National Instruments NI 6120 - Manual (Page 29)

Chapter 3 Hardware Overview
© National Instruments Corporation 3-5 NI 6115/6120 User Manual
Analog Output
The NI 6115/6120 supplies two channels of AO voltage at the I/O
connector. The range is fixed at bipolar ±10 V.
The AO channels on the NI 6115 contain 12-bit DACs that are capable of
4 MS/s for one channel or 2.5 MS/s for each of two channels. The NI 6120
DACs are 16-bit, and they have the same AO capabilities as the NI 6115.
Refer to Appendix A,
Specifications , for more detailed information about
the AO capabilities of the NI 6115/6120.
Note The AO channels do not have analog or digital filtering hardware and do produce
images in the frequency domain related to the update rate.
The NI 6115/6120 includes high-density memory modules allowing for
long waveform generations.
Analog Trigger
In addition to supporting internal software triggering and external digital
triggering to initiate a DAQ sequence, these devices also support analog
hardware triggering. You can configure the analog trigger circuitry to
accept either a direct analog input from the PFI0/TRIG1 pin on the
I/O connector or a post-gain signal from the output of the PGIA on any of
the channels, as shown in Figure 3-3. The trigger-level range for the direct
analog channel is ±10 V with a resolution of 78 mV for the NI 6115 and
4.88 mV for the NI 6120. The input impedance for the direct analog
channel is 10 k
Ω. When this direct analog channel is configured for AC
coupling, the corner frequency is 159 Hz.
The range for the post-PGIA trigger from a selected channel is the
full-scale range of the selected channel with a resolution of that range
divided by 256 for the NI 6115 and 4,096 for the NI 6120.
Two trigger reference signals, lowValue and highValue, can then be
independently set to achieve advanced triggering modes. Refer to
Figures 3-3 through 3-8 for illustrations of these modes.
Note The PFI0/TRIG1 pin is an analog input when configured as an analog trigger.
Therefore, it is susceptible to crosstalk from adjacent pins, which can result in false
triggering when the pin is left unconnected. To avoid false triggering, make sure the
PFI0/TRIG1 pin is connected to a low-impedance signal source (less than 1 k
Ω source
impedance) if you plan to enable this input using software.