ph meter confusion

[keithpgdrb]

I picked up the ph meter that was recommended here because I'm a numbers guy. I dont do so well with the different shades on the ph tester.

My confusion is that it seems the ph meter is effected by light. the instructions say to swirl the meter in the water until it stabilizes. But it never does. every time you move it, it changes. I do the test in a tall clear shot glass. if I move my hands around the meter, the numbers change. If I let the meter just sit in the water, it will stabilize. but its still effected by shading it, or effecting the light around it in any way.

I picked up some standard solution to calibrate the meter, but with the behavior, its pretty confusing.

SO... What is the method to use to get a dependable reading from the meter.

TFTestkits.net

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[Household6]

Came here for this exact reason.

Doesn’t matter what water source I use or what I use to hold the water while doing the test.

And if I take the meter out and immediately retest, every time the test result is lower and lower.

Most recently used mineral water from a gallon jug, a 4” tall straight glass. Went from 8.0 to 5.3 within 60 seconds on 4 tests).

 

[ajw22]

Get an Apera pH20 meter with calibrating solutions. It works much better.

 

[keithpgdrb]

Came here for this exact reason.

Doesn’t matter what water source I use or what I use to hold the water while doing the test.

And if I take the meter out and immediately retest, every time the test result is lower and lower.

Most recently used mineral water from a gallon jug, a 4” tall straight glass. Went from 8.0 to 5.3 within 60 seconds on 4 tests).

looks like we may have wasted 20 bucks. so far the only suggestion is to get a different meter.

if you let yours sit in the water untouched, does it stabilize? also wondering if using an opaque container would be better then transparent glass. seeing as shadows and light effect the result. luckily I have a standard solution. maybe I'll experiment and see if I can come up with a method. it really should be simple. and its not.

how do we go about suggesting to TFtestkits that they should pull this meter from the site?

 

[mknauss]

how do we go about suggesting to TFtestkits that they should pull this meter from the site?

Email == [email protected]

 

[ajw22]

looks like we may have wasted 20 bucks. so far the only suggestion is to get a different meter.

Return it to TFtestkits and request a refund.

how do we go about suggesting to TFtestkits that they should pull this meter from the site?

Contact Us

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tftestkits.net

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[swing4terps]

I'm having the same issue. Was wondering how my pH went from ~7.8 at night, to ~7.0 the next day without adding any chemicals. I typically only test at night and in the same spot, so I've just come across the problem. At dusk, I can test in different spots in the pool with varying sun exposure and get very different results.

For what it's worth, the meter results at night seem to read close to what I get on the chem/shade scale test.

 

[jesse-99]

Unfortunately I've not read good reviews on that particular pH meter. Many of us here use the Apera pH60 or pH20 and have much better results.

 

[mgtfp]

Was wondering how my pH went from ~7.8 at night, to ~7.0 the next day without adding any chemicals

Return the meter, details in the post above yours (assuming you have that same meter).

 

[ajbmtb]

I picked up the ph meter that was recommended here because I'm a numbers guy. I dont do so well with the different shades on the ph tester.

My confusion is that it seems the ph meter is effected by light. the instructions say to swirl the meter in the water until it stabilizes. But it never does. every time you move it, it changes. I do the test in a tall clear shot glass. if I move my hands around the meter, the numbers change. If I let the meter just sit in the water, it will stabilize. but its still effected by shading it, or effecting the light around it in any way.

I picked up some standard solution to calibrate the meter, but with the behavior, its pretty confusing.

SO... What is the method to use to get a dependable reading from the meter.

TFTestkits.net

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tftestkits.net

@Sarah and Nate - check this out!

 

[Sarah and Nate]

This sounds like a defect in your meter, rather than the intended operation. The meter is obviously not meant to be sensitive to light, nor should it drop rapidly upon repeat tests. Can you upload a video to youtube and post it here, or send it to me at [email protected] please?

Reach out to me at [email protected] and I'm happy to refund or replace your meter.
Nate @ TFT

 

[keithpgdrb]

This sounds like a defect in your meter, rather than the intended operation. The meter is obviously not meant to be sensitive to light, nor should it drop rapidly upon repeat tests. Can you upload a video to youtube and post it here, or send it to me at [email protected] please?

Reach out to me at [email protected] and I'm happy to refund or replace your meter.
Nate @ TFT

Hey Nate, thank you. I will try to get a video recorded today and send it your way.

 

[keithpgdrb]

Hey Nate, thank you. I will try to get a video recorded today and send it your way.

just sent videos to your email, and I am currently uploading them to youtube if they dont work.

 

[keithpgdrb]

video links

 

[Sarah and Nate]

I've already helped Keith @keithpgdrb via email but for anyone else who may find this thread in the future and say, "Hey, my pH meter kind of behaves like this!" This is not normal! I don't believe that it's truly light sensitive but something is definitely defective with the meter and for that reason I've sent Keith a replacement meter that works as intended.

Thanks everyone for bringing this issue to our attention.
Nate @ TFT

 

[keithpgdrb]

Received the new meter and it seems to be behaving correctly. One odd thing. I have two ph calibration solutions. One for 7 and one for 4. I calibrated the meter with the 7 solution. When I test the 4 solution it reads 3.3? Weird right? Any ideas? Both solutions kept at room temp.

 

[mgtfp]

pH meters need at least a two point calibration, better three. The calibration at pH 7 defines the offset, and calibration at either pH 4 or 10 (more suitable for pool use) defines the slope of the calibration curve. Best to calibrate at all three. Does that meter only allow a one point calibration?

If your meter is 0.7 off at pH 4, then it will likely be off by a similar amount at pH 10. And off by let's say 0.2-0.3 in the pH 8 region. You can try to adjust a pool water sample with acid/base demand drops to 7.8 or 8.0 using the pH-drop test and then see what your meter shows.

 

[JoyfulNoise]

With one point calibration, most pH meters will only be stable and accurate by about +/-1.0 units. So if it’s calibrated around 7.0, then you can only trust readings between 6 and 8 (and even that’s a bit of a stretch). It’s a functions of the underlying electrochemistry and materials used in their construction. This is why most high end commercial/scientific/industrial probes and their metering electronics use 3-point calibration methods.

 

[keithpgdrb]

I guess I’m confused by the calibration results and method. If I calibrate to the 7 solution, and then calibrate the 4 solution, only one of them will be correct no? Won’t calibrating to 4 just mess up the 7? The unit does come with two separate calibration powders. I assumed you just pick one. I’ll reread the instructions.

 

[mgtfp]

If a meter supports 2 or 3 point calibration then there is usually a process that needs to be followed to ensure which calibration point is being done at a time. Should be described in the manual.