Use shunt scaling for modules with a shunt resistor.
Before starting the experimental scaling, the Shunt resistor, Shunt polarity and % Dev parameters must be defined. Set the Shunt polarity parameter to Down scale or Up scale. Specify the % Dev to allow the shunt deviation value to be computed correctly.
NOTE
Shunt polarity is in terms of the electrical units of mV/V. If the sensor scaling slope is negative, the shunt polarity in physical units is in the opposite direction. For example, the Up Scale option results in a negative swing in the physical units output data.
Select the channel or channels to be scaled and click Shunt Scaling.
NOTE
Shunt scaling is restricted to inputs without sense lines. These channels are highlighted in green to indicate that the channel is to be experimentally measured.
Before scaling, the system sets the scaling parameters to their shunt defaults. Note that the Physical units and Physical span values can be modified before or after the Electrical zero and Electrical span are measured.
NOTE
To optimize the scaling accuracy, the CX23-R 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 and the channel typically requires zeroing.
Perform shunt scaling in three steps. Click Zero to record the unshunted values, which are used to set the zero offset. Click Install to install shunts as defined by the Shunt polarity parameter. Wait for the installed shunt readings to stabilize and 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.