How Does Offset Nulling in DAQmx work for the SCXI-1520 and the NI 9237?Primary Software: Driver Software>>NI-DAQmxPrimary Software Version: 8.0 Primary Software Fixed Version: N/A Secondary Software: N/A Hardware: CompactDAQ>>Analog Input Modules>>NI 9237, CompactDAQ>>Analog Input Modules>>NI 9237, SCXI>>Modules>>SCXI-1520
Problem: What is offset nulling and how is it different between the SCXI-1520 and the NI 9237? Solution: SCXI-1520: The SCXI-1520 has an internal hardware offset nulling circuitry that is used to null out the initial bridge offset. When using very large gains on the SCXI-1520, this hardware nulling circuity is valuable because it prevents small offsets from saturating the input circuit, and allows you to maximize the full input range. The nulling circuitry consists of a course potentiometer and a fine potentiometer; the coarse potentiometer is adjusted first, and then the fine potentiometer is adjusted until the reading is nearly 0. If there is still a voltage offset it can be stored in the Initial Bridge Voltage property, allowing DAQmx to subtract this value out before applying any scales.  For more information about the SCXI-1520 nulling circuitry, refer to the user manual. NI 9237: The NI 9237 does not have an internal hardware nulling circuitry because its input range is sufficiently wide so that the inputs will not saturate even with a very large initial bridge offset. When an offset null is performed in DAQmx, the entire offset is stored in the Initial Bridge Voltage property. Related Links: Product Manuals: SCXI-1520 User Manual (Sept 2005) Attachments: IBO_larger.png
Report Date: 04/14/2008 Last Updated: 11/06/2008 Document ID: 4KDENTGP |
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