Special applications

1. ImpulsingAs the contacting medium is a fluid, the mercury switch lends itself to the impulsing either each way of tilt, or one way only ie no pulse on return. One or more pulses can be supplied in a single tube and the period can be varied within wide limits by the angle of tilt, length of tube etc.

2. Time delay
The same principle that makes impulsing possible also provides a consistent and reliable method of providing delay-make and delay-break actions, either singly or together in one tube. Also, one tube can be supplied to provide many contacts to be switched in at pre-determined time intervals to each other.

3. Silent switching
Mercury switches are silent in action and are well suited to hospitals, churches and anywhere a silent function is required.

4. Level and angle control
The level or any angle can be maintained easily by mounting a mercury switch in such a way that any deviation from the desired position will bring the restoring mechanism into operation until the contacts are separated.

Selection of switches
Mercury switches can handle heavier loads and greater surges without contact deterioration than can metal contactors which break in air. They can also operate with a much higher temperature rise than conventional switching devices.
For inductive loads such as motors and transformers, it should be remembered that the peak value of the current on switching "on" may be from five to 10 times the final load figure and a larger size switch must be selected according to prevailing special conditions of use. For such applications, a switch with a porcelain liner must be used.

The fused-in liner type mercury switch consists of a conventionally shaped tube with bottom or top entry connections. Between the electrodes, a porcelain liner is sealed into the glass tube, becoming one with the glass wall. Such construction adds very considerably to the general mechanical strength of the switch and gives complete arc protection. These switches will withstand 100 per cent momentary overload and surge currents of many times their normal rating without risk of damage.

Unlined glass switches are intended only for use on non-inductive AC circuits for voltages not exceeding 250 volts, and similar DC circuit voltages not to exceed 50. Never use a plain glass unprotected switch on full line voltage DC. When a very rapid operation is anticipated, choose a switch of ample size and a large cooling area. The following are the lengths of standard leads fitted to mercury switches, unless specified otherwise.

1 - 10 amp - 150mm (6")
15 - 60 amp - 230mm (9")
For larger switches details are available on application.

All switches may be fitted with the following leads and insulating materials:

• Plain copper
• Plain copper, covered with single viscose rayon
• Plain copper, covered with double viscose rayon
• Plain copper, covered with silicone rubber
• Tinned copper, covered with PVC

Terminal tags are fitted only if specified.

Listed below are some of the standard flexible plain copper cords available and their current ratings. Unless instructed otherwise, we will select the lead most suitable for a particular rating.

• 60/002 up to 5amps
• 80/002 up to 6amps
• 3/50/002 up to 10amps
• 4/80/002 up to 13amps
• 7/69/002 up to 15amps
• 3/7/002 up to 30amps
• 4/7/60/002 up to 40amps