Chapter4 ConnectingSignals
NI6013/6014 User Man ual 4-40 ni.com
The OUT output timing parameters arereferenced to the signal at the
SOURCE input or to one of the internally generated clock signals on
the NI 6013/6014. Figure 4-35 showst he OUT signal referenced to the
risingedge of asource signal. Any OUT signal state changes o ccur within
80 ns after the rising or falling edge of the source signal.

FREQ_OUT Signal

This signal is available only as an output on the FREQ_OUT pin. The
device frequency generator outputs the FREQ_OUT pin. The frequency
generator is a 4-bit counter that can divide its input clock by the numbers
1 through 16. The input clock of the frequency generator is
software-selectablefrom the internal 10 MHz and 100 kHz timebases.
The outputpolarity is software-selectable. This output is set to
high-impedance at startup.
Field Wiring Considerations
Environmentalnoise can seriously affect the accuracy of measurements
made with the device if you do not take proper care when running signal
wiresb etween signalsources and the device. The following
recommendationsapply mainly to AI signal routing to the device, although
they also apply to signal routing in general.
Minimizenoise pickup and maximize measurement accuracy by taking the
followingprecautions:
•Use differentialAI connections to reject co mmon-mode noise.
•Use individuallyshielded, twisted -pair wires toc onnect AI signals to
thedevice. With this type of wire, the signals attached to the CH+ and
CH–inputs are twisted together and then covered with a shield. You
thenco nnect this shield only at one point to the signal source ground.
Thiskind of connection is required for signals traveling through areas
with largemagneti c fieldsor high electromagnetic interference.
•Routesignals to the devicecarefully. Keep cabling away from noise
sources. The most common noise source in a computer-based DAQ
system is the video monitor.Separate the m onitor from the analog
signalsas much as possible.
•Separate devicesignal l ines from high-current or high-voltage lines.
Theselines can induce currents in or voltages on the device signal lines
ifthey run in parallel paths at a close distance. To reduce the magnetic
couplingbetween lines, separate them by a reasonable distance if they
run inparallel, or run the lines at right angles to each other.