Continuing pH metter issues

[DSmith]

I used my Hana pHep 5 (98128) last week by recalibrating with pH 4.01 & 7.01 buffers before each measurement, taking the measurement, and rechecking the calibration in the buffers for drift. In <10 minutes the meter read 4.00 & 7.05. That's ok drift for me and measurements mid-span are hardly affected. I have a spreadsheet tool for adjusting the actual reading to the post calibration check, but frequent calibration makes corrections very small.

Budget $40 for calibration buffers (4.01 & 7.01), electrode storage solution & electrode cleaning solution purchased with the meter. My meter is about 10 months old, only read room temperature samples, always kept vertical in cap full of storage solution, monthly cleaning solution and has proven reliable. Hana replacement electrodes are about $40 when the time comes.

 

[Wynne-R]

I’m happy with my MW101, the one that replaced the SM101 that Kai has. I check it with the buffers but mostly don’t touch the calibration because it’s close enough. I feel bad that Yooper has had such grief with the pH56.

I’m beginning to think that it’s easier to make a decent electrode in a separate probe, standard parts and all. The proprietary pen models are trying to cram a lot into a small space.

Cleaner? I spray rinse with RO water, blot and put on the storage solution sleeve.

 

[DSmith]

A wash-bottle (http://www.midwestsupplies.com/wash-bottle-500ml.html) with distilled water is nice for cleaning the meter when brewing and calibrating/rinising a refractometer.

The Hana electrode cleaning solution is per the instructions. I do an hour soak monthly.

I like equipment with separate readers/probes a lot too (do temperature measurements that way), but took a gamble on the Hana meter because there's no definitive advice about what to get and always the chance of getting a lemon. I don't regret that purchase 10 months later.

 

[Homercidal]

I have that same Hanna and don't seem to have a problem with it drifting, although I admit I have probably forgotten to use it more times than I've remembered! It seems to read about .02 higher than the Bru'n water spreadsheet would predict, but I have recently gotten a new version of the spreadsheet and am eager to give it a shot again.

I use distilled water to rinse between calibration solutions, and before putting away with storage solution. I haven't yet used the cleaning solution, but I've only used it about 5 times total so far. I think I got it for Xmas last year. or maybe my birthday this year (may).

 

[dbsmith]

In lab at school we have used Vernier LabQuest for making real time graphs of pH and temperature. The package is a bit pricey ($329) for the standalone unit, but I'm going to go the cheap route and buy their USB Go!Link, which is compatible with a lot of their probes, such as the temperature and pH ones. You just use their Logger Lite software on your computer so it can act as the standalone. I remember their pH meter working pretty well and being easy to calibrate. The really cool thing is that there are so many other cool sensors that can be hooked up to the link, such as:

Dissolved oxygen sensor
CO2 sensor
Calorimeter
Flow Rate
Calcium-Ion selective sensor
Salinity Sensor
Infrared Thermometer

The list goes on...I think I'm too excited about this! The link was about 60 bucks and I found the pH sensor for $20 on eBay.

I'll check in once I do some testing and let you know how it turns out.

 

[Kaiser]

I don't, however, understand the aversion to automatic calibration. It just makes life easier IMO but each to his own in this regard.

Maybe its just a bad experience that I had with the PH56 which moved me away from auto calibration. I agree that it should make life easier. But it also adds to the price of the meter if you want to have a BNC connected probe, for example.

But you would agree that automated temperature correction is not needed in brewing use?

Kai

 

[grathan]

In lab at school we have used Vernier LabQuest for making real time graphs of pH and temperature. The package is a bit pricey ($329) for the standalone unit, but I'm going to go the cheap route and buy their USB Go!Link, which is compatible with a lot of their probes, such as the temperature and pH ones. You just use their Logger Lite software on your computer so it can act as the standalone. I remember their pH meter working pretty well and being easy to calibrate. The really cool thing is that there are so many other cool sensors that can be hooked up to the link, such as:

Dissolved oxygen sensor
CO2 sensor
Calorimeter
Flow Rate
Calcium-Ion selective sensor
Salinity Sensor
Infrared Thermometer

The list goes on...I think I'm too excited about this! The link was about 60 bucks and I found the pH sensor for $20 on eBay.

I'll check in once I do some testing and let you know how it turns out.

That's great, but their webpage wants $130 for the ph sensor on top of the $61 for the goLink.
$160 for infrared temp sensor
$130 flow rate sensor
$209 DO sensor

 

[dbsmith]

eBay had the pH sensor for 20 bucks, making the total for a pH meter about 80 bucks, which is reasonable. I'm hoping that the other sensors might be able to be found on eBay periodically when I have extra cash to burn. Not having kids is great

Edit: Right now I see DO probes for about 60 bucks on eBay

 

[ajdelange]

But you would agree that automated temperature correction is not needed in brewing use?

I guess I'd agree that you can get by without it but it isn't something that I would want to be without IOW I would never buy a meter that didn't have it unless I was planning to implement ATC on my own in which case the meter would have to have the ability to communicate temperature and mV readings to a computer and any meter that has that ability will also have the ability to do ATC. In other words ATC is automatically a part of any digital meter and I think the advantages of digital over analog are well enough understood that it's not necessary to restate them here. So if people ask 'should I get a meter with ATC?' I answer 'Get a digital meter and it will have ATC'. I've gotten arguments about that advice. There are still those that think analogue is superior to digital and that vinyl records sound better than CD's (they do sound better than CD's with mp3 music on them but that's another discussion).

But what does it mean to be without ATC? It either means that the effects of temperature are completely ignored or that temperature compensation is done manually. Would the consequences of this be dire? No, I don't think so. We are fortunate that we are critically interested in a region that falls half way between the pH's of the buffers we use for calibration. This happy circumstance leads to minimum 'dilution of precision' right where we want best accuracy IOW mismanaging temperature is not a serious problem. The actual contribution to error depends on the particulars of your calibration and measurement i.e. how different in temperature were the buffers, did you manually dial in temperature data, how did the sample temperature differ, what's the isoelectric pH of your electrode, did you ignore the change in buffer pH with temperature, how accurate are your temperature measurements. My overall philosophy is that with available buffers (± 0.02 pH) and reasonably accurate voltage and temperature measurement (0.5 mV, 0.5 °C) the limiting factor is the buffers. Given that I can expect, in that sweet spot, a standard error of 0.02 pH. Cognizant of the fact that this means that there is a 4% chance that my pH measurement of 5.50 is outside the band 5.45 to 5.55 and feeling, as I do, that 0.1 pH can have a noticeable effect on the outcome of a brewing session I don't want to give up any of the available accuracy. Therefore, as I get the error reducing advantages of ATC for free (especially if I do it myself in software) I always use it. Why not?

I'll be the first to admit that I am an 'accuracy freak' (a label pasted on me at the rifle range - not in the lab) and that my views are colored by my fascination with error sources and propagation so that if a reader has more relaxed views about how good a pH meter reading needs to be I won't disagree. I am definitely not saying people should take their non ATC pH meters and use them as Christmas tree ornaments henceforth but rather that if you find similar models of pH meters one with and one without ATC at a modest price differential, buy the one with ATC not so much because you are getting ATC as because this insures an all digital (as opposed to hybrid) design. If you need to stick to bare bones, get the one without. It will still be a valuable tool for you.