Agilent Technologies 8935 Series Especificações descarregar pdf (Página 169)

168 Chapter 7

Periodic Adjustments

Periodic Calibration Menu Descriptions

External Modulation Path Gain

The Audio Frequency Generator Gain program should be performed

before running the External Modulation Path Gain program.

The “path” in this program runs from the external MODULATION IN

connector through the Modulation Distribution assembly, through the

Monitor Select Switch, and then through Audio Analyzer 1 to the Test

Set’s internal DVM. The dc source is Audio Frequency Generator 1

through the AUDIO IN connector and an external cable.

The goal of this procedure is to set the External Level Amplifier gain

DAC (on the Modulation Distribution assembly) to produce a gain of

exactly 4 between the MODULATION IN connector and output of the

Monitor Select Switch. This requires measuring the input and output

levels, calculating the gain, changing the DAC setting, and then

repeating the process until the calculated gain equals 4.

Audio Analyzer 1 Offset

Two DC offsets are measured and downloaded as calibration factors to

the Audio Analyzer 1 assembly. These measurements are determined

under the following conditions:

• Input-select switch grounded

• AUDIO INPUT selected with return conductor grounded

Variable Frequency Notch Filter

The calibration factors for tuning the variable-frequency notch filter are

determined as follows:

The input to the filter is set to 10 evenly-spaced frequencies between

300 and 10,000 Hz. The DAC that tunes the notch filter is adjusted for

best null of the tune error voltage. From this data, three coefficients of a

parabola which best fit the tuning data are calculated using a

least-squares curve fit. The coefficients are then automatically

downloaded into the Test Set’s non-volatile memory.

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Agilent Technologies 8935 Series Especificações Página 169