coagulometer

from The Century Dictionary.

• noun An apparatus in the form of a graduated tube, used to determine the rapidity of coagulation of any given specimen of blood, or the coagulating power of any substance when added to a definite quantity of blood.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun medicine A device used to measure the ability of the blood to coagulate (and the time taken to do so)