Excitation on/off:
Provision for separately switching off the bridge voltage
while the remainder of the measuring circuit remains operational. This is an
important and useful feature, particularly when measuring dynamic strains. Any
output observed when the bridge voltage is switched off must be due to
electrical noise, as the output cannot possibly be the result of resistance
changes in the measuring circuit when a bridge voltage is not present. The
ability to turn off the bridge power is therefore a useful diagnostic tool for
establishing whether electrical noise is a problem.
Voltage and current excitation:
For the balanced bridge, it does not matter
whether the power supply is of the constant
-
voltage or constant
-
current variety.
In both cases, the output is zero for the resistively balanced state. However,
resistive balance circuits may be used with constant current excitation to obtain
an initial zero balance of the instrument output when the bridge itself is
unbalanced.
Sense lines:
Remote sense or, more correctly, remote sensing of excitation
voltage, is commonly recommended for use with precision, commercial
transducers to prevent leadwire resistance changes (due to changes in either
temperature or length) from affecting transducer span, or sensitivity.
Leadwire attenuation presents a potentially significant error source in
transducers utilizing a Wheatstone bridge circuit. The leadwires represent a
parasitic resistance, and a portion of the excitation voltage intended for the
bridge circuit is dropped in the leadwire system, reducing the voltage actually
present at the transducer, and effectively reducing the transducer sensitivity.
In Perception
To select the required settings in the Perception software, do the following:
1
In Perception, go to the
Settings
sheet.
2
In the task pane, select the
Bridge
in the
Input
section.
3
Select one or more channels.
GEN3i
264
I3763-3.1 en HBM: public
