Decreasing the Source Impedance of an Analog Input SignalHardware: Multifunction DAQ (MIO)
Problem: When scanning through multiple input channels, I am seeing crosstalk or ghosting between my signals. How do I create a buffer to decrease the source impedance of my analog input signal to reduce or eliminate this ghosting? Solution: Source impedances greater than 1 kΩ are not recommended with multiplexed data acquisition devices because they increase the amount of settling time required for an accurate measurement. A unity gain buffer, also called a voltage follower, provides a high input impedance, and a low output impedance. With this buffer, the multiplexer can receive low-impedance signals from high-impedance sources, thus decreasing the time required for settling. A unity gain buffer is implemented with an operational amplifier. For a description and illustrations of how to set up a unity-gain buffer in a data acquisition setup, see section 3 of Developer Zone Tutorial: Using a Unity Gain Buffer (Voltage Follower) with a DAQ Device.There are other methods to eliminate or reduce ghosting. For more information see KnowledgeBase 3L8IETLO: How Do I Eliminate Ghosting From My Measurements? For more information on the implementation, use, and need for unity gain buffers, please refer to the Related Links section below. Related Links: Developer Zone Tutorial: Using a Unity Gain Buffer (Voltage Follower) with a DAQ Device Developer Zone Tutorial: Is Your Data Inaccurate Because of Instrumentation Amplifier Settling Time? KnowledgeBase 3L8IETLO: How Do I Eliminate Ghosting From My Measurements? Wikipedia: Buffer amplifier Attachments:
Report Date: 08/09/2002 Last Updated: 06/24/2008 Document ID: 2O8AD10T |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
