Agilent Technologies HP 8719D Service Manual page 285

Analog Bus
Description of the Analog Bus
The analog bus is a single multiplexed line that networks 23 nodes within the
instrument. It can be controlled from the front panel, or through HP-IB, to
make voltage and frequency measurements just like a voltmeter, oscilloscope, or
frequency counter. The next few paragraphs provide general information about
the structure and operation of the analog bus. See "Analog Bus Nodes, n below,
for a description of each individual node. Refer to the "Overall Block Diagram,"
in the "Start Troubleshooting" chapter, to see where the nodes are located in
the instrument.
1 O-26
Turning this ON switches out both the A and B
attenuation circuits; they cannot be switched
independently. Be aware that input signal levels
above -30 dBm at the sampler input will saturate
the ADC and cause measurement errors.
switches in both of the A10 IF attenuators for
checking the Al0 IF gain amplifier circuits. Small
input signals will appear noisy, and raise the
apparent noise floor of the instrument.
allows you to store the correction constants that
reside in non-volatile memory (EEPROM) onto a
disk. Correction constants improve instrument
performance by compensating for specific operating
variations due to hardware limitations (refer to the
"Adjustments" chapter). Having this information on
disk is useful as a backup, in case the constants are
lost (due to a CPU board failure). Without a disk
backup the correction constants can be regenerated
manually, although the procedures are more time
consuming.
enables and disables the analog bus, described
below. Use it with the analog in menu, (a
description of this menu follows).
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