New Extech 110

[clherestian]

My new Extech 110 arrived in the mail a couple of days ago. I tried it for the first time today. I believe it is not working correctly.

For starters, the temperature is displaying about 6 F lower than my other two thermometers. I know the other thermometers are accurate. So that means the adjustment to the ph for the temperature is incorrect.

Secondly, if I take a ph reading of milk, the ph display keeps going up for over a minute and a half. it might keep changing for longer than that, but I got tired of waiting.

Thirdly, the meter says my cheese became less acidic (higher ph) as the make progressed. After adding culture and ripening for 90 minutes, then adding rennet letting it set for 40 minutes, cutting  curds and healing for 15 minutes, it says the ph was .25 higher than when I started.

I am gong to try calling Extech and seeing if they will replace it.

[wharris]

Seems like i've heard this more than once. 
All I can say is that I pretty happy with mine, but i am dissapointed in all the reports i keep hearing.
I cannot emphasize enough how important it is to me, that one trusts in their gear.
I am on the verge of revoking my recommendation of this meter.

To their Extech's credit, Extech is really good about replacing bad gear.

[acstokes]

I have an Extech and am pleased with it. Did you calibrate it using both a 7.0 buffer and a 4.0 buffer without turning the meter off between each buffer? When I first got mine I calibrated with both buffers, but I turned the meter off between each calibration and as a result my readings were inaccurate. If calibrated properly, the buffers used will show on the bottom left of the display screen.

[iratherfly]

I hate using these things to begin with. By the time they figure out my curd's pH after all the time consuming calibration and expensive buffering action, I can just see the curd, smell it, touch it and know if it's good or not... I think that as long at this isn't a food lab and there is no such thing as an instant read pH meter I can't trust it. I have so far only lost cheese to these meters instead of trying to feel it and getting it perfect.

But if you must...
- Calibrate it to 4 and 7. Do not calibrate to 10
- Make sure your probe is clean stored in liquid (distilled water?)
- Calibrate the thermometer to an analog mercury thermometer. If you have auto-correction for temperature in your meter and your thermometer is out of whack than your pH readings will be too
- Make sure the device is on pH test mode and not testing something else such as mv or alkaline (which would give you reverse results than pH)

What cheese are you making? Can you do it without the meter? I olly use it to document what I do so I can track back errors. I never change my cheesemaking based on it.

[clherestian]

Well, everything seems to have corrected itself except for the temperature reading. I guess the meter just needed to "warm up."

About the temp, there is no way to calibrate it.

I do have one question for everybody. Is it a big deal if the temp is off by 5F or so?

[wharris]

How do you know your other tempertures are correct?  How are your other thermometers calibrated?

If you are absolutely sure that your pH meter is registering the wrong temperature, then I would return the meter for one that is correct.

[Sailor Con Queso]

Because it has been sitting in a box on a shelf somewhere for who knows how long, I find that a new probe does better if you soak it in pH 4.0 solution for 24 hours before calibrating. Then always be sure you store the probe with pH 4.0 in the storage cap. NEVER let the probe dry out. Totally unnecessary, but if you want a REALLY good calibration the solutions should be heated to about 90F to approximate the range for starter temperatures.

A temperature difference of 5 degrees will have little effect on pH compensation.

I disagree with Iratherfly. I calibrate to 7 then 4 then 10. A 3 point triangulated calibration is always more accurate than just 2 points. I never make cheese without a pH meter. To me it's just added security to keep from really messing up a good cheese. This is especially true when experimenting with new cultures or combinations.

[acstokes]

Because it has been sitting in a box on a shelf somewhere for who knows how long, I find that a new probe does better if you soak it in pH 4.0 solution for 24 hours before calibrating. Then always be sure you store the probe with pH 4.0 in the storage cap. NEVER let the probe dry out. Totally unnecessary, but if you want a REALLY good calibration the solutions should be heated to about 90F to approximate the range for starter temperatures.

A temperature difference of 5 degrees will have little effect on pH compensation.

I disagree with Iratherfly. I calibrate to 7 then 4 then 10. A 3 point triangulated calibration is always more accurate than just 2 points. I never make cheese without a pH meter. To me it's just added security to keep from really messing up a good cheese. This is especially true when experimenting with new cultures or combinations.

I agree with all the above.

[iratherfly]

If your temp is off, your buffer reading during calibration will be off.

As for Wayne's question - how do you know it's off. As I mentioned, you will need to calibrate according to an old school mercury thermometer. These are always perfectly accurate. It actually says so on my Extech 407227 manual

[woodsman]

It still make sense to check the accuracy of your mercury thermometer - not every one of them is a lab calibrated item.

[clherestian]

I guess I'm not 100% positive the other thermometers are correct. But I did calibrate the digital one in both boiling water and ice water. The other thermometer always reads exactly the same as that one.

I will take sailor's advice and soak the probe for 24 hours.

[acstokes]

I guess I'm not 100% positive the other thermometers are correct. But I did calibrate the digital one in both boiling water and ice water.

I also like to check my thermometers against a fever thermometer since they are normally very accurate and operate within a narrow range.

[Sailor Con Queso]

At pH 7.0, the isothermal point, there is NO theoretical temperature compensation. A calibrated meter will read the same pH 7.0 at 2 degrees or 200 degrees. That's why you always calibrate to a pH 7.0 solution first. That's your baseline. The farther you get from pH 7.0 then the greater the error and the need for compensation. However, within the ranges that we test for temperature compensation is negligible and meaningless for most people. Even at pH 5.0 you are only talking about a potential error of just .06. Most consumer meters are just not capable of compensating closer than .01-.02 so it is not necessary for the meter to be deadly accurate on the temperature reading. So if the meter knows that the pH is within a statistically acceptable range, there is no need for any temperature compensation.

[clherestian]

Sailor, thanks for that piece of info. Very helpful.

[KosherBaker]

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Here's the link to the products:
http://thehumansolution.ecomm-search.com/search?vwcatalog=thehumansolution&query=ph&x=0&y=0
Link to the coupons:
http://www.thehumansolution.com/spofandco.html

Has anyone ordered from these guys before?