PXIe-4300 Terminal Block Effect on Input Impedance

Updated Nov 28, 2018

Reported In

Hardware

  • PXIe-4300
  • TB-4300
  • TB-4300B

Issue Details

I am using the PXIe-4300 and I want to know the effect of using the TB-4300 or the TB-4300B to its input impedance.

Solution

According to the the PXIe-4300 Specifications Manual, the input impedance will be different depending on whether the device is on or off. This is due to protection and signal conditioning circuitry that is only active when the device is on. 

When on, the PXIe-4300 has over 1 GΩ input impedance between AI+ and COM, and between AI- and COM. As shown in Figure 1 below.
 

Figure 1: NI PXIe-4300 Input Impedance with no Terminal Block
 
The TB-4300 is a non attenuating feed-through terminal block. It has no effect on the input impedance of the device, as shown in Figure 2 below.
 
Figure 2: NI PXIe-4300 Input Impedance with TB-4300 Terminal Block

The TB-4300B is an attenuating terminal that has a 1.2 MΩ impedance between the AI+ and AI- pins as shown in Figure 3 below. This terminal block has no effect on the impedance of the NI PXIe-4300 impedance between AI+ and COM or AI- and COM.
 

Figure 3: NI PXIe-4300 Input Impedance with TB-4300B Terminal Block