1 resolution with an accuracy level of +/- .2 means nothing, because BOTH units are going to generally fall withing that parameter anyway, simply because of our calibtation techniques..
Also, I have used several different fluids, and find Pinpoint and Milwaukee to be on par with each other, but the stuff you buy in a store is garbage. The worst being the Coralife 7.0 solution.
All things considered, there is no difference between the 2 units other than a "feel good" extra digit on the Pinpoint. Because I've proven the unreliability of testing to levels to .01 in anything other than a clean room w/ perfect calibration techniques, it proves that the .1 resolution with an accuracy level of +/- .2 means nothing, because BOTH units are going to generally fall withing that parameter anyway, simply because of our calibtation techniques..
Also, I have used several different fluids, and find Pinpoint and Milwaukee to be on par with each other, but the stuff you buy in a store is garbage. The worst being the Coralife 7.0 solution.
Unless you are sterilyizing your probe after each immersion, as well as using a sachet of new calibration solution each and every time you have to re-immerse the probe, you are contaminating the purity of the sample. Furthermore, unless you have access to a "clean room", there is not nearly enough fluid in each sachet to properly distribute it to enough different testing vials to see your way through a proper calibration. Unless you specifically purchased several sachets of each required solution, you are and will always be working with tainted samples. Unfortunately, you'll likely never see this anywhere in writing, and unless you have lab experience, you'll never know it either.
Herein lies the problem... If your samples are contaminated, then your accuracy is obviously off, and the .1/.01/.001/ or .0001 resolution doesn't mean squat!
FWIW: I actually do keep plenty of calibration solution on hand, because I know about these things. [/B]
Boy I gotta tell ya... I read this a while ago and I'm still shaking my head. ..
The reason that calibration material is sometimes called "buffer" is the fact that the liquid can be contaminated to a reasonable degree and still hold its degree of accuracy.
Sterilize the probe.... a clean room...lab experience??? Geesh????
TGreen, if you are trying to say that calibration fluid contamination is going to occur anyway so pH meter resolution to the hundreths digit is meaningless.. you're just plain wrong.
If there is going to be an error in reporting pH it will be in the last digit displayed. It's your choice to be the tenths digit or the hundreths digit.
tgreene
Reefer
The reason that calibration material is sometimes called "buffer" is the fact that the liquid can be contaminated to a reasonable degree and still hold its degree of accuracy.
To what degree is considered reasonable, and how would someone know when that contamination level has been exceeded..?
TGreen, if you are trying to say that calibration fluid contamination is going to occur anyway so pH meter resolution to the hundreths digit is meaningless.. you're just plain wrong.
I'm saying that there generally IS much more contamination than people actually realize, and when adjusting the trimmers during calibration to zero out a contaminated medium, the zero is useless, regardless of how many digits are displayed behind the "0."
If there is going to be an error in reporting pH it will be in the last digit displayed. It's your choice to be the tenths digit or the hundreths digit.
If we don't know the error level of the contaminants, then how can we possibly asses the accuracy of the reading..? To say that only the last digit will report an error, is absurd to say the least...
Feel free to shake your head all you want, but conditions are conditions, and the CLEANER and MORE STERILE they are, the better the calibration results will be. Better calibration equates to more accurate measurements, resulting in a lessor margin of error... I think we can all agree on that!
To what degree is considered reasonable, and how would someone know when that contamination level has been exceeded..?
TGreen, if you are trying to say that calibration fluid contamination is going to occur anyway so pH meter resolution to the hundreths digit is meaningless.. you're just plain wrong.
I'm saying that there generally IS much more contamination than people actually realize, and when adjusting the trimmers during calibration to zero out a contaminated medium, the zero is useless, regardless of how many digits are displayed behind the "0."
If there is going to be an error in reporting pH it will be in the last digit displayed. It's your choice to be the tenths digit or the hundreths digit.
If we don't know the error level of the contaminants, then how can we possibly asses the accuracy of the reading..? To say that only the last digit will report an error, is absurd to say the least...
Feel free to shake your head all you want, but conditions are conditions, and the CLEANER and MORE STERILE they are, the better the calibration results will be. Better calibration equates to more accurate measurements, resulting in a lessor margin of error... I think we can all agree on that!
tgreene
Reefer
You're frikkin kidding me right..?
