ICP DAS USA PCI-82x Series, Руководство пользователя

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PCI-82x Series Cards
Multifunction Boards
User Manual, Ver. 1.5, Jan. 2017, PMH-024-15, Page: 16
2.5 Analog Input Signal Connections
PCI-822/826 Series cards can be used to measure either single-ended or differential type Analog
Input signals. Although certain signals can be measured using either mode, other signals, however,
can only be measured in one mode or the other. The most suitable mode for the measurement
must be determined beforehand, and is totally dependent on the prevailing measurement
conditions.
In general, there are four different methods that can be used for connecting Analog Input signals, as
shown below in Figures 2.5-1 to 2.5-5 . The connection method illustrated in Figure 2.5-1 is more
suitable for grounding source Analog Input signals. The connection method depicted in Figure 2.5-3
is used to measure more channels than the method shown in Figure 2.5-1 , but it is only suitable for
large Analog Input signals. The connection method shown in Figure 2.5-4 is suitable for
thermocouple input signals, while the connection method illustrated in Figure 2.5-5 is suitable for
floating source Analog Input signals.
Important Note: For the method illustrated in Figure 2.5-4, the maximum allowable common
mode voltage between the Analog Input source and the AGND pin is 70V
p-p
, so care must be taken to
ensure that the input signal is below this level before continuing. If the common mode voltage is set
to above 70V
p-p
, the input multiplexer will be permanently damaged.
The easiest approach to selecting the most suitable configuration for the input signal connection is
outlined below:
1. Grounding the source input signal

see Figure 2.5-1
2. Thermocouple input signal

see Figure 2.5-4
3. Floating source input signal

see Figure 2.5-5
4. If Vin > 1 V, and the gain is <=10 and more channels are needed

see Figure 2.5-3
5. Current source input signal

see Figure 2.5-6
If the characteristics of the input signal are unknown or unclear, test the signal using the following
procedure to determine the most suitable method:
1. Measure the signal using the connection illustrated in Figure 2.5-1 and record the result
2. Measure the signal using the connection illustrated in Figure 2.5-5 and record the result
3. Measure the signal using the connection illustrated in Figure 2.5-3 and record the result
4. Compare the three results and select the most suitable connection method