Grad Hysteresis Test

1 Diagnostic Link

Diagnostics >> System Function >> Gradient >> Gradient Diagnostics

Diagnostics >> Hardware Location >> System Cabinet >> Gradient >> Gradient Diagnostics

Figure 1. Gradient Diagnostics screen

2 Purpose

The Gradient Hysteresis Test will measure the magnitude of hysteresis produced by the current sensor located in the Gradient Amplifiers. Hysteresis can lead to the perception of unstable gradient DC offsets and may affect the performance of the Supercon Shim tool.

Hysteresis is caused by the magnetic nature of the Gradient Amplifier current sensor. A very large primary current passed through the sensor may cause a permanent magnetization of the sensor's core, such that the secondary current of the sensor will not completely return to zero following the large primary current.

3 Components Tested

  • GP3

  • Gradient Coil

  • Gradient power supply (XFD-PS)

  • Gradient amplifiers (XFA)

4 Requirements

None

5 Block Diagram

None

6 Test Sequence

This test generates large currents, both positive and negative, and measures the resulting secondary current following the pulses. The difference of the two measurements represents the worst-case hysteresis window and thus the total amount of variation that might appear as unstable gradient DC offsets.

7 Expected Results

Output values are judged pass or fail. In the event of failure, the details of the failure can be found in the GE System Log.

In the case of errors click the 1st Error number to see the nature of the error.

8 Etcetera

Click Calculate Time to get an estimate of the time it will take to run the selected diagnostics.

note:

Other than Test Iterations, the Test Options settings should not be changed from their default settings unless instructed to do so by a GE Healthcare engineer. There are very few circumstances when these settings ever need to be changed.

9 Links

None