On 10/03/2014 06:03 PM, Alan Faulkner wrote:
Thanks John. I wonder if the calibration would be an
issue with the electronic one?
The strips are cheap but sometimes very difficult to read
and this makes them a very rough indicator.
Also one of them (the third down) does not include the
batteries.
(snip)
Digital pH meter pens gave come way down in price since
I bought one a decade ago. for example:
http://www.ebay.com/itm/221550766554
http://www.ebay.com/itm/111419587528
http://www.ebay.com/itm/141364077523
http://www.ebay.com/itm/191251467428
But pH paper is cheap, too.
http://www.ebay.com/itm/160-Full-Range-pH-1-14-Test-Testing-Indicator-Paper-Litmus-Strips-Kit-Universal-/201070668843
http://www.ebay.com/itm/pH-Strips-1-12-range-vial-100-strips-Test-Paper-Litmus-Pool-Acid-Base-/271226943693
They
sell buffer calibration solutions and salt packets you
dissolve in distilled water, to check and adjust the
calibration. I think the second one, above comes with two
buffer packets. Replacements are cheap and plentiful.
Buffers are solutions that hold a fixed pH value, in spite
of considerable contamination.
Probably the worst thing to use to check calibration is very
pure water, since its pH can be shifted by dipping the tip
of your finger in it. It is the opposite of a buffer.
The batteries they use are very common types. that are very
cheap. The EC meters use these, and I think some of the pH
meters do, too.
http://www.ebay.com/itm/AG13-LR44-LR1154-SR44-A76-357A-303-357-Alkaline-Coin-Cell-Button-Battery-AE-/111433131955
--
Regards,
John Popelish
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