ba--about dry nodes and wet nodes

Knowledge of dry contacts and wet contacts

Popular definition : There is a dry contact with a wet contact, for the switching volume. the definition of wet contact is : active switch, has 2 kinds of state with electricity and no electricity, 2 contacts have polarity, can not reverse connection;

Common Wet contacts

1, if the above dry contact signal, connected to the power supply, and then another pole of the power supply, as the output, is the wet contact signal; Industrial control, commonly used wet contact voltage range is dc0~30v, compared to the standard is dc24v;ac110~ 220V output can also be wet contact, although this is relatively small;

2, the TTL level output as a wet contact, also can not be; In general, the TTL level needs to be buffered output, such as: 7407, 245, 244 and so on, and VCC and other components of the circuit, 244, 245 may also be formed with GND circuit;

Drive a distant optocoupler.

3, the NPN transistor collector output and VCC;

4. The collector output and VCC of the Darlington tube;

5, infrared reflection sensor and the output of the sensor;

Common Dry Contacts

In the field of industrial control, the use of dry contacts is much more than wet contacts, because the dry contacts do not have the advantages of polarity:

1, casually access, reduce engineering costs and engineering personnel requirements, improve the speed of the project

2, the processing of dry contact switch quantity is many

3, connecting the dry contact wire even if long-term short-circuit will not damage the local control equipment, will not damage the remote equipment

4, easy to access, easy to unify the interface

Dry contacts are commonly known, but, in fact, in the field of industrial control, is already a standard noun. Definition of dry Contact: passive switch, 2 states with closure and disconnection, no polarity between 2 contacts, can be interchanged;

Common dry contact signals are:

1, various switches such as: limit switch, stroke switch, foot switch, rotary switch, temperature switch, liquid level switch, etc.

2, various keys;

3, a variety of sensor output, such as: Environmental power monitoring sensors: water immersion sensor, fire alarm sensor, glass crushing, vibration, smoke and condensation sensors;

4, relay, reed tube output;

ba--about dry nodes and wet nodes