NI 5442
Output Impedance

The NI 5442 Analog Output path is designed for an output impedance of 50 Ω from the Output Enable relay relative to the main DAC. A selectable 25 Ω resistance can be switched into the Analog Output path between the Output Enable relay and the CH 0 SMB connector for applications such as video testing that require a 75 Ω impedance. Refer to the following figure for more information about the operation and location of the output of the Output Enable relay.

Legend

If the load impedance is high (~1 MΩ), you may see output levels up to twice the selected output value for a matched input/output impedance. These levels can be as high as 4 V_pk-pk for the Main path. Normally, the output levels increase as the load impedance increases. The NI 5442 can compensate for different load impedance values. Refer to CH 0 Connector for more information on the output at the CH 0 connector.

You can select an output impedance of 50 or 75 Ω. Refer to the niFgen Configure Output Impedance VI or the niFgen_ConfigureOutputImpedance function for more information about setting the output impedance.

Note The NI 5442 uses mechanical relays to switch between the 50 and 75 Ω output impedance states. When you change a setting that causes a relay to switch, electromechanical relay bouncing on the NI 5442 interrupts the output signal for up to 10 ms.