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EX1629 Command Set
203
vtex1629_measure_excitation_voltage
F
UNCTION
P
ROTOTYPE
ViStatus vtex1629_measure_excitation_voltage (ViSession
vi
, ViInt32 _VI_FAR
channels[]
, ViInt32
numberOfChannels
, ViInt32
excitationSource
, ViInt32
sampleCount
, ViReal64 _VI_FAR
measuredValues[]
,ViPInt32
numMeasuredValues
, ViBoolean
euConversion
);
F
UNCTION
P
ARAMETERS
vi
= contains a session handle to the instrument. This handle is obtained by the function and remains valid until the
session is closed.
channels
= an input integer array containing a list of channel numbers for which the excitation will be measured.
Valid input values: 0 to 47.
numberOfChannels
= the size of the
channels
list. Valid input values: 1 to 48.
excitationSource
= an integer input value indicating the excitation sense lines to be measured. Valid input values: 0
or 1.
sampleCount
= an integer input value indicating the number of measurements to average. See the
Description
section below for valid input values.
measuredValues
= a real return array of the measured values. The measured values are placed in the array
according to the
channels
array passed to the function. In other words, for every channel number in
channels
, there
will be a corresponding excitation voltage measurement in
measuredValues
.
numMeasuredValues
= an integer return value that indicates the number of measured values returned in the
measuredValues
array.
euConversion
= a Boolean input value indicating whether the measured values should be used for future EU
conversions.
D
ATA
I
TEM
R
ESET
V
ALUE
Not applicable to this function.
D
ESCRIPTION
This function measures the total excitation voltage [(positive excitation voltage) – (negative excitation voltage)] for
a list of channels. Setting the
euConversion
parameter to VI_TRUE (1) indicates that these values are to be used for
future EU conversions. Setting it to VI_FALSE (0) causes this data to be discarded after being read. Using
VI_TRUE is a short cut that eliminates the need for invoking vtex1629_set_euconv_excitation for each channel.
Measuring the excitation voltage improves the accuracy of the strain gage EU Conversions.
The
excitationSource
parameter indicates the source to be used for measuring the excitation voltage. The parameter
values are defined as follows:
VTEX1629_EXCITE_SRC_LOCAL (0)
= local sense
VTEX1629_EXCITE_SRC_REMOTE (1) = remote sense
If the remote sense lines are not connected to the external strain bridge, such as in quarter-bridge configuration,
either setting can be used. The values in either case are the same. However, if the remote sense lines are connected
to the bridge, as they ideally should be in half- or full-bridge configuration, the remote sense lines should be
measured, as they represent the true source output seen by the bridge.
NOTE
This measurement is done with a sampling rate of 500 Hz. This requires that the instrument
configuration be modified during the execution of this function, and, thus, requires a sync (see
vtex1629_soft_synch) event to be generated before any other acquisitions are performed.
The
sampleCount
parameter typically can be set to values between 1 and approximately 3000 samples if sampling
is performed at 500 Hz and filtering turned off. Since the maximum number of samples that can be stored is
dependent on available memory and other settings this value can vary.
