Generally they are all very similar calibrated for a medium reflective surface and usually with in 2 degrees accuracy.

CHECK THE SPECS before you buy some are 4 degrees up or down and you can get better than that for not too much $$.

If you want better accuracy, look at a science supply but sit down when you do. I just plan that it can be 2 degrees from what you measure. (I use 81 low and 90 high which even 2 degrees [79-83 and 88-92] up or down is still ok)