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Re: [APD] CO2 and pH control

> Date: Wed, 14 Dec 2005 08:05:26 +0100
> From: "Laith Arif" <laith at swissonline_ch>
> Subject:     To: "'aquatic plants digest'" <aquatic-plants at actwin_com>
> Usual single point calibration is to 7.0, not 7.2.  Dual point calibration
> is usually to 7.0 and either 4.0 or 10.0.
I have a question about the lifetime of my pH probe.  I bought a Milaukee 
SMS 122 probe and controller in September 2002.  I was under the impression 
that I would have to replace the probe after about a year.  But it's been 
three years now, and it seems to be working as well as ever.

Every few months, I check the calibration against Vital Sine pH 7.01 and 
4.01 solutions, and it's never more than 0.1 unit off.  Usually it's right 
on the mark and doesn't need any tweaking.  As long as this is the case, is 
there any reason to replace the probe?  Thanks.

John T. Fitch

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