Reed tachometers

Strobe light A modem tachometer used to measure rpm of rotating equipment. Old-style tachometers measured speed by measuring vibration frequency. They are called reed tachometers. 

When microelectronics and solid state devices developed over the last five to four decades, the development of solid-state sensors followed suit, resulting in the introduction of NTC and PTC resistors to monitor temperature, and first Reed relais and inductive sensors to determine position and distance, or tachometers for rotational measurements in washing machines and dish washers over the past two decades. 

POWER CYLINDERS [H rj WET LINED Cj dry 1 1 UNLINED ELECT. 1 TACHOMETER RAI ENCL. mge MECH. [ 1 VIBR. REED ... 

The speed of a centrifuge should be checked at least once every 3 months. The procedure should use a stroboscopic light or a vibrating-reed external tachometer of known accuracy. The measured speed should not differ by more than 5% from the rated speed under specified conditions. All the speeds at which the centrifuge is commonly operated should be checked. The centrifuge timer should be checked weekly against a reference timer (such as a stopwatch) and should not be more than 10% in error. Commutators and brushes should be checked at least every 3 months. Brushes (where used) should be replaced when they show considerable wear. However, in many modern induction-drive motors, brushes have been eliminated thus removing a source of dust that can cause motor failure. 

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