1250 Frequency Response Analyzer Options
AMK/1250/2 15-11
15.1.9 MEASURING HARMONICS: USE OF ORDER ANALYSIS
Section 1.5 above details the use of Ratio mode to measure at a harmonic of the input
trigger frequency. The disadvantages of this mode, arising from its inability to phase
lock to the trigger source, can be overcome by using Order Analysis instead of
Harmonic Analysis:
1. Follow the procedure given in Section 1.7 above for establishing the Sync. Locked
state, leaving RATIO set to 0 (i.e. 'off', its default state).
2. Set the HARMONIC soft key in the [ANALYZER COMMON] menu to 1 (its default
state), and the ORDER soft key to the required harmonic (2 to 16).
The measurements obtained using Order Analysis benefit from the following
advantages, compared to the Ratio mode/Harmonic Analysis method:
a) Results are far more accurate because the 1250-works in phase locked mode.
Hence, even long integration times may be selected to give accurate results.
b) Phase information is meaningful because each measurement is made in phase
locked mode.
c) The full range of results can be obtained very much more rapidly, because in Order
Analysis all sixteen harmonics are computed from a single measurement (see
Chapter 5, Section 2.4 "Order").
Order Analysis cannot be used, however, at the same time as Autointegration, or when
the trigger frequency exceeds 400Hz.
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