Metrix electronic switch utilizes a solid state crystal accelerometer which provides an electrical output when it is deformed by the vibration forces. The output is electronically converted to a signal proportional to velocity. This signal is compared with a preset limit and triggers a solid state relay if the limit is exceeded. There are no moving parts in the 440 vibration switches except when configured with mechanical relays.
While the 440 costs more than a mechanical switch, it uses the same technology as sophisticated remote monitoring systems and provides most of the capabilities of these systems at 1/3 to 1/2 the cost per monitor point.
An important feature of the switche is the built-in time delay. This prevents triggering of the alarm or shutdown functions from transient increases in vibration levels. It also avoids shutdown due to transitory vibrations occurring during start-up.
Almost all machines experience a few seconds of high vibration during start-up before reaching operating speed. When no time delay function is included, as with mechanical switches, this start-up vibration causes a trip. Frequently, the operator turns the trip setting up until he can get through start-up. The resultant trip level is too high to afford protection at the machine’s operating speed.
Three-second alarm trip delay is standard on the switch. Alarm time delays are independently adjustable in the field over a range of 2 to 15 seconds.