Digital Chlorine Meter

[pratzert]

Hi All.

I use a digital pH meter and it seems to do a decent job.

I have also seen a few Digital Chlorine meters on the web.

Has anyone (BEN?) used one of them? Any good?

I'd like to hear some opinions/comments on them.

Thanks !

[PoolDoc]

Every portable digital 'chlorine meter' I've seen is EITHER totally bogus (units under $20) OR based on ORP electrodes.

Your pH meter actually measure pH, but ORP meters do NOT actually measure chlorine. Instead they measure the NET oxidizing state of the water. That is, they measure all the oxidizers minus all the reducing agents.

This means:

• If you add dichlor (50% chlorine, 50% stabilizer) your ORP may go DOWN, even though the chlorine went UP.
• If you add potassium monopersulfate, your ORP, or indicated chlorine, will go UP, even though there's none in the pool!
• If you have stabilizer AND chlorine in the pool, and the sun gets covered by clouds, your indicated chlorine will increase.
• And more . . .

I have sold and serviced multi-thousand dollar OPR/pH control systems for commercial pools. They can work well on indoor pools. They tend to be a nightmare on outdoor pools, unless you have a staff pool person

(a) who will listen,
(b) has some basic knowledge of science and chemistry, and
(c) has an IQ > 110.

Most pools lack this sort of staff . . . which is why I've found perfectly good $10,000 Stranco pool controllers turned off.

But, there's a market for chlorine meters. And where there's a market, SOMEBODY will sell SOMETHING!

• So stuff like this gets sold: Extech CL500 chlorine meter for $500+.
  Chlorine meter, right? Actually, it's just a DPD colorimetric meter, less accurate than the K2006 and MUCH less dependable!
  
• Or this Yosoo PH Tester Chlorine Level Meter fraudulent unit which has been around for over a decade and is STILL sold. At only $20 it's STILL not bargain!
  
• Or this LaMotte 1740 Total Chlorine Tracer PockeTester for $200+. Not a fraud; just a straight up pH/ORP meter. But not useful, either! See Lamotte's web page.[/INDENT]

There are some claimed 'true' chlorine electrodes, like this Orion Scientific unit:

Orion 9770BNWP Residual Chlorine Ion Selective Electrode . . . for $666.

But I've never had a reason to test one, and I've never seen reliable information on whether they really work, without endless calibration!

So . . . save your money.

[pratzert]

Thanks Ben.

Sounds like I should save my money and stick with the wet agent for testing/measuring free chlorine.

I appreciate the advice.