Microsoft LPF-00004 Manual del operador descargar pdf (Pagina 143)

ADJUSTMENT PROCEDURES Page 125

YBER

380, COPYRIGHT MARCH 2002, AXON INSTRUMENTS, INC.

ADJUSTMENT PROCEDURES

There are very few adjustments that can be made inside the CyberAmp. The gain accuracy is

determined by fixed, precision resistors, while the internal offsets are automatically corrected each

time the unit is switched on and each time relevant settings, such as the gain, are changed.

Tuning of the notch filter is the only adjustment that may be necessary to perform on a correctly

functioning CyberAmp 380. The notch filter must be tuned to the local line frequency, either 50 Hz

or 60 Hz. CyberAmps are normally shipped from the factory with notch filters set to 60 Hz, but both

50 Hz and 60 Hz are tested.

If necessary, notch filters are simply tuned with an oscilloscope (or data acquisition system) and a

small screwdriver.

Tuning the Notch Filter

Connect an oscilloscope to the channel #1 output. Set the oscilloscope gain to 100 mV/div. Set the

time base to 10 ms/div. Set the trigger circuit to LINE.

Remove the top cover of the CyberAmp. Locate the trim potentiometers for adjusting the notch

filters, labeled RP102 to RP802 for channels 1 to 8 respectively. These are about 3/4 of the way

towards the back of the instrument.

Switch to the directory where you have loaded the CMD300 software and type the following

command:

CMD300 TEST NOTCH

This command energizes a test oscillator at the same frequency as the power line (either U50 or

60 Hz, depending on the country) connected to the positive input of all channels. Simultaneously, the

gain of each channel is set to unity. At the end of the test, all CyberAmp settings are restored to their

values prior to the test.

If the notch has not been tuned, the amplitude of the test waveform could be up to 600 mV

p-p

(upper

trace in Figure 39). The test waveform is not a simple sine wave -- it contains many harmonics at the

line frequency.

Adjust trim potentiometer RP102 to minimize the signal amplitude. This will be about 50 mV

p-p

when

properly tuned (lower trace in Figure 39). When the notch filter is tuned, the waveform no longer

looks sinusoidal because the higher-frequency harmonics remain.

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Microsoft LPF-00004 Manual del operador Pagina 143