Overview of application
The creation of user-defined waveforms is useful for simulating ac line disturbances that are unique to the operational environment of the device being tested, and then measuring that device’s suscepti- bility to the disturbance. This is the fundamental objective of environmental test standards that per- tain to the ac line. A specific example is the draft for IEC 77A (Secretariat) 101 draft (dated 10/15/93), which defines the test and measurement methods for evaluating electronic and electrical equipment immunity to voltage harmonics and inter-harmon- ics on the ac line. Upon subjecting the equipment to the voltage harmonics, it must recover to its full operative capabilities to meet the “pass” criteria of this draft.
For this example, a waveform with harmonic volt- age content as defined by the IEC 77A (Secretariat) 101 draft (dated 10/15/93) will be created, stored, and generated by the ac power source/analyzer.
| Harmonic Voltage Levels (for 120 Vrms) |
| | |
Harmonic Number | Class 1 | Class 2 |
| | |
3 | 9.6 V | 7.2 V |
| | |
5 | 10.8 V | 9.6 V |
| | |
7 | 6 V | 8.4 V |
| | |
11 | 2.4 V | 8.4 V |
| | |
13 | 2.4 V | 7.2 V |
| | |
The equipment under test used for this example has an ac input rating of 120 Vrms, 60 Hz, and
5 Arms. The waveform generated will comply with the Class 1 harmonic combination (as currently proposed) shown above. This draft specifies that the equipment under test must be subjected to the harmonic waveform of either Class for 2 min- utes, succeeded by 2 minutes of the fundamental (120 Vrms sinewave) waveform.
Agilent 6800 series features used
•Non-volatile, user-defined (arbitrary) waveform creation/storage
•rms voltage programming
•Frequency programming
•Waveform shape transient generation
•List transient mode
Advantages/benefits of the Agilent 6800 series solution
The user-defined waveform is stored in non- volatile memory, eliminating the need for con- stant re-creation and making it easy to recall the waveform as the test is needed. A List of out- put waveforms can be generated by combining built-in and user-defined waveforms, simplifying complex test sequences. The user-defined wave- form can be recalled as if it was one of the stan- dard output shapes (such as sine and square waveforms) and can be used in all modes where the FUNCtion:SHAPe command is valid.
Implementation details
How the 6800 series implements user-defined waveforms
The computer is used to generate an array of
1024 voltage amplitude points that represent one cycle of the 77A (Secretariat) 101 Class 1 wave- form. This data is sent to the ac source as a named (CLASS 1) user-defined waveform and is stored in a non-volatile memory location. The List mode of the ac power source/analyzer is used to sequence through the appropriate output settings at 2-minute intervals as per the draft. The programmed param- eters for each List point are shape (waveform) and dwell time. The rms voltage and frequency output settings remain in Fixed mode. The first List point is the fundamental waveform (120 Vrms sinewave at 60 Hz) and will be output upon receipt of a tran- sient trigger for 2 minutes. The CLASS 1 waveform will be output for 2 minutes as part of the second List point. After this 2-minute test, the fundamen- tal waveform will be output again as part of the final List point.
