Linear And Logarithmic Scanning; Recording Procedure - BRUEL & KJAER 2010 Instructions And Applications

Heterodyne analyzer

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Note: In equation (1) f is the highest measuring frequency, which may be

different from the limit of the range considered. On the other hand for a

linear sweep, even if the range of frequencies investigated is inside the

selected range the scanning speed limit is always the same.

The choice between a linear and a logarithmic sweep is discussed in the

following section.

6.1.2. Linear and Logarithmic Scanning

The 2010 enables either a linear or a logarithmic frequency sweep to be

made on all three frequency ranges 2Hz- 2 kHz, 20Hz- 20kHz and

200 Hz- 200 kHz. The choice between the two sweeping modes may be

made to suit the particular application. Although logarithmic sweep is the

most widely used, certain applications are well suited to a linear scan.

For example:

1. Detailed investigation of closely spaced pure tones (e.g. harmonics) at

high frequencies.

2. Accurate graphical measurement of

factor of a resonance from the

half power points.

3. Analysis in a narrow frequency band, which allows accurate frequency

determination from recording paper.

6.1.3. Recording Procedure

DC Recording

Recording from the DC output of the 2010 utilizes the wide dynamic

range (60 dB) and the wide range of selectable averaging times of the

RMS

rectifier.

The controls of the Level Recorders are shown in Figs.6.1 and 6.2. The

procedure for recording an analysis is as follows:

1. Connect the instruments as shown in either Fig.6.3 or Fig.6.4. The

scanning facility of the 2010 may be mechanically driven using the

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