Which relay uses mercury?
A mercury relay (mercury displacement relay, mercury contactor) is a relay that uses mercury as the switching element. They are used as high-current switches or contactors, where contact erosion from constant cycling would be a problem for conventional relay contacts.
How do you test a mercury relay?
Touch the probes to the two leads when you put your multimeter into continuity-test mode. The angle at which the switch opens and closes is determined by tilt. The switch is not continuity when pointing down.
What is a polarized relay?
Polarized relays use the magnetic flux of the permanent magnet in their electromagnetic sections. As the name indicates, these relays have contacts and use an electromagnetic operation to mechanically open and close these contacts to transmit and cut signals, current, or voltage.
How do reed relays work?
A reed relay is a type of relay that uses an electromagnet to control one or more reed switches. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Sealed in a long, narrow glass tube, the contacts are protected from corrosion.
Are mercury switches illegal?
In 2001, California passed a law called SB 633. This law: makes it illegal to sell certain items that contain mercury, encourages people who dismantle, recycle and repair vehicles to remove mercury switches, and.
How much mercury is in a switch?
Amount of Mercury in Switches & Relays A mercury tilt switch, for example, can have anywhere from 50 milligrams to nearly 5 grams (5,000 milligrams) of mercury, while an individual float switch may contain anywhere from 100 milligrams to 67 grams (67,000 milligrams) of mercury.
Why does the coil have no polarity?
Most coils with lead wires use the same color wire for both terminals and have no polarity markings. The answer is that polarity does not matter. You can connect the positive terminal to either of the two wires without affecting the operation of the valve.
Which relay is sensitive to current polarity?
Polarized relays use a permanent magnet. Latching relays tend to be polarity sensitive, and have rather specific drive requirements.
Where is a reed switch used?
Reed switches are used in fluid level sensors for brake fluid reservoirs and to monitor motor oil levels. They are also used in speed sensors for engine control and power steering. Automatic door locks, air bags, parking brakes, seat, door, and hood proximity sensors also utilize reed switches.
What is the difference between relay and reed relay?
A relay switch is composed of an electromagnet that actuates a high power switch made of two metallic contacts. A reed switch is composed only by the contacts themselves that triggers the conduction in the secondary circuit.
How does a mercury wetted contact relay work?
Mercury-wetted contact relays consist of glass-encapsulated reed with its base immersed in a pool of mercury and the other end capable of moving between one or two stationary contact. The mercury films are reestablished at each contact closure and contact erosion is eliminated.
Is the mercury relay a high speed device?
Owing to the mass of mercury moved during switching, compared to that of the armature and spring leaves of a conventional relay, the mercury relay is not a high-speed device. Despite this, the mercury relay does have a very low contact bounce time, in the sub-millisecond range.
Why is mercury relay used for inductive loads?
Despite this, the mercury relay does have a very low contact bounce time, in the sub-millisecond range. For some applications, particularly inductive loads, this alone may be a reason for their use – the timing of contact closure is not rapid, but the avoidance of bounce is valuable. For high-speed use, the mercury-wetted relay is used instead.
What kind of relay is used for high speed?
For high-speed use, the mercury-wetted relay is used instead. This combines the speed of a low-mass relay, together with the fast wetting of mercury contacts. A relay, usually a reed relay, has its contacts coated with a small quantity of mercury.
