National Instruments PCI-4451 用户手册
Chapter 4
Signal Connections
©
National Instruments Corporation
4-9
PCI-4451/4452 User Manual
Analog Input Signal Connections
The analog input signals for the PCI-4451/4452 devices are +ACH<0..3>,
−
ACH<0..3>, and AIGND. The +ACH<0..1> signals are tied to the two
analog input channels of your PCI-4451, and ±ACH<0..3> are tied to the
four analog input channels of your PCI-4452 device.
four analog input channels of your PCI-4452 device.
Caution
Exceeding the differential and common-mode input ranges distorts your input
signals.
signals.
AIGND is an analog input common signal that connects directly to the
ground system on the PCI-4451/4452 devices. You can use this signal for a
general analog ground tie point to your PCI-4451/4452 device if necessary,
but connecting AIGND to other earth-connected grounds is not
recommended. AIGND is not directly available if you are using a
BNC-2140 accessory.
ground system on the PCI-4451/4452 devices. You can use this signal for a
general analog ground tie point to your PCI-4451/4452 device if necessary,
but connecting AIGND to other earth-connected grounds is not
recommended. AIGND is not directly available if you are using a
BNC-2140 accessory.
Figure 4-3 shows a diagram of your PCI-4451/4452 device analog input
stage.
stage.
Figure 4-3. Analog Input Stage
The analog input stage applies gain and common-mode voltage rejection
and presents high input impedance to the analog input signals connected to
your PCI-4451/4452 device. Signals are routed directly to the positive and
negative inputs of the analog input stage on the device. The analog input
stage 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
and presents high input impedance to the analog input signals connected to
your PCI-4451/4452 device. Signals are routed directly to the positive and
negative inputs of the analog input stage on the device. The analog input
stage 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
!
+ACH
x
-ACH
x
AIGND
Calibration
Multiplexer
Multiplexer
DC/AC
Coupling
20 dB
Attenuator
Analog
Lowpass
Filter
Differential
Amplifier
+
–
Gain = 0 dB
Gain = 10 dB
Gain = 20 dB
Gain = 30 dB
Gain = 40 dB
Gain = 50 dB
Gain = 60 dB
Gain = 10 dB
Gain = 20 dB
Gain = 30 dB
Gain = 40 dB
Gain = 50 dB
Gain = 60 dB
Gain = 0 dB
Gain = -20 dB
Gain = -20 dB
f
c
= 3.4 Hz
1 G
Ω
1 G
Ω
900 k
Ω
100 k
Ω
100 k
Ω
900 k
Ω
0.047 F
0.047 F
A/D
Converter
AIGND
User.book Page 9 Tuesday, April 14, 1998 10:20 AM