I don't know about the PH part, but Cecil let me use one almost identical to this one
http://www.ysi.com/productsdetail.php?550A-22

Accurate and dependable. Affordable? Well, that depends on your wallet.

But, if you buy one that isn't accurate and dependable, then you're just throwing money away.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
http://www.pondboss.com/subscribe.asp?c=4
3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).