Specifications

resolution drops to around 31 µV per LSB so the stray capacitances discharging
after the 15.5 volt measurement are now only one sixteenth as significant and thus
reduce any required settling delay. Of course for most thermocouple measurements
a gain of 64 can be used with the Range Amplifier set to the 4 volt range. At this
setting the A/D resolution for one LSB drops to about 122 µV and further reduces
or removes any need for additional settling delay. This improvement is
accomplished without any reduction of the overall measurement resolution.
NOTE Filter-amplifier SCPs can provide improvements in low-level signal measurements
that go beyond just settling delay reduction. Amplifying the input signal at the SCP
allows using less gain at the Range Amplifier (higher range) for the same
measurement resolution. Since the Range Amplifier has to track signal level
changes (from the multiplexer) at up to 100 kHz, its bandwidth must be much
higher than the bandwidth of individual filter-amplifier SCP channels. Using higher
SCP gain along with lower Range Amplifier gain can significantly increase
normal-mode noise rejection.
Adding Settling Delay
for Specific Channels
This method adds settling time only to individual problem measurements as
opposed to the SAMPle:TIMer command that introduces extra time for all analog
input channels. If problems are seen on only a few channels, use the
SENS:CHAN:SETTLING <num_samples>,(@<ch_list>) command to add extra
settling time for just these problem channels. What SENS:CHAN:SETTLING does
is instructs the VT1419A to replace single instances of a channel in the Scan List
with multiple repeat instances of that channel if it is specified in (@<ch_list>). The
number of repeats is set by <num_samples>.
Example:
Normal Scan List:
100, 101, 102, 103, 104
Scan List after SENS:CHAN:SETT 3,(@100,103)
100, 100, 100, 101, 102, 103, 103, 103, 104
When the algorithms are run, channels 0 and 3 will be sampled three times and the
final value from each will be sent to the Channel Input Buffer. This provides extra
settling time while channels 1, 2, and 4 are measured in a single sample period and
their values also sent to the Channel Input Buffer.
Programming the VT1419A Multifunction
Plus
Settling Characteristics
Chapter 3 103
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