You can use single-ended measurement systems when all input signals meet the following criteria:

•High-level signals (normally, greater than 1 V)

•Short or properly-shielded cabling/wiring traveling through a noise-free environment (normally, less than 15 ft)

•All signals can share a common reference signal at the source

Use differential connections when your system violates any of the above criteria.

Channel Addressing with the AMUX-64T

An AMUX-64T external multiplexer accessory expands the number of analog input signals a DAQ device can measure. You can attach 1, 2, or 4 AMUX-64T accessories to a DAQ device. The number of AMUX accessories used is set in the device configuration of Measurement & Automation Explorer (Windows) or the NI-DAQ Configuration Utility (Macintosh). Every four channels on the AMUX accessory are multiplexed to one channel on the DAQ device. In LabVIEW, each onboard channel corresponds to four AMUX channels on each AMUX. For example, with one AMUX-64T, the channel string 0:1 acquires data from AMUX channels 0 through 7, and so on. With two AMUX-64T accessories, the channel string 0:1 acquires data from both AMUX accessories channels 0 through 7.

You also can acquire data from a single AMUX-64T channel by using the channel string AMy!x, where x defines the channel number and y defines the number of the desired AMUX (y = 1 if you have just one AMUX configured). For example, AM3!8 returns channel 8 on the third configured AMUX-64T. Refer to the Acquire 1 Pt, 1 Ch via AMUX-64T VI in the examples\daq\anlogin\anlogin.llb for an example of acquiring data from a single AMUX-64T channel.

Important Terms You Should Know

The following are some definitions of common terms and parameters that you should remember when acquiring your data:

•A scan is one acquisition or reading from each channel in your channel string.

•Number of scans to acquire refers to the number of data acquisitions or readings to acquire from each channel in the channel string. Number of samples is the number of data points you want to sample from each channel.