stroboscopic tachometer

stroboscopic tachometer

[¦sträb·ə¦skäp·ik tə′käm·əd·ər]
(engineering)
A stroboscope having a scale that reads in flashes per minute or in revolutions per minute; the speed of a rotating device is measured by directing the stroboscopic lamp on the device, adjusting the flashing rate until the device appears to be stationary, then reading the speed directly on the scale of the instrument.