Questions about my new Extech PH110

[tananaBrian]

Hi,

  Just opened the box with my new pH meter in it, the Extech ph110 with refillable probe, and have it sitting in a jar soaking the probe in a 4.0 solution for a few hours (as suggested here).  I have 2 questions:

- Have you folks had good luck with it's built-in digital thermometer?  It is not something you can calibrate, so I wonder if it's accurate enough?

- The manual says that it'll tell you to recalibrate after 15 usages ...but how often should I calibrate?  With each use?  I'll need more vials with lids...

- The manual describes how to refill the probe, but doesn't give a clue on how often or how you can tell when it is necessary ...anyone?

- What is the rinse solution and when should it be used?

Thanks,
Brian

[Tomer1]

Rinse solution is usually just distiled water,
You should rinse the probe after each use.

"The manual says that it'll tell you to recalibrate after 15 usages ...but how often should I calibrate? "
After you get use to using a meter you will get a sense to what kind of numbers you should be getting, When you have the sense its off you calibrate.
Better stock up with calib. solution (4 and 7)

The built in thermometer is usually for the ATC function, It should be fairly accurate.

[tananaBrian]

...Hope I didn't mess the thing up!  I didn't use it for this weekend's make, and the probe has been soaking in 4.0 solution for about 28 hours... ooops.  I think I'll go rinse it, refresh the little sponge for the probe tip and put it away!  I'll calibrate it for the first time right before I use it for the first time.

Brian

[ArnaudForestier]

...Hope I didn't mess the thing up!  I didn't use it for this weekend's make, and the probe has been soaking in 4.0 solution for about 28 hours... ooops.  I think I'll go rinse it, refresh the little sponge for the probe tip and put it away!  I'll calibrate it for the first time right before I use it for the first time.

Brian

Brian, for what it's worth, the company itself recommends storing in 4 buffer.  However, I've read many places - including here, with Linuxboy - that a 3-4M KCL solution is preferable.  Following Pav, I made up a 3.5M KCL solution, and that's what I'm storing the unit in. 

Not that I expect much difference.  I am still really unsure of the accuracy of this thing.

[tananaBrian]

It's been 35 years since I was in my college chemistry classes ...I'll have to look up how to make a 3 to 4 molar KCL solution.  I'll search this forum to see what I can find.  And yes, I did notice in the manual that a ph 4 solution is their recommended storage solution.

Thanks!

Brian

[linuxboy]

I'll have to look up how to make a 3 to 4 molar KCL solution.

Take KCl and water, and boil the water. Add KCl until it will dissolve no more. Let it cool. There may be some crystals at the bottom. Decant, leaving those behind. You now have saturated KCl solution, suitable for storage of Ag-KCl probes. Don't even need to do the math (you could if you wanted).

[tananaBrian]

Thanks.   I just used the meter for the first time, on cheese that is, last night and this morning.  I'm having the same problem that some others have written about and I just wrote to ExTech about it as well.  The reading that I get right after the display quits blinking continues to creep to a new reading as you watch, as does the temperature (expected), and the temperature seems off by at least 5 degrees when it stabilizes.  I haven't seen the pH reading stabilize yet but am currently, as we speak, leaving the probe in the curd (hung by it's string) to see if it ever does.  Example:  I'm making Ricki Carroll's neufchatel recipe.  The gallon of fresh milk, with pint of cream added (and the CaCl) measured 6.66 right after the display first quit blinking ...but then the display kept creeping higher.  I pulled it out at 6.73, rinsed, recalibrated, tried again ...same results.  The display keeps creeping higher.  Similar results this morning, but in the other direction.  The temperature stabilizes at 77 F but the milk is at 72 F.  The initial reading when the display quit blinking was 5.25 and after 10 minutes or so had crept downward to 4.88 and dropping.  Still waiting to see how low it will go.  I expected the fresh milk to measure around 6.6, and it did right at first before the meter reading crept higher, so I thought maybe the reading that you get immediately after it quits blinking is the right one to use?  But his morning, I expected the pH to be headed toward 4.7 (the pH for draining the whey) ...but the initial reading was 5.25 and then dropped as stated... opposite of last night.  Maybe you don't use the initial reading, and maybe the meter is asymptotically approaching the right reading?  Don't know... but it's confusing.  Yes, the probe tip was stored in a pH 4 solution all along, and I soaked it in pH 4 solution for 10 minutes before using it (as described by the manual.)  Calibrations were 3-point calibrations, calibrated with 7, then 4, then 10 as the manual described.  Anyone?   Hmmm.... I'd like the meter to be easy to use, read a correct reading within 10-15 seconds (NOT 10-15 minutes), and to be reliable.  If not, then I'll ship it back...

Brian

PS: More info... the pH meter timed out and shut off while I was waiting for it to stabilize, but when turned back on, it read 78 F (should be 72 F) and a pH of 4.54.  Cleaned, dried, measured again ...this time, no time wasted waiting for temperature to stabilize and the pH appeared steady (more or less) at 4.59 to 4.60 ...seemed a bit acidic for 13 hours of mesophilic in 1 gal + 1 pint of milk at 72 F (initial temp 80 F, covered with a blanket while sitting overnight).  Maybe should preheat the pH meter to something close to the milk/curd/whey prior to measuring?

[smilingcalico]

Any more word on your experience? Has it gotten better, or did you send it back?

[tananaBrian]

...Haven't tried using again since the first trial.  They told me to try the 3-button hold and power cycle trick, and if still having problems to put new batteries in it.  BUT, I've been fairly busy on other projects around here and have been on the road for the last 9 days as well.  I'll probably be using it this coming week or weekend though... and will update here.

Brian