Multi-channel shunt scaling

Use shunt scaling for applicable eDAQXR/eDAQXR-lite 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.

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/eDAQXR-lite 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.

Click the options menu button to access additional options:

  • Use scientific notation: Select scientific notation for extremely large or small values.
  • Decimals: Select the number of decimal places to show.
  • Update rate: Select the rate at which the display refreshes at 1, 2, 5 or 10 times per second. Note that in cases where the channel sample rate is less than the selected update rate, the display refreshes at the lower sample rate.
  • Control: Open the Shunt control dialog. This is not available for all channel types.

NOTE
For the meter to show accurate readings, the system starts a background test run for the duration of the digital display. No other digital displays or test runs can be started.

NOTE
MX modules output overflow values when no suitable connector is found. This is represented by a series of "+" characters on the display.