Bangalore-based em electronix offers rpm controller. This is a compact and low cost means of monitoring and controlling the speed. Rpm controller has 4 display digits and 3 keys packed in a compact abs plastic panel mountable housing having the front bezel of 72 mm x 72 mm. Specifications: speed: 0000 to 9,999 rpm; accuracy: ±1 count.It uses non-contact sensors such as magnetic or optical proximity switch to sense the speed and actuates the relay whenever the speed exceeds the set limit. The setting of parameters can be done using the soft membrane key provided in the front panel. The contact points of relay can be used for zero speed protection or over speed protection of the drives. An optional 0-l0 v output can also be provided. A sturdy enclosure suitable to ip65 grade is provided. An in-built supply for powering the sensors is provided. The supply voltage options are 230 v +/- 10 percent, 50 hz or 24 v dc.