A sachet of 10.01 Calibration solution that is contaminated via the rinse water, will be DILUTED from both the rinse water (water having a relative pH of 7.0) as well as the marginal offset of the rinse water itself, due to the introduction of either 4.01 or 7.01 calibration solution at the time of the rinse.
Lou, you should probably stop now, because I've not mentioned anything that doesn't fall under the most elementary rules of chemistry.
If you're still lost though, don't worry, because the Easter Egg dye will be on all the store shelves soon enough. I would begin with a package of blue dye and a package of yellow dye. :lol:
Codeman00
Premium Member
tgreene...I'm not sure what you're arguing either. Clean room? The calibration procedure is throwing off the accuracy?
The fact is that the Milwaukee has a resolution of +/-0.1 and an accuracy of +/- 0.2 which is crap. The Pinpoint you stated as to probably having an accuracy of just as bad because they didn't publish it. They stated in an email that the accuracy was far better than you or anyone thought when calibrated with their solution. So the Pinpoint has a resolution of +/- .01 and an accuracy of less than that. That's accurate enough as far as I'm concerned.
I sold my SMS 122 because of the +/-0.1 resolution and +/- 0.2 accuracy. The meter could read 8.2 and your tank could be at 7.8? Thats a big difference and I dont want any part of it.
All this clean room stuff and moving one fluid over to the other fluid calibration pack really doesn't make a difference as far as I can see. I'd much rather have the Pinpoints on my tank because they are more accurate as they stated in their email.
The fact is that the Milwaukee has a resolution of +/-0.1 and an accuracy of +/- 0.2 which is crap. The Pinpoint you stated as to probably having an accuracy of just as bad because they didn't publish it. They stated in an email that the accuracy was far better than you or anyone thought when calibrated with their solution. So the Pinpoint has a resolution of +/- .01 and an accuracy of less than that. That's accurate enough as far as I'm concerned.
I sold my SMS 122 because of the +/-0.1 resolution and +/- 0.2 accuracy. The meter could read 8.2 and your tank could be at 7.8? Thats a big difference and I dont want any part of it.
All this clean room stuff and moving one fluid over to the other fluid calibration pack really doesn't make a difference as far as I can see. I'd much rather have the Pinpoints on my tank because they are more accurate as they stated in their email.
smoknreefrs
In Memoriam
im with you codeman...
at this point i think that tgreene has no basis, and his argument holds no water (no pun intended), other than the basis of him just being contrary to whatever is being mentioned, be it fact (the email from pinpoint) or other hobbiest opinions and experiences.....
at this point i think that tgreene has no basis, and his argument holds no water (no pun intended), other than the basis of him just being contrary to whatever is being mentioned, be it fact (the email from pinpoint) or other hobbiest opinions and experiences.....
tgreene
Reefer
Keep in mind that I first owned all Pinpoint monitors and controllers, yet had nothing but problems due to their inability to hold calibration. I was also sick and tired of forever having to replace the probes, due to unforeseen immersion. Why in the world would anyone simply "jump ship" on an alleged superior product, especially after having invested all the money for it in the first place..? You wouldn't, unless there were continuous problems with it! :rolleye1:
Hell, I still use the Pinpoint wireless thermometers, but they seem to have a consistent .4 degree variance from unit to unit. Three years ago I had sent them back to Lou for replacement on 2 separate occasions, but what I received in return was no better. After a lot of frustration and wasted shipping costs, I "settled" with what I have.
I'll always remember Lou as being the guy who doesn't know why his equipment doesn't work, and continued to replace it with equally faulty equipment! :hmm3:
Hell, I still use the Pinpoint wireless thermometers, but they seem to have a consistent .4 degree variance from unit to unit. Three years ago I had sent them back to Lou for replacement on 2 separate occasions, but what I received in return was no better. After a lot of frustration and wasted shipping costs, I "settled" with what I have.
I'll always remember Lou as being the guy who doesn't know why his equipment doesn't work, and continued to replace it with equally faulty equipment! :hmm3:
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