Tektronix TEKFAX ADA400A, Инструкция по эксплуатации

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Maintenance
ADA400A Differential Preamplifier
57
Any signals on the inputs of the ADA400A Differential Preamplifier must pass
through the input protection and coupling circuits.
Input Protection. The input protection circuit shunts excessively high-voltage
signals to ground and blows the protective fuse if the current exceeds 1/16 am-
pere for any length of time.
Input Coupling.
The coupling switch for a particular input selects one of the
following connections to the input of the preamplifier: AC, GND (ground), or
DC. For more information on these switch positions, see page 15.
Internal jumpers connect an input impedance of 1 M
Ω
in parallel with 55 pF.
With the jumpers disconnected the input impedance is virtually infinite (10
12
Ω)
.
For more information about these jumpers, see page 12.
The gain switch sets the gain of the preamplifier by selecting the amount of
attenuation at two different points in the circuitry: 1/1 or 1/100 attenuation in the
high-impedance attenuator and 1/1 or 1/10 attenuation in the low-impedance
attenuator. The lowest gain setting, for example, selects the highest total amount
of attenuation.
The offset controls adjust the DC component of the input signal. To keep the
signal from distorting, the signal must be within the dynamic range of the
amplifier. For more information on the dynamic range characteristic, refer to the
notes on page 16.
The Upper Bandwidth Control selects different RC networks in the low-pass
filter. The bandwidth settings are 100 Hz, 3 kHz, 100 kHz, and 1 MHz.
Should the input signal exceed the dynamic range of the output amplifier, the
overrange detection circuit activates the indicator on the front panel.
The gain switch also selects a resistance that appears on the data pin. If the host
oscilloscope is properly equipped (see
Installation on page 2), this resistance
determines the vertical scale factor on the oscilloscope display.
The TEKPROBE interface provides power, signal, and data connections between
the ADA400A Differential Preamplifier and the oscilloscope.
Input Protection and
Coupling
Input Impedance
Attenuation and
Amplification
DC Offset
Low-Pass Filter
Overrange Detect
Scale-Factor Coding
TEKPROBE

Interface