Got my Extech 110...Not happy

[TroyG]

Well got my new Extech 110 the middle of last week. Calibrated the unit Friday for cheese making on Saturday. Tested the raw goat milk and PH came to 6.4 exactly so all looked well. I think Michelle took the PH one more time while making her Havarti. Sunday I got the unit out to use while making my cheddar. Right off the PH was 6.7 on my milk which I thought to be odd, but I moved on. Every stage of my cheese making was not hitting my PH numbers which was making me very unhappy. So after ruining my cheddar & wasting 6 gallons of milk I was thinking maybe the calibration was off. So I put it into my Ph 7 solution and it read 10. Then it started flashing renew. Again I thought this was odd since we only used it a few time. I opened it up and only a couple drops went in to the meter. So I tried to calibrate the until again and now it just shows -1.

I can only assume my meter is defective.......  :'(  I bought it from Amazon, but I guess I will call Extech first.

[linuxboy]

Not sure it's defective. Here's the process to use a pH meter with dairy products, every time at the beginning of a new batch:

- Take it out of solution cap, rinse with distilled water and wipe with a tissue paper.
- Do a 2- pt calibration, 7 and 4. Do this every time at the beginning of a make.
- Take your measurement.
- Rinse off again in water. If residue on bulb, wipe gently. Milk is thick, leaves a residue.
- Have a small container of a 7 solution, put the electrode in it, should register 7 again.
- Rinse after every use, if it looks like there's residue, wipe with tissue paper.
- never store dry

From your description, sounds like you didn't calibrate in between makes? And maybe it wasn't cleaned properly? Milk gums up reference junctions easily... it will cake on and form a barrier.

[TroyG]

You are correct I did not calibrate because it had only been used twice the day before. Yes it was cleaned well......I rinsed, used soapy water, rinsed well with hot water, and then used the cleaning solution I bought from Hanna. I have PH4 in the cap with the sponge.

I was being super careful about cleaning after reading about the importance here. 

So each time I am going to use the meter I would do the following?

Calibrate 7 then 4
Rinse
Check in Ph 7
Rinse
Dry
Take reading
Rinse
Dry
Put cap on (Which has sponge with Ph 4)

Sound right? Would it be better to soak it in Ph 4 or just leave the cap on while I am storing the unit?

Thing I did not like most was waiting for the temperature of the unit to match what I was testing. For example I would place the meter on a curd that was 98 it would take the meter 2-3 minutes before it would adjust. During this time my reading was changing.

Extech is sending me a new electrode. Hope that solved the issue.

Oh and I have to take some of the blame for my ruined cheese since I got it way to hot during the Cheddaring process. 

Oh well....Live and learn. 

[BigCheese]

Uh-oh, well I am ordering one of these today...

[wharris]

Call the help desk.  They are very helpfull.
Although, this is not the first time i have heard of this problem with this meter...

[TroyG]

They sent me the wrong electrode so I had to call again. They have since sent me the correct one and i will be trying it out this weekend.

[tananaBrian]

I assume by no follow up that your new probe is working correctly?

- How long does it take for temperature and pH reading to stabilize?
- Do you believe either or both are accurate?

Brian

[BigCheese]

Today I made cheese and used by extech 110 for the first time in 3 or 4 months. Without calibrating, the extech was .01 off in the PH7 buffer solution. Pretty darn good to me! The temp sometimes works slowly, but cheese temps are often not that drastic, so I find it to be fine.

[tananaBrian]

Today I made cheese and used by extech 110 for the first time in 3 or 4 months. Without calibrating, the extech was .01 off in the PH7 buffer solution. Pretty darn good to me! The temp sometimes works slowly, but cheese temps are often not that drastic, so I find it to be fine.

OK ...here's a question for you.  Let's say your Extech PH110 is laying on the counter at 70 F and you've got a make that's 20 or 30 degrees warmer ...how long does it take for your pH reading to stabilize?  Does it measure a stable pH within 10-15 seconds, or does it slowly change while the temperature of the probe adjusts up to that of the make?  How long until your pH measurement is stable?  (Nobody's answered that question for me yet ...including Extech).  I'm wondering what a fair expectation is...

Brian

[BigCheese]

Probably a minute, give or take a bit. Often times I do not wait because I can see where it is headed and that is precise enough for me.

[tananaBrian]

Probably a minute, give or take a bit. Often times I do not wait because I can see where it is headed and that is precise enough for me.

Sounds like some creep is normal.  I experimented with preheating the probe tip under warm running water to get it closer, and it seemed to stabilize faster.  Makes sense I guess.  And I think it takes a little experience to read the thing as well, e.g. calling it 'close enough' when the changes in the reading slow down enough for you to estimate where it might end up ...you know, within 0.05 of actual or so.  On some weekend afternoon, I'll experiment and at the same time, grow in experience.  Can't decide what to make this weekend... a gouda (my first pressed cheese) or maybe LB's moz recipe.  I'd like to make snack curds again, but want to try LB's version for extended shelf life when I can buy a small pack of the required cultures (s. thermophilus and MD88).

Brian

[wharris]

My readings never fully stop.
The change in my reading just slows to a bare crawl.
in about 1 min, the hundredths decimal barely moves 1 or 2 points up or down.

Every so often, if it does not stabilize quick enough, i get nervous.
So I clean the tip with distilled water, and then in a small beaker of pH7.01 calibration fluid. 
so far, It always reads within +-.03 of that...

So, while I may get nervous on a occasion, I have come to trust my meter.

What helps me is that I have a ring stand with a pH meter holder.  That holds it still in the sample.

[tananaBrian]

A stand is one thing that I don't have for the meter, but would like to.  Also, it sounds like my experience is much like yours ...I just need more experience with it.

I think I'll be making a gouda this weekend, although I do have some other projects going on that might overrule having time for cheese.  Hmmm... I think I'll wait on my new cultures to arrive.  I have some standard C101 mesophilic culture that I can use for a gouda, plus I have some MM100/101 coming in the mail that I will use for another gouda right after it.  I want to compare the diacetylactis (MM100/101) to the non-diacetylactis (C101) versions to each other at about the same ages.

I'm making a cheese press as we speak and have a couple of minor details to get my cave ready first though.  Haven't done my first pressed cheese yet ...unless you count cream cheese that was "pressed" by a plate and some weight overnight in a colander ...

Brian