Chapter 7

Analog Output

DACs. It allows you to download the points of a waveform to your M Series device without host computer interaction.

AO Sample Clock

The AO Sample Clock signal reads a sample from the DAC FIFO and generates the AO voltage.

AO Range

The AO Range is ±10 V for NI 621x devices.

Minimizing Glitches on the Output Signal

When you use a DAC to generate a waveform, you may observe glitches on the output signal. These glitches are normal; when a DAC switches from one voltage to another, it produces glitches due to released charges. The largest glitches occur when the most significant bit of the DAC code changes. You can build a lowpass deglitching filter to remove some of these glitches, depending on the frequency and nature of the output signal. Visit ni.com/support for more information about minimizing glitches.

Analog Output Data Generation Methods

When performing an analog output operation, you either can perform software-timed or hardware-timed generations.

Software-Timed Generations

With a software-timed generation, software controls the rate at which data is generated. Software sends a separate command to the hardware to initiate each DAC conversion. In NI-DAQmx, software-timed generations are referred to as on-demand timing. Software-timed generations are also referred to as immediate or static operations. They are typically used for writing a single value out, such as a constant DC voltage.

Hardware-Timed Generations

With a hardware-timed generation, a digital hardware signal controls the rate of the generation. This signal can be generated internally on your device or provided externally.