NI 5442
CH 0 Connector

The CH 0 connector is the analog waveform output terminal. The maximum output levels from this connector depend on the type of load termination. For example, if the module terminates into a 50 Ω load, the maximum output levels are ±1 V, while the maximum output levels are ±2 V when the module terminates into a high-impedance load (HiZ). This difference is illustrated in the following figure.

If the output terminates into any other load, the levels are defined by the following formula:

V_out = ± [ R_L / ( R_L + R_O ) ] × 2 V

where

V_out is the maximum peak output voltage level

R_L is the load impedance in ohms

R_O is the output impedance of the module in ohms

Note  For loads less than 50 Ω, load impedance compensation supports only combinations of gain and load impedance that meet the previous Vout equation.

By default, R_O = 50 Ω, but you can set the output impedance to 75 Ω in NI-FGEN. Refer to the niFgen Configure Output Impedance VI or the niFgen_ConfigureOutputImpedance function for more information about configuring the output impedance.

You can set the amplitude of the generated output signal in terms of peak voltage by setting the gain value. NI-FGEN calculates and sets the correct amount of attenuation required for the desired gain value. Refer to the Arbitrary Waveform Gain or Amplitude properties, or the NIFGEN_ATTR_ARB_GAIN or NIFGEN_ATTR_FUNC_AMPLITUDE attributes for more information about configuring the output signal amplitude.

Load Impedance Compensation

The NI 5442 has the ability to configure the output signal amplitude based on a user-configured load impedance setting. This capability is desirable when you use the NI 5442 with loads that are between 0 Ω and a high impedance. Refer to the device specifications for information about the output impedance tolerance.

By default, NI-FGEN assumes that the load impedance is equal to the output impedance. If they do not match, you can change the load impedance value that NI-FGEN uses in its load impedance compensation algorithm. NI-FGEN takes the load impedance into account when setting the amplitude and provides the amplitude specified in the configured gain setting, eliminating the use of the voltage divider equation. NI-FGEN compensates to give the desired peak-to-peak voltage amplitude or arbitrary gain (relative to 1 V). Refer to the Load Impedance property or NIFGEN_ATTR_LOAD_IMPEDANCE attribute for more information about load impedance.

Note  The voltage output levels are set in the software and are based upon a 50 Ω load termination (the default), or based on the user–specified load resistance.

For specifications about the waveform output signal, refer to the device specifications.