HBM Genesis GEN5i User Manual page 280

280
Excitation on/off: Provision for separately switching off the bridge voltage
while the remainder of the measuring circuit remains operational 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 doesn't matter if
the power supply is of the constant-voltage or constant-current variety. In both
cases the output will be 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 make 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.
GEN5i
I2679-4.0 en