HP WaterSkis E1412A, WaterSkis E1312A Interrupt Priority, Setting the Line Frequency Reference

Interrupt Priority

The HP E1312A and HP E1412A Multimeters are VXIbus interrupters. However, there is no interrupt priority level setting to be made on the module. Interrupt priority level, setup, and activation are configured on the resource manager which is the interface to the VXIbus and contains any instrument drivers required to communicate with a VXI module. Your resource manager could be a VXI command module, embedded PC controller, the PC-based VXLink Interface (ISA-to-VXI), the Series 700 workstation VXI-MXIbus interface or another VXI controller. To configure the interrupt priority on the HP E1405B and HP E1406A Command Modules, you would use the DIAGnostic:INTerrupt command subsystem. Refer to your resource manager’s documentation for information on setting the system’s interrupt priority.

Setting the Line Frequency Reference

Checking the Line

Frequency

Reference

You must set the line frequency reference to the line frequency of the power source to your mainframe for maximum normal mode rejection (NMR). NMR is the multimeter’s ability to reject power line frequency noise in a DC voltage or ohms measurement. You should set the multimeter’s line frequency reference to the exact power line frequency (50, 60 or 400Hz). Failure to set the line frequency reference to that of your source will cause reading errors.

You use the CALibration:LFRequency command to set the line frequency reference. The default setting at power-on is 60Hz. If you use 50Hz or 400Hz you need to set the line frequency reference for maximum NMR. Specifying 400Hz actually sets the line frequency reference to 50Hz since 50Hz is a sub harmonic of 400Hz. Executing a CALibration:LFRequency? will return +50 after executing CAL:LFR 400 to set the line frequency reference to 400Hz.

The line frequency reference setting is also useful when the device being measured operates at a different frequency than the multimeter. For example, if the multimeter has a power line frequency reference of 60Hz and the device being measured has a power line frequency of 50Hz, maximum NMR is achieved by setting the multimeter’s reference frequency to 50Hz by executing:

CAL:LFR 50

The CALibration:LFRequency? command returns the present setting of the power line frequency reference. The command returns +50 or +60. For a setting of 400Hz, +50 is returned since 50Hz is a sub harmonic of 400Hz.

Chapter 1 HP E1312A and HP E1412A Multimeter Module Setup 17