Event, State, Count Data Logging – Dry vs. Wet Contacts

In the world of data acquisition, the ability to count events, determining how often those events occurred and when, is a fairly common request. Event, State and Count data loggers like the DI-2160 allow you to do just that. Designed specifically for this purpose, event, state and count data loggers do not acquire signal levels or trends, but simply monitor transitions (e.g. on/off, signal/no signal).

Dry Contacts vs. Wet Contacts

A dry contact is essentially a switch, opening and closing a circuit, without supplying a voltage to that circuit. A wet contact on the other hand, energizes the circuit, providing voltage and allowing current (Amps) to flow through a load (e.g. a fan, lights, solenoids, etc.).

The schematic drawings below illustrate both a dry and wet contact. In the case of the dry contact, you can see that there is no power source engaged when the contact is closed. The contact simply completes the circuit. While the open contact provides isolation, it does not energize anything when closed.

When one of the wet contacts is closed however, it completes a path for current (Amps) to flow, energizing the lamp or motor.

The DI-2160 looks for the presence of a signal (AC or DC), and can count the number of transitions (on/off), record the time and date of each transition, and calculate the total on/off time.

While products like the DI-2160 are great for wet contact applications, where a circuit is energized every time a contact closure occurs, they’re not so great when it comes to dry contact application. In the case of a dry contact closure, there is no signal transition to detect.

Fortunately, DATAQ Instruments does offer a custom solution for just this type of application (i.e. monitoring dry contacts).

If you’re looking to monitor dry contacts, determine when they open/close, how often and for what period of time, call (330) 668-1444 and ask to speak with one of our sales representatives, or email sales@dataq.com.

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