What is a dry contact?
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What are dry contacts and wet contacts, and how are they defined? Would an authoritative explanation be best?
I’ve only heard of dry contacts; generally, dry contacts refer to the normally open contacts of devices such as contactors and relays
Definition of dry contact: A passive switch； Has two states: closed and open ； There is no polarity between the two contacts, allowing them to be swapped ； Common dry contact signals include: 1. Various switches such as limit switches, travel switches, foot switches, rotary switches, temperature switches, level switches, etc ； 2. Various buttons ； 3. Outputs from various sensors, such as those used in environmental condition monitoring: water intrusion sensors, fire alarm sensors, glass breakage sensors, vibration sensors, smoke sensors, and condensation sensors ； 4. Outputs of relays and reed switches ； Where there are dry contacts, there are also wet contacts. The definition of a wet contact is: an active switch ； It has two states: powered and unpowered ； There is polarity between the two contacts; they cannot be connected in reverse ； Common wet contact signals include: 1. If the above dry contact signals are connected to a power supply, and the other terminal of the power supply is used as the output, then it constitutes a wet contact signal ； In industrial control, the common voltage range for wet contacts is DC0～30V, with DC24V being the more standard value ； The AC110～220V output can also be a wet contact, although this is less common ； 2. It is also acceptable to use the TTL level output as a wet contact ； Under normal circumstances, TTL levels require buffered outputs, such as 7407, 245, 244, etc., which form a circuit with VCC and other components ； 244 and 245 can also form a circuit with gnd ； To drive the optocoupler at a distance. 3. Collector output of the NPN transistor and VCC ； 4. Collector output of the Darlington transistor and VCC ； 5. Outputs of infrared reflectance sensors and through-beam sensors ；
Simply put, a dry contact is a contact that does not provide any voltage output; it is also known as a passive contact.
Simply put, it’s about checking whether the contact is charged or not! 1. The “non-charged” one on the contact is a dry contact ； 2. The part that is “live” on the contact is the wet contact.
Simply put, it’s about checking whether the contact is charged or not! 1. The “non-charged” one on the contact is a dry contact ； 2. The part that is “live” on the contact is the wet contact.
I’m hearing the term “wet contact” for the first time, haha
lou shang zheng jie!
I don’t think there’s such a thing as a wet contact point
Dry contacts refer to those where the instrument wires coming from the field (two wires) carry no voltage, while wet contacts are those that carry voltage
I believe that physical contacts without signals such as current or voltage are dry contacts.