That pH meter sucks and it doesn't look waterproof. A cheap pH pen is like $50 and that ebay one is $8. Don't expect it to be accurate for very long. Spend some money on a good pH pen, it's worth the peace-of-mind knowing your plants are in the pH zone where they will thrive. I'd suggest Eco Tester PH1: http://www.wormsway.com/detail.aspx?sku=WET500&AC=1 ...it's accurate, stable, easy to calibrate and waterproof.
The radio shack scopes work, but what kind of quality do you expect for $12?
