Re: Stupid Question

Marque Crozman <marquec at gastech_com.au> wrote:

>Yes you have done the calibration correctly. The reference electrode in a
pH probe is
>referenced to 7pH. When the probe is placed into a solution of 7 pH, the
output of the
>probe is 0mV. The electronics have then to be calibrated for zero. I
cannot exactly 
>remember what the change in output of the sensor with pH but at 10 pH, the
sensor is
>reading a negative voltage. Setting the slope is then carried out at this

Thanks Marque!  I appreciate it -- it had looked right, but I figured I'd
best make sure :-)

>It has been suggested to me be a manufacturer of pH probes in Aussie, that
an effective
>method for cleaning pH probes is to use pH neutral hair conditioner and a
non abrasive
>cloth, and then to soak the electrode in either a pH buffer solution close
to the pH you
>wish to measure or a 0.1 molar strength KOH solution or to use distiller

>To regouvenate older probes, soaking them for 12 hours in the solution to
be tested,
>ie to aclimatise them, will help to reduce the insidence of eroneous

That sounds like a good idea.  I'm afraid this time out I just cleaned the
probe with a soft, damp paper towel.  I was surprised to find very little
noticable build-up on the surface of the probe, after about 9 months of
sitting in my sump.  Due to some other issues, I'd not been running the C02
injection for the past six months or so, so I'd just left the probe in the
sump to avoid drying out, etc. (and because I didn't get around to putting
it back in its shipping-bottle).

- Chuck