Campbell CDM-A100 Series, Instruction Manual

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CDM-A100 Series
27
8.2.1.1 Sub-Scans
To measure at rates faster than the maximum scan rate of the datalogger, the
SubScan()/NextSubScan instruction pair is added within the datalogger scan.
Using this method, the measurement speed is dictated by the SubInterval and
Units parameters.
The following program makes 20 CDM_VoltSE() measurements on SE 1 at
200 Hz. Note that the notch frequency chosen must accommodate the SubScan
rate. In this example, f
N1
must be 500 or greater to allow for a single-ended
measurement in a 5 ms SubScan. Refer to TABLE 6-2 , Analog Voltage
Measurement Speed
(p. 13)
, for analog voltage measurement speeds associated
with f
N1
options.
CRBasic Example 8-1. Measuring VoltSE() in a Sub-Scan
'Program Example: Measuring VoltSE() in a Sub-Scan
Public FastSE(20)
Dim i 'index counter
DataTable
(FastSETable,True,-1)
Sample (20,FastSE(),FP2)
EndTable
BeginProg
Scan
(1,sec,10,0)
i=1 'initialize index counter
SubScan (5,msec,20) 'repeat the 200 Hz measurement 20 times
CDM_VoltSe (CDM_A108,1,FastSE(i),1,mV5000,1,False,150,500,1,0)
i = i + 1 'increment index counter after each measurement
NextSubScan
CallTable
FastSETable
NextScan
EndProg
8.2.1.2 Burst Measurements
To measure at rates greater than the maximum sub-scan rate of the datalogger,
switch the measurement into burst mode by negating the measurement channel
parameter. In burst mode, the measurement dwells on a single channel and
measures it at rates up to 30 kHz, as demonstrated in the CRBasic example
below. Burst measurements do not allow offset measurement, input reversal, or
excitation reversal.
The measurement rate is determined by the notch frequency (f
N1
). With f
N1
set
to 15000, the measurement is made at 15 kHz. User-entered notch frequencies
will be rounded to the nearest notch-frequency option (see TABLE
6-2 , Analog
Voltage Measurement Speed
(p. 13)
or the CRBasic Help for a full list of
frequency options). The destination parameter must be an array sized to the
total number of measurements to be made. Refer to the
CR6 Measurement and
Control System manual and CRBasic Help for more information. The
following program makes 1,735 CDM_VoltSE() measurements on SE 1 at a
rate of 15 kHz.