Best Thermometer?

[**sarahp**]

So I had a tank emergency last week - my Rena tank started to leak and I had to get a replacement fast.  The new one is perspex and I think it holds it's temperature differently to my old glass one.
 
I really need a good thermometer so that I can monitor this until I get used to whats normal.  I have one of those stick on the outside ones but it doesn't seem that great.  I have a glass one inside but the sucker doesn't seem to work that well I have to refix it almost every day which is getting annoying!  So I've been looking at digital ones that have a probe in the water and a reader out of the water.
 
Any suggestions on which type are best and what is a good, reliable but not ridiculously expensive make?

 

[Far_King]

For my digital thermometer needs I use one of these: http/www.amazon.co.uk/Black-Aquarium-Digital-Thermometer-Water/dp/B00931LJW0/ref=sr_1_4?ie=UTF8&qid=1453924928&sr=8-4&keywords=aquarium+thermometer
 
I have the stick on ones too for the "quick glance" but to actually monitor what's going on I can recommend that ^