Tilt & Tip Mercury Switches Tilt switches are used to sense movement (tilt) of a device above and below a horizontal axis. A typical use is in a thermostat. A glass mercury switch is mounted to a bi-metallic spring which expands and contracts with temperature.
As the spring moves, the switch contacts pass through the horizontal plane, opening or closing to operate the furnace or boiler. The angle through which the switch must move for proper operation – the differential angle – is measured from the point of just make to just break; it is specified as a maximum.
When selecting a tilt switch, it is important to ensure that the operating mechanism can move the switch through an angle greater than the differential angle. Some additional applications include: level controls, appliances, security alarm systems, toys and games, float switches and water-treatment equipment (non-mercury).
Tip-over switches, sense tilt over 360° of a vertical axis. A common use is in portable heaters used in the home to prevent electrical shock or fire. When the heater tilts more than a specified angle, the switch operates turning the heater off.
This angle, called the operating angle, describes the angle from vertical to the point of contact operation, subject to a tolerance, ie. 45° ± 10° (35° to 55°). Both normally closed (tilt to open) and normally open (tilt to close) switches are available. Some additional applications include: portable lamps, PC anti-theft devices, vending-machine alarms and machinery security systems.