Handheld meter - pH / mV / ion / Temp

rodpp

Member
Apr 10, 2019
10
Brazil
Hi!

I have a pH meter that is not used in a long time. The brand/model is Denver Instrument UP-25:




Brochure: http://www.denverinstrument.com/denverusa/media/pdf/literature/ultrabasic.pdf
Manual: http://www.denverinstrument.com/denverusa/media/pdf/Op-Man-UP-Long-RevA.pdf

Specs:
Code:
Modes                    pH/mV/Ion/Temp
pH Range                 0.00 - 14.00
pH Resolution            0.01
pH Accuracy              0.005pH
Temperature Range        0.0 - 100.0o C
Temperature Resolution   0.1o C
Temperature Accuracy     0.2o C
mV Range                 -1800.0 to +1800.0
mV Resolution            0.1
mV Accuracy              0.2 mV or 0.05%
Relative mV mode         Yes
Ion Range                0 to 99900
Ion Resolution           3 sig. figs
Ion Accuracy             0.34%

I bought today three pH buffers (4, 7 and 10) and a KCl solution, and I´ll try to put the meter to work.

I have two questions:
1- Maybe I'll need to buy a new electrode to replace the old one. In the local store there is a pH electrode specified to low ionic strength, and it is more expensive than the regular one. Is this characteristic relevant to measure swimming pool water?

2- Are the other parameters measured by this meter (mV and ion) relevant to swimming pool water treatament?

About the mV parameter, the manual says: "You use millivolt measurement for electrode diagnostics, titration or mea-suring redox potential (also called ORP, oxidation reduction potential). ORP measurements indicate the oxidizing or reducing capability of a solution.You can use ORP values to monitor or control solutions requiring a setamount of oxidants or reductants."

About the ions, it says: "In ion mode you can measure the concentration of specific ions using an ion selective electrode (ISE).The concept is the same as in pH mode where the activity of hydrogen ions is measured with a pH electrode."


Thanks!

Regards,
Rodrigo.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,864
Tucson, AZ
Almost all pools have HIGH ionic strength water, not low.

ORP can be correlated to FC but if you have high CYA levels, that will interfere with an accurate measurement. ORP can vary a lot with other parameters.

ISE’s (ion selective electrodes) can be very expensive. A simple pH probe is NOT an ISE, those are separate probes.

If the pH probe has been sitting around and dry for longer than a few months, then it’s likely shot. Get a new one.
 
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rodpp

Member
Apr 10, 2019
10
Brazil
Yes, the pH electrode was dry. I tried to calibrate it using pH buffers, after leaving it in a KCl solution overnight, without success.

I must buy a new one. As you said that almost all pools have high ionic strength water, I'll buy the regular (less expensive) one.

Regarding the others parameters, I'll forget and use the meter only to measure the pH.

Thank you very much, I appreciate your help!
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,864
Tucson, AZ
Another question, does the "low ionic strength" pH electrode correctly work on the high ionic strength pool water?
Normally one needs to use special pH buffers to calibrate a low ionic strength electrode. The pH reading might not be accurate if you use a LIS electrode. Normally we’re talking about errors in the range of +/-0.1 pH units so it’s not huge but you’ll definitely get an inaccurate reading.

A standard pH probe with high ionic strength calibrating solutions should be used for pool water.
 
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