The OP8320-1 can be installed on a DB37 cable connected to analog output signals coming from the OPAL-RT simulator. It gives users the option to add custom filtering or protection to these signals.

Each channel can be individually configured using onboard sockets depending on the conditioning required:

• Limitation: signal protection is achieved by using Zener diodes to limit the signal voltage amplitude
• Filtering: snubber filter is adjusted using resistors and capacitors

Signal Protection

To limit the maximum voltage (clipping) of an analog output signal, simply install two Zener diodes Dz1 and Dz2 as shown below in the two sockets represented by a resistor on the PCB and labeled C and R in the figure below.

The limit is calculated using the following formula: Vmax = Vz2 (reverse) + Vz1 (forward)

The following image illustrates how the voltage will be clipped:

Snubber Filter

Use a snubber (a serial resistor R1 and capacitor C1 circuit connected to the GND) to minimize ringing and over/undershoot. Install the capacitor in the C socket and the resistor in the R socket as shown below.

Snubber value depends on the length of the cable and should be used as close as possible to the user unit under test.

The recommended starting RC value is: R=10Ω & C = 1000pF.  Some tuning may be required, depending on application parameters.