Chapter 3
Connecting the Signals
©
National Instruments Corporation
3-9
DAQPad-MIO-16XE-50 User Manual
Figure 3-2.
DAQPad-MIO-16XE-50 PGIA
The PGIA applies gain and common-mode voltage rejection and
presents high-input impedance to the AI signals connected to the
DAQPad-MIO-16XE-50. Signals are routed to the positive and negative
inputs of the PGIA through input multiplexers on the board. The PGIA
converts two input signals to a signal that is the difference between the
two input signals multiplied by the gain setting of the amplifier.
The amplifier output voltage is referenced to the ground for the board.
The DAQPad-MIO-16XE-50 A/D converter (ADC) measures this output
voltage when it performs A/D conversions.
You must reference all signals to ground either at the source device or at the
board. If you have a floating source, you should reference the signal to
ground by using the RSE input mode or the DIFF input configuration with
bias resistors (Refer to the
Differential Connections for Nonreferenced or
section later in this chapter.) If you have a
grounded source, you should not reference the signal to AIGND. You
can avoid this reference by using DIFF or NRSE input configurations.
Types of Signal Sources
When configuring the input channels and making signal connections,
you must first determine whether the signal sources are floating or
ground-referenced. The following sections describe these two types
of signals.
+
+
–
–
PGIA
V
m
= [V
in+
– V
in–
]* Gain
V
in+
V
in–
V
m
Programmable
Gain
Instrumentation
Amplifier
Measured
Voltage
