Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 233)

Section 7. Installation
233
Table 32. TABLE. Summary of Analog Voltage Measurement Rates
Maximum
Rate
100 Hz 600 Hz 2000 Hz
Number of
Simultaneous
Channels
Multiple channels Fewer channels One channel
Maximum
Duty Cycle
100% < 100% < 100%
Maximum
Measaurements
Per Burst
N/A Variable 65535
Description
Near simultaneous
measurements on multiple
channels
Up to 8 sequential differential
or 16 single-ended channels.
Buffers are continuously
"recycled", so no skipped scans.
Near simultaneous
measurements on fewer
channels
Buffers maybe consumed and
only freed after a skipped scan.
Allocating more buffers usually
means more time will elapse
between skipped scans.
A single CRBasic measurement
instruction bursts on one channel.
Multiple channels are measured
using multiple instructions, but
the burst on one channel
completes before the burst on the
next channel begins.
Analog Channel
Sequence
Differential: 1, 2, 3, 4, 5, 6, 7, 8,
then repeat.
Single-ended: 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15, 16,
then repeat.
Differential and single-ended:
1, 2, 1, 2, and so forth.
1, 1, 1… to completion, then
2, 2, 2… to completion, then
3, 3, 3…, and so forth.
Excitation
for Bridge
Measurements
Provided in instruction. Provided in instruction.
Provided in instruction.
Measurements per excitation must
equal Repetitions
CRBasic
Programming
Highlights
Suggest using Scan() /
NextScan with ten (10) ms scan
interval. Program for the use of
up to 10 buffers.
See CRBasic example
Measuring VoltSE() at 100 Hz
Use Scan() / NextScan with a
20 ms or greater scan interval.
Program for the use of up to
100 buffers. Also use
SubScan() / NextSubScan with
1600 µs sub-scan and 12
counts.
See CRBasic example
Measuring VoltSE() at 200 Hz
Use Scan() / NextScan with one
(1) second scan interval. Analog
input
Channel number is
preceded by a dash ( - ).
See CRBasic example Measuring
VoltSE() at 2000 Hz
7.8.12.1 Measurements from 1 Hz to 100 Hz
Assuming a minimal CRBasic program, measurement rates between 1 and 100 Hz
are determined by the
Interval and Units parameters in the Scan() / NextScan
instruction pair. The following program executes VoltSE() at 1 Hz with a 100%
duty cycle.
Table 33. Measuring VoltSE() at 1 Hz
PipeLineMode '<<<
Public FastSE
DataTable (FastSETable,1,-1)
Sample (1,FastSE(),FP2)
EndTable