Internal shunt resistor scaling

Use shunt scaling for applicable eDAQXR layers and MX modules.

Before starting the shunt scaling task, define all pertinent parameters for the bridge configuration, including the Shunt resistor and Shunt polarity.

Note that the % Dev parameter is a read only parameter that is automatically updated after the shunt scaling task is completed. The % Dev is the calculated percent deviation from the ideal shunt span based on the bridge type, bridge resistance, lead wire resistance and shunt resistance. In brief, it provides feedback to the user on the accuracy of the shunt scaling experiment.

NOTE
Shunt polarity is based on electrical units scaling (i.e., mV/V scaling). If the sensor scaling slope is negative, the shunt polarity in output units is in the opposite direction. For example, the Up Scale option would result in a negative swing in the output data.

See Shunt scaling based on a known shunt scaling (Page 1) for information about the shunt tool allowing the user to define a calibration step consisting of the selection of any one of the FCS shunt resistors along with the corresponding equivalent engineering value based on another Known Shunt calibration.

Select the channel or channels to be scaled and click Shunt Scaling.

ClosedScreenshot

When this task starts, the GUI displays some temporary parameter settings in the grid interface. These can be ignored as the user defined settings are restored later. The Units and Physical span values can be modified before or after the Electrical zero and Electrical span are measured.

NOTE
For the MX1615B-R module only, to optimize the scaling accuracy, the CX23-R/eDAQXR automatically uses the AC Excitation mode and the largest Excitation range available during sensor scaling. If necessary, the Excitation mode and range revert to the user-defined values after shunt scaling is completed or canceled. In this situation, the channel requires zeroing and the GUI prompts the user to do this.

Perform shunt scaling in three steps:

  1. Click Zero to record the unshunted values, which are used to set the zero offset.
  2. Click Install to install shunts.
  3. Wait for the installed shunt readings to stabilize, then click Measure to record the shunted values. The recorded unshunted and shunted values are used to define the Electrical zero and Electrical span parameters. After scaling is complete, be sure to save the test setup.

NOTE
It is recommended to select the Use system defined sensor scaling filters option in the System preferences to minimize the effects of noise on the accuracy of scaling measurements.