Multi-Tech Systems 7500, 7600 manual Configuring Digital Input, Digital Input Module

ION 7500 / ION 7600 User’s Guide Configuring Digital Input

Configuring Digital Input

Digital inputs are necessary for status monitoring or pulse counting applications. Status monitoring can help you prevent equipment damage, improve maintenance, or track security breaches. Some common status monitoring applications are monitoring the closed/open positions of breakers, on/off status of generators, armed/unarmed conditions in a building alarm system, and over/under pressures of transformers.

NOTE

If you want to confirm the status of a breaker, it should have an auxiliary circuit that indicates whether it is open or closed. If you want to check for the over/under conditions of a transformer, you have to interface the meter’s digital input to a transducer that monitors the transformer and turns on if such a condition exists.

You can also have the digital inputs count transducer pulses to indicate, for example, the number of times a breaker has tripped, or the number of rotations completed by a device. Another option is to have the inputs read pulses from gas, water, steam, or other electricity meters.

Digital Input Module

Digital inputs are used to monitor the status of a sensor such as limit, pressure or temperature switches, and to monitor the status of loads. The source connected to the Digital Input module provides a logic-level signal that describes the state of device that is monitored. The device state is interpreted as either a complete pulse or a KYZ transition (half of a pulse) and is made available as an output. Each state change is determined by the amount of time (debounce time) that the external signal remains in a state.

Digital Input Module Setup Registers

Setup Register	Description
Input Mode	Specifies if the external signal is pulse or KYZ
Event Log Mode	Specifies whether events are logged or not (LOG ON, LOG OFF)
Polarity	Determines if the signal from the hardware is inverting or non-inverting
Debounce	Specifies how long the external signal must remain in a state to be considered
	a valid state change
Port	Defines which hardware port provides the signal

Specifying a Debounce Time

The value specified for the Debounce setup register depends on the kind of signal and the input devices being monitored. A typical value for solid state, dry contacts is 0 to 5 milliseconds. For mechanical dry contacts, a value between 1 and 80 milliseconds is typical. Some input devices may already have a built-in debounce time, often referred to as a Turn On or Turn Off time.

Digital and Analog I/O Technical Note Page 217