pH probe calibration fluid question...

[deynon09]

I bought a hand-held probe a little while ago and was wondering what is the difference between the different calibration fluids. Mine came with a 4.00 and a 6.50(?) calibration fluid bottle. On Bulk Reef, they sell the 4.00, 7.00 and 10.00 fluids. What are each one used for? Different temps?? Which one should I get through the group buy? My probe didn't really come with any good directions and it was cheap... maybe a mistake on my part, but it works pretty well for now.

 

[UncleJT]

4 and 7 are typically used for freshwater applications where the expected target range will be much lower than that of saltwater. For saltwater, for the best accuracy, you want to use 7 and 10 as your target pH range is in the low 8's.

 

[deynon09]

7 and 10, or 7 or 10

 

[Jim Tansey]

When you calibrate a pH probe or almost any instrument you want to establish zero and span points, in the case of the pH instrument it would require two points 4.00 and/or 7,10. The 4.00 is a must and you can choose either the 7 or 10 for the span point, I like the 7 as its closer to our measured values.

Jim

 

[UncleJT]

7 and 10, or 7 or 10

7 AND 10 - you always have to calibrate pH probes with two samples to ensure accuracy.

 

[UncleJT]

The 4.00 is a must and you can choose either the 7 or 10 for the span point, I like the 7 as its closer to our measured values.

Jim, in saltwater, it should really be 7 and 10 as our typical target pH range is within this "window". 4 and 7 would not have us in this window at all as the majority of us strive for a pH of around 8.2 to 8.4.

 

[deynon09]

OK, that makes sense.

 

[Jim Tansey]

4.00 is included in almost all kits because it's the point at which the pH probe has a zero voltage output, to set the span point the 7 is plenty close enough to our point of intrest.

Jim

 

[UncleJT]

4.00 is included in almost all kits because it's the point at which the pH probe has a zero voltage output, to set the span point the 7 is plenty close enough to our point of intrest.

but I have Hanna documentation that states "calibration should be performed with at least two standard buffer solutions that span the range of pH values to be measured.". So Hanna has been lying to me all these years? I've been using 7 and 10 for over 10 years. ::

 

[reeferpj]

all 3 for me there 1.99$ 6.00$ not to bad for what it is

 

[Jim Tansey]

Don't get your panties in a bunch, but the 4 pH point is very important in establishing the health of the probe, as I said its the point at which the probe should have a zero voltage output. Hanna has not been lying to you if you prefer 7 & 10 it will work fine, but if the object is to adjust the slope (and with two points its all we can do) wider is better. I am not addressing errors due to nonlinearity as no manufacture that I have seen address the issue.

Jim

 

[Jim Tansey]

I must correct my statement pH of 7 is the zero voltage output point not 4 as I stated.

Jim