question on digital ph meter

[diazman]

Hi guys. Just got my hands on a single probe digital PH meter. Did all the calibration as per the instructions but when i put it in my tank for readings (tank is in fishless cycle mode) the reading jumped from 7.5 ish to 7.89-7.90 overnight. Is this normal? I do understand that the readings might not be so accurate?

P.s: its my first time owning one though.

[AQMS]

It could be electronic interference from any electronic device around the Ph meter.
Try to test it with and without any other electronic devices switched on and differentiate the reading.

[Urban Aquaria]

Just to narrow the factors, did you do a 2 point calibration using 4.0 pH (or 10.0 pH, if you are measuring more alkaline water) and 7.0 pH solution? Sometimes if only 1 point calibration is done, the readings could be less accurate.

Another reason could be you might have taken a measurement at night and if there is a moderate to high amount of plants in the tank, the pH would tend to be slightly lower (due to the plants respiring Co2)... then if you test in the daytime with lights on, the opposite occurs and your pH rises slightly due to Co2 being absorbed by the plants.

[diazman]

Just to narrow the factors, did you do a 2 point calibration using 4.0 pH (or 10.0 pH, if you are measuring more alkaline water) and 7.0 pH solution? Sometimes if only 1 point calibration is done, the readings could be less accurate.

Another reason could be you might have taken a measurement at night and if there is a moderate to high amount of plants in the tank, the pH would tend to be slightly lower (due to the plants respiring Co2)... then if you test in the daytime with lights on, the opposite occurs and your pH rises slightly due to Co2 being absorbed by the plants.

hi zero thanks for your reply. I've positioned the meter away from my digital thermometer to the far end. So far, no other electronic equipment are available in the tank.

To UA: I did 2 point calibration (one is 4.00 while another is a 6.85 i believe). The tank is just an empty tank with nothing but filtered K1 media and water. However, i added approximately about 8 liters of borneowild shrimp soil the night before. The PH reading down to 7.30 since this morning. :s

Is there a chance the calibration liquid may have expired or something? If so, which calibration liquid should i buy?

One other thing, according to the instructions for callibration, I would only need to adjust the meter using the provided screwdriver when I calibrate using the 6.85 solution. Is this correct?

Just incase for reference, i got this ph meter off ebay

[Urban Aquaria]

I guess if you follow the pH meter's instructions it should work properly.

The Up Aqua brand pH meter that i got at first actually turned out to be faulty (it kept reading lower pH than usual, even after repeated 2 point calibration), i had to exchange it at the LFS for a new unit, then the 2nd set worked properly. The pH calibration solutions i used came with the meter and just labelled 4.0 pH and 7.0 pH.

BorneoWild shrimp soil should buffer the pH to around 6.0-6.5 (could be even lower during the initial cycling process), so maybe double check the pH with a chemical reagent based test kit (ie. API freshwater test kit), those are usually more accurate.

[Kiang]

Abit of out topic.

After usage of the meter, how to maintain / clean it for the next usage?




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[Urban Aquaria]

Abit of out topic.

After usage of the meter, how to maintain / clean it for the next usage?

Its usually recommended to wash the sensor in distilled water, then store it capped with some pH 4.0 solution in the cotton wool.

[Kiang]

Its usually recommended to wash the sensor in distilled water, then store it capped with some pH 4.0 solution in the cotton wool.

Ok. Thanks for the reply


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[diazman]

I guess if you follow the pH meter's instructions it should work properly.

The Up Aqua brand pH meter that i got at first actually turned out to be faulty (it kept reading lower pH than usual, even after repeated 2 point calibration), i had to exchange it at the LFS for a new unit, then the 2nd set worked properly. The pH calibration solutions i used came with the meter and just labelled 4.0 pH and 7.0 pH.

BorneoWild shrimp soil should buffer the pH to around 6.0-6.5 (could be even lower during the initial cycling process), so maybe double check the pH with a chemical reagent based test kit (ie. API freshwater test kit), those are usually more accurate.

Noted on the input boss. Will get some kits on hand to test. I hope the digital ph meter is in working condition though.. lol. Reason why i got my hands on these because they include replaceable probes.

Let's say for argument's sake, if the set turns out to be faulty. Where would the fault lie in? The probe itself or the whole set?

EDIT: I'll will try to re calibrate them when i get back home. Seems like I may have forgotten to take the temperature setting into account. Will update on the situation.

[Urban Aquaria]

Let's say for argument's sake, if the set turns out to be faulty. Where would the fault lie in? The probe itself or the whole set?

Yeah, most problems are from the sensor probes, they tend to be rather sensitive items and will eventually wear out over time too, that's why they are usually made to be replaceable.

[BFG]

Did you take note of the temperature when you did the measurement?

[diazman]

Did you take note of the temperature when you did the measurement?

I didn't. . Gonna head down to c328 and see if i get my hands on extra solutions. Recalibrate them when I get back home.

About the placement, is it okay if i place the probe near an air curtain?

[AQMS]

Pm me if you cant find any at c328.

[diazman]

Thanks bro. Got my hands on 2 buffer solutions. Now. I measured the temperature to be about 27C. The buffer solution mentioned 4.01 and 7.01 at 25C. With +-2. How should proceed about calibrating it?

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[diazman]

Just an update: The Ph meter's probe started thrashing around. Probably arising from a bad probe. Awaiting for a new probe and I'll see how it goes from there.


On a related note, is there a chance the unit itself (excluding the probe) may be faulty?

Also, what are the average price for a decent-solid branded ph controllers?

[Urban Aquaria]

pH meters and pens are usually around SGD$40-$80, depending on brand (usually abit cheaper if ordered from online).

pH controllers are more expensive (those that can connect to Co2 solenoid to control them)... last i checked they cost like a few hundred bucks.

[diazman]

pH meters and pens are usually around SGD$40-$80, depending on brand (usually abit cheaper if ordered from online).

pH controllers are more expensive (those that can connect to Co2 solenoid to control them)... last i checked they cost like a few hundred bucks.

Ah. Now I see the meters and controllers are two separate things altogether. Was confused in the first round when the polyart uncle kept mentioning controller.

Thanks again UA.

[BFG]

Honestly, if you are looking for this type of equipment, look at the American Pinpoint brand. On another note, try using the probe on another plug solely without piggybacking other equipment on the same power point.