What are you using it for?(Testing pool ph or critical lab work.)
You can usually pick one up cheaper than you can build.
Scott Welch or Allen Welch makes a variety from a pocket unit to a
high end table top unit.
Try going over to the Edmund Scientific site they sell them.
(I have a small pen type that is extremely accurate that I use for
testing photo chemicals, also works on my swimming pool. Cost 50.00
| I have a nice pocket pH tester sold by Cole Parmer
My uncle ( a crop biologist ) said pocket ph meters are not
durable, so I bought & use a pack of 100 strips of
Universalindikator pH 0 -14 ( made by Merck, in Germany ) :
work well for colourless fluid, but may be less accurate (
colours displayed will be darkened ) for dark coloured fluid.