Справочник Пользователя для National Instruments NI PCI-6111

The NI PCI-6110/6111 channels are configured as pseudodifferential 
inputs. The input signal of each channel, ACH<0..3>+, is tied to the 
positive input of the PGIA, and each reference signal ACH<0..3>–, is tied 
to the negative input of the PGIA. The inputs are differential only in the 
sense that ground loops are broken. The reference signal, ACH<0..3>–, is 
not intended to carry signals of interest but only to provide a DC reference 
point for ACH<0..3>+ that may be different from ground.

Pseudodifferential signal connections reduce noise pickup and increase 
common-mode noise rejection. This connection type also allows input 
signals to float within the common-mode limits of the PGIA.

Exceeding the differential and common-mode input ranges distorts the input 

signals. Exceeding the maximum input voltage rating can damage the device and the 
computer. NI is not liable for any damage resulting from such signal connections. 
The maximum input voltage ratings are listed in the Protection column of Table 4-3.

You can use the PGIA in different ways when using different input 
configurations. Figure 4-3 shows a diagram of the PGIA.

Figure 4-3.  NI PCI-6110/6111 PGIA

V

m

 = [V

in+

 – V

in–

] 

× Gain

+

+

  PGIA

V

in+

V

in–

–

–

Measured

Voltage

V

m

Instrumentation

Amplifier