i've got two. One snap on one about £80 calibrated so very accurate and one Tenma one not sure on the price or accuracy of this one. Both originally for work purposes but wife stole the snapon one off me for the vivs. :2thumb:
Yer if you're looking for one of these try and get a medical grade one, i got mine for about 30 quid on amazon. Apparently there is a sell by date (probably something to do with the calibration methods), so when medical ones get past it they are sold off very cheaply, i would appear to be incredibly accurate, ive had mine a few years and it worked for calibrating an incubator well enough to hatch a few eggs :whistling2:lol.