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What voltage is a dry contact?
Dry contacts are primarily used in low-voltage (less than 50 V) AC distribution circuits. It can also be used to monitor alarms such as fire alarms, burglar alarms and alarms used power systems.
What is no dry contact?
No current: A dry contact is the synonym of volt free — it is not “wetted” by a voltage source. Dry contact can refer to a secondary set of contacts of a relay circuit which does not make or break the primary current being controlled by the relay. Dry contacts means a relay that does not use mercury-wetted contacts.
What is potential free input?
Potential free contacts are also sometimes called volt free or “dry” contacts, and simply refer to relay contacts, or switch or sensor contacts, which haven’t been wetted with voltage by the machine or device in which they exist. It doesn’t refer to some characteristic of the contacts themselves.
What is a wetted input?
Wetted inputs indicate that the power source is integrated into the digital input (i.e., the signal line from the input supplies voltage potential to a dry contact). There are a couple of ways to configure a wetted (also often called sourcing) digital input, as shown in Figure 2 and Figure 3.
Can a dry contact input be a closed circuit?
As long as the cable between the alarm and IO board is relatively short, you should not have any problems. You wrote: “If the digital output relays are close, my dry contacts will become a closed circuit and current will flow because the digital outputs are rated 250VAC/30 VDC, 2A??
Do you need NC output for dry contact control relay?
I would need a NC output on the relay to maintain power to the electronics module until the contact closure occurs on the input to the dry contact control relay. Am I correct that a “dry contact control relay” would accomplish this?
What kind of current do I need for a dry contact?
I don’t want it too high so that a standard open collector output (30V/50mA-100mA) can work on it as well. A dry contact can sometimes require what is known as a wetting current. This means that when the contact closes, a current is available to flow through the contact of a certain amount (usually specified by the vendor).
Can a wet contact control a dry contact?
For example, a relay with a 24 V coil, a dry contact will allow controlling the load at any voltage level. This cannot be achieved by the wet contacts because the wet contacts use the same voltage level to control the load.