DC offset problems in NI-5401 function generator card

[Suresh thangappan]

When i give a Dc offset of 1 Volt the output of my function generator reads 1.97v. what is the reason behind this,why is it so what setting have to be made so as to get the dc ofset only when no ac signal is given.

[JerryAL]

Hi. The NI 5401?s output voltage is specified in terms of 50 ohms. This means for a 50 ohm load, you should see 1.0 Volts for a 1.0 Volt setting when the load is 50 ohms. For an other than 50 ohm load, there is a voltage divider action that takes place, where the voltage will vary up to double the size for a high impedance load, such as most default oscilloscope settings. The Connecting Signals>>ARB Connector section of Chapter 1 of the NI 5401 user manual describes this in further detail.

To generate just a DC voltage level, there is an option for DC as the Waveform to use when programming the device. The LabVIEW niFgen Function Generator Example shows this on the front panel. If you are using the Sources Soft Front Panel, when the Standard Function Output is se
lected, there is a DC Voltage level selection button available to be selected to generate a DC voltage.