Each section below has a color listed in parenthesis that corresponds to its location on the Figurte 3 below.
See the specifications for your load cell to determine the amount of excitation needed. The NI 9237 can provide 2.5 V, 3.3 V, 5 V, or 10 V of excitation. If a different value is selected, then the module will default to the nearest value from the list provided.It is not possible to use a combination of Internal Excitation and External Excitation as there is an internal hardware difference depending on the selection. Note: As stated in the NI 9237 Specifications, linked below, the total maximum power supplied by the NI 9237 is 150 mW. If more power is needed, then use external excitation provided by an another source.This is less of a concern with passive sensors, i.e. strain gauge based sensors, as the change in resistance is measured from stimulation. Verify the power requirements when using sensors that require circuitry to be powered, i.e. TEDS, where under-powering the transducer could cause incorrect readings. For more information about passive transducers, see Knowledge Base: What Determines if a Transducer Is Active or Passive? in the Related Links section below.
For unlisted units, create a Custom Voltage with Excitation task and apply a custom scale as explained in the DAQmx 9.0.2 and Earlier section.
Figure 2: Default scaled unit options
Select Configure Scale to launch the Configure Scale Dialog to customize the scaling parameters. See Knowledge Base: DAQmx Custom Scales in Measurement & Automation Explorer (MAX) for the NI 9237 in the Related Links section below.
When using the internal master timebase of 12.8 MHz, the result is data rates of 50 kS/s, 25 kS/s, 16.67 kS/s, and so on down to 1.613 kS/s, depending on the value of n. See the NI 9237 Operating Instructions and Specifications in the Related Links for more information.
Figure 3: Configuration for a full bridge 350 Ohm transducer using 2.5 V of internal excitation with a range of +/- 100 pounds
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