Different Types of Isolation: Channel-to-Channel, Bank (Channel-to-Bus), and Channel-to-Earth Ground Isolation
Hardware: Compact FieldPoint, CompactDAQ, CompactRIO, Digital I/O (DIO), Instrument Connectivity Other>>Ethernet, Modular Instruments, Multifunction DAQ (MIO), PXI/CompactPCI, SCC
Problem: What are the differences between the types of electrical isolation NI offers on devices? I do not understand the differences between channel-to-channel, bank (channel-to-bus), and channel-to-earth ground isolation.
Solution: Isolation is the separation of physical and electrical components of two parts of the device.
- Channel-to-Earth Ground Isolation
Isolation in-between the device's channels and the device's earth ground. Channel-to-earth isolation is represented in the figure below as |Va - Vd|, |Vb - Vd|, and |Vc - Vd|. This is the most fundamental type and is also included in bank and channel-to-channel isolation. Normally, this isolation type is present on NI 9000 series modules and some SCC modules.
Figure 1. Schematic of Channel-to-Earth and Bank Isolation.
- Bank (Channel-to-Bus) Isolation
Isolation where groups of channels have separate ground planes from each other and the earth ground of the device. In Figure 1, |Va - Ve|, |Vb - Ve|, and |Vc - Ve| represents channel-to-bus isolation.
- Channel-to-Channel Isolation
Each channel is isolated from every other channel and other non-isolated components. In the figure below, |Va, Vb - Vc, Vd|, |Va, Vb - Ve, Vf|, and |Vc, Vd - Ve, Vf| specifically represents channel-to-channel isolation.
Figure 2. Schematic of Channel-to-Channel Isolation.
Note: If the device has a channel-to-channel specification and has AI, AO, and DI/O, such as the NI 6154, the DI/O channels are bank isolated from the other channel-to-channel isolated AI and AO channels.
Related Links: KnowledgeBase 1RL9K2US: What is the Difference between Overvoltage Protection, Isolation, and Safety Isolation (Working Voltage)?Developer Zone Tutorial: High Voltage Measurments and IsolationDeveloper Zone Tutorial: Isolation Technologies for Reliable Industrial Measurements
Attachments: 
ChantoEarthandBankIsolation.JPGChantoChanIsolation.JPG
Report Date: 01/21/2008
Last Updated: 01/25/2008
Document ID: 4HKFIMGP
