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FET Multiplexer
Excitation Voltage
CAUTION
Strain Gage
Multiplexer
Configurations
Creating a Scanning
Multimeter Instrument
Chapter 1
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The internal bridge excitation voltage for the HP E1357A/E1358A FET
strain gage multiplexers is +4.6V referenced to mainframe chassis, and
current limited at 450 mA. The voltage is accessed as indicated by the
(movable) jumper setting shown in Figure 1-4.
When the FET multiplexers are shipped from the factory, the jumper is in
the "ON" position. If the jumper is moved to the "OFF" position, the
excitation voltage must be externally supplied as explained in Chapter 2.
If the bridge excitation voltage is externally supplied, be sure
that the jumper is not installed, or with the FET multiplexers,
ensure that the "STRAIN EXCITATION" jumper is in the "OFF"
position. Otherwise, unpredictable strain measurements may
result.
In a B-Size or C-Size VXIbus system, the strain gage multiplexers can be
used in two configurations:
•
Scanning Multimeter
(multiplexers are used with an HP E1326B/E1411B Multimeter)
•
Switchbox
(multiplexers are used with an external voltmeter)
Guidelines for creating a scanning multimeter and switchbox follow.
In a scanning multimeter instrument, signals measured by the HP
E1326B/E1411B Multimeter are input via the multiplexer channels.
Channel openings and closings are controlled by the multimeter through
commands sent to the multimeter. To create a scanning multimeter
instrument:
•
The instrument must have one module (the multimeter) assigned as
the instrument identifier. The instrument identifier is the module
with a logical address that is a multiple of 8 (8, 16, 24, ...). The HP
E1326B/E1411B Multimeter has a factory set logical address of 24.
•
The modules in the scanning multimeter instrument must have
successive logical addresses, beginning with the logical address of the
multimeter. For example, with a multimeter logical address of 24, the
logical addresses of the multiplexers must be 25, 26, and so on.
•
The strain gage multiplexers have a factory set logical address of
112. The logical address is changed using the logical address
switches shown in Figure 1-5.
Getting Started with the Strain Gage Multiplexers
19
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