Dear Mr Clun,
As per the techical dictionary definition
1.An instrument for measuring the flow of viscous liquids, such as blood (In medical field,an instrument for measuring the velocity of the blood current in the arteries).
2. An instrument for measuring currents, especially the force or intensity of electrical currents; also called as galvanometer.
if you search using any search engine you will get thousands of hits.
regards,
KMP