Their fingers and a watch.
stethoscope
An ECG (Electrocardiography) machine.
This instrument is called a stethoscope.
stethoscopes
A yarn count meter is the instrument that directly measures the yarn count. It calculates the length and weight of the yarn to determine the count, which indicates the thickness or fineness of the yarn.
Generally least count of micrometer varies instrument to instrument.. But common micrometers which are used in institute level laboratories have least count of 0.0001mm
Normally 75-85 beat per min
You can count to ten or focus on slowing your heartbeat down.
Piano
A stethoscope is used to listen to the heart and lungs.
Counting one by one Yarak salak Oruspu Dohh
That sounds quite abnormal to me. My own heartbeat has never interfered with my ability to count.