If you're on a budget, you could try a pH test kit. Here's one, second from the bottom: http://www.genhydro.com/genhydro_US/phcalibration.html I have a kit made by them with the test solution and bottles of pH "up" and "down" that was about $15.00 I think. Sure, a digital is better... but good ones are pretty expensive.
my experience have been bad. bought ones at wal-mart that only goes down to 6.2, and not accurate at all. got a digital meter and readings were totally different. a hanna off of ebay will only run you 25 dollars plus the required buffer sollutions.
You can buy a PH testing kit for around $10 or 5 quid. Its a well worthy investment especially if you are growing hydroponically. Saves your beautiful plant from getting scorched roots etc Check out the following article to learn more about PH and cheap and easy ways of testing. PLease also check out all other grow articles by clicking on the grow guide link at the top of the page. http://www.growingcannabis.co.uk/?q=node/63 Just blaze