Omega Engineering OMB-NETSCAN, Руководство пользователя

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Appendix C Configuration Aspects for Programmers
NetScan User’s Manual C-5
High-Speed, Single-Channel Mode
The High-speed, single-channel mode, also known as burst mode, is used for post-acquisition waveform
analysis of AC and DC voltages. In this mode, NetScan can sample from 38.5 Hz to 20.0 kHz, and store the
data in memory. Note that NetScan’s memory can be expanded up to 8 Mbytes.
When performing post-acquisition waveform analysis, such as Fast Fourier transforms, NetScan can return each
data point in a waveform. In addition, NetScan can provide the true RMS value of an AC voltage.
Because high sampling rates can be achieved in the High-speed, single-channel mode, the conditions indicated
in the following table apply.
High-Speed, Single-Channel Mode
Necessary Item Conditions Due to High Sampling Rates
Item Condition
High/Low./Last registers Disabled
Alarms Disabled
Trigger Start Software trigger only (@ command)
Trigger Stop By Count only
Pre-Trigger Disabled
Post Stop Count Disabled
Time Stamping Disabled
Alarm Stamping Disabled
Digital Input Stamping Disabled
Averaging weight 256, forced default (can not be changed)
Frequency In regard to AC voltage, frequency must be such
that it results in a sufficient whole even number of
samples per line cycle.
NetScan collects samples for the selected channel in blocks of 256 samples in one time increment. This appears
similar to a scan of 256 channels while in the normal (multiple-channel) mode since you must …
•
program the number of 256 sample blocks to acquire in the post trigger count parameter of the
Y
command, and will
•
retrieve the data from NetScan as “post trigger count” scans of 256 samples
Note: High-speed, single-channel mode is a “one-shot” operation. It permits NetScan to collect the specified
number of samples, then stops. The mode is not continuous, nor does it allow for memory overflow
and wrap-around. The maximum number of samples is limited by the amount of memory available.
See the
Y
command reference (in Appendix A) for related information.
Note: In regard to AC voltage measurements, NetScan only supports AC voltages having an input signal
frequency which is an integer multiple of the AC line cycle. In order to compute an accurate RMS
value you must program a frequency which will yield a sufficient “whole even number” of samples per
line cycle.
Note: In High-speed, single-channel mode, upon completion of the acquisition, AC voltage RMS values can
be retrieved with the
U17
query command.
To use the High-speed, single-channel mode use the following commands, or use ChartView (see Chapter 4).
Note that these commands (or ChartView equivalent) are all that is needed to initiate the High-speed, single-
channel mode data acquisition.
M#1 ‘Select high-speed, single-channel mode
Cchan#,type ‘Select channel number and voltage-range
F#freq ‘Select sampling frequency where
38.5 <
freq
< 2000.0
Y0,count,0 ‘Select count where count is the number of 256 sampling
blocks to be acquired
T1,8,0,0 ‘Arm the system to start on @, stop on count
@ ‘Start the acquisition