Microsoft LPF-00004 Manuel de l'opérateur télécharger pdf (Page 26)

Page 8 FUNCTIONAL DESCRIPTION

CYBERAMP 380, COPYRIGHT MARCH 2002, AXON INSTRUMENTS, INC.

Input connectors.

There are two inputs for each channel: a BNC connector for single-ended

inputs and a 15-pin D connector for single-ended or differential inputs. The inner contact on

the BNC is connected to the positive input of the amplifier. The shell of the BNC is connected

to ground.

In addition to the positive and negative inputs, the D connector also has ±15 V supply pins, a

precision +5 V supply for bridge transducer excitation, and other test and sense pins (see the

Making Your Own Adapter of Active Probe chapter).

10)

Overload.

For each channel, a front-panel LED lights during the time that the input to the low-

pass filter or the output of the post-filter gain stage exceeds ±10 V. The overload is noted by

the internal microprocessor and the host may interrogate the CyberAmp 380 to determine if an

overload has occurred on any of the channels since the last request for this information.

11)

Output filter.

Just before the processed signal is made available as output, it is passed through

a passive low-pass filter consisting of a resistor and a capacitor. (Their values are

approximately 420 Ω and 3,300 pF.) The bandwidth of this filter is quite high, about 120 kHz.

This filter serves two purposes. First, it removes any high-frequency noise introduced by the

post-filter electronics. Second, the resistor increases the output protection.

12)

Output connector.

The output from each channel is available on a BNC connector. The shell

of the BNC is connected to ground.

General Features

Electrode test.

A ±0.5 volt, 10 Hz test waveform can be applied to each input through

individual 1 MΩ resistors. All inputs, positive and negative, are driven simultaneously. For

typical electrode resistances of 10 kΩ or less, this test signal injects a ±0.5 µA current (1 µA

p-p

)

into the electrode. The test current is balanced around zero in order to minimize electrode

polarization.

Power-up offset calibration.

Five minutes after the CyberAmp 380 is switched on, the

internal voltage offsets on all channels are automatically calibrated. All outputs are grounded

for a few milliseconds during this procedure.

Audio monitor.

The audio monitor makes audible the signal on any one channel. The audio

monitor is not under program control. There are two modes of operation. "Click" mode is used

to monitor the AC activity of the selected signal. "Tone" mode is used to monitor the DC and

low-frequency activity of the selected signal. There is a volume control, an offset/squelch

control, a speaker and a headphone jack.

Amplitude calibration waveform.

A continuously generated calibration waveform is

available from a BNC connector on the front panel. This waveform is an accurate monopolar

square wave, 0 to +10 mV, at approximately 1 kHz. It is useful for verifying the operation and

accuracy of the data acquisition system.

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Microsoft LPF-00004 Manuel de l'opérateur Page 26

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