User's Manual

Chapter 2 Installing and Configuring the DAQCard-1200

DAQCard-1200 User Manual 2-4 ni.com

Analog Input Polarity

You can configure the AI setting on the DAQCard-1200 for either a

unipolar range (0 to 10 V) or a bipolar range (–5to+5V).Ifyouselecta

bipolar range, the two’s complement coding mode is selected. In this

mode, –5 V input corresponds to F800 hex (–2,048decimal)and+5V

corresponds to 7FF hex (2,047 decimal). If you select a unipolar mode, the

straight binary coding is selected. In this mode, 0 V input corresponds to

0 hex, and +10 V corresponds to FFF hex (4,095 decimal).

Analog Input Mode

The DAQCard-1200 has three input modes—RSE, NRSE, and DIFF. The

single-ended modes, RSE and NRSE, provide eight input channels. DIFF

input mode provides four input channels. Table 2-2 describes these modes.

While reading the following paragraphs, you may find it helpful to refer

to the Connecting Analog Input Signals section of Chapter 3, Connecting

the Signals, which contains diagrams showing the signal paths for the three

modes. These three modes are software-selectable.

DIFF Input Mode (Four Channels)

DIFF input mode means that each input signal has its own reference, and

the difference between each signal and its reference is measured. The signal

and its reference are each assigned an input channel. With DIFF input

mode, the DAQCard-1200 can monitor four different analog input signals.

Table 2-2. Analog Input Modes for the DAQCard-1200

Analog

Input Modes

Description

DIFF DIFF mode provides four differential inputs with the positive input of the

instrumentation amplifier tied to channels 0, 2, 4, or 6 and the negative input tied

to channels 1, 3, 5, or 7, respectively, thus pairing channels (0, 1), (2, 3), (4, 5),

(6, 7).

RSE RSE mode provides eight single-ended inputs with the negative input of the

instrumentation amplifier referenced to AISENSE/AIGND, which is tied to

ground through about 200 Ω resistance (default setting).

NRSE NRSE mode provides eight single-ended inputs with the negative input of the

instrumentation amplifier tied to AISENSE/AIGND, which is not connected to

ground.