It is a matter of economics really. they all work. some longer than others. If it is in your budget it will be OK.
I use milwaukee sm-301 EC, and ph pen, I have a small 0-999ppm hanna for veggies. bought off ebay by mistake. Now with the new hydrofarm it is great for the lettuce which never gets more than 800ppm. moral of the story. mkae sure the pen reads up to 1999ppm Goodluck Peace.
latewood Reviewed by latewood on . Hanna PH/TDS meters Does anyone know if this PH meter eBay: HANNA HI99104 Pocket pH Tester/Meter/Checker, HI 99104 (item 280087502151 end time Mar-04-07 22:32:47 PST) and this TDS meter eBay: HANNA Primo TDS Meter, PPM Tester, Conductivity (item 280089627902 end time Mar-08-07 11:44:15 PST) are any good? Rating: 5