2.4 Analog Input Signal Connection
The PCI-1202/1602/1800/1802 can measure single-ended or differential type analog input
signal. Some analog signal can be measured in single-end or differential mode, but some
analog signal only can be measured in one of the single-ended or differential mode. The user
must decide which mode is suitable for measurement.
In general, there are 4 different analog signal connection methods as shown in Figure 2-4
to Figure 2-7. The Figure 2-4 is suitable for grounding source analog input signals. The Figure
2-5 is used to measure more channels than in the Figure 2-4 but only suitable for large analog
input signals. The Figure 2-6 is suitable for thermocouple and the Figure 2-7 is suitable for
floating source analog input signals.
Note : In Figure 2-6, the maximum common mode
voltage between the analog input source and the AGND is 70 V
p-p
, so the user must take
care that the input signal is under specification first. If the common mode voltage is over
70 V
p-p
, the input multiplexer will be damaged forever.
The simple way to select the input signal connection configuration is as below.
1.
Grounding source input signal
Æ
select Figure 2-4
2.
Thermocouple input signal
Æ
select Figure 2-6
3.
Floating source input signal
Æ
select Figure 2-7
4.
If Vin > 0.1 V and gain<=10 and need more channels
Æ
select Figure 2-5
If the user can not make sure the characteristic of input signal, the test steps are given as below:
1.
Step1 : try Figure 2-4 and record the measurement result
2.
Step2 : try Figure 2-7 and record the measurement result
3.
Step3 : try Figure 2-5 and record the measurement result
4.
Compare the measurement result of step1,step2,step3 and select
the best one
PCI-1202/1602/1800/1802 Hardware User’s Manual
(Ver. 4.2, Dec/2009, PMH-014-42)---- 25
