FIGURE 3
FIGURE 4
&(&,&
in LabVIEW in the DAQ Assistant setup by inverting the
input lines just as you would a digital output line.
Turn The Tables
An AC input module is shown in Photo 5. It has an input
rating from 90 VAC up to 140 VAC on terminals #1 and #2.
Crydom offers other input modules in this AC product line up to
280 VAC. This module also has an open collector output and can
be wired to the USB-6008( 9) digital input terminals as shown
in Figure 4. Just like the DC input module, the AC input module’s
output is inverted from what the user would normally expect
and can be inverted in LabVIEW in the DAQ Assistant setup.
Conclusion
With the help of SSRs and input modules, the USB-
6008( 9) unit can control AC and DC loads and inputs from
AC and non-TTL DC signals. In most cases, low voltage TTL
signals are not used outside of the PC since they are too
low and are susceptible to noise. Also, 5 VDC is not directly
available from batteries and standard wiring systems found
in homes and businesses. Then, there’s always the real
danger of voltage spikes and unsuitable voltage levels
getting back into your interfacing circuit and PC. Next
time, we’ll cover the analog inputs and outputs of the
USB-6008( 9) units. SV
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SERVO 05.2009
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