ET-16DO2 Usage Tips

Driving Inductive Loads with Discrete Outputs

EtherTRAK discrete output modules have clamping diodes to absorb the turn-off transients that often occur when inductive loads turn off.

High Inrush (Startup) Current

Some devices draw several times their steady state current for a brief period when they are first turned ON. EtherTRAK discrete output modules are rated to handle this expected inrush. Since this high current only flows for a short period of time, very little heat is generated in the solid state power switches within the module.

Note about Discrete Output Wiring

All outputs are powered by the same source of power that operates the module. (It is internally connected.) All loads must return to the same ground as the module.

Driving A Heavy Load

To drive a load that exceeds the 1 Amp rating or when using a voltage source other than one operating the module, use an interposing relay or power contactor to transfer the control.

Time Proportioned Outputs

Time proportioned discrete outputs pulse ON and OFF with a duty cycle (ON to OFF ratio) that is proportional to an analog output value assigned to control that output. TPO outputs provide a low cost and high performance method to control heaters and other process variables. Typically the analog output register associated with the TPO is linked to the output of a PID or other control algorithm. Each time proportioned output is cycled ON and OFF quickly to provide smooth control. The maximum ON / OFF time is settable to avoid fluctuations in the process control in accordance with the dynamics of the system. The minimum pulse time is settable for slow reacting power controllers such as mechanical relays and piloted valves.