Signametrics Corporation SMU2060, Руководство оператора

Страница: 71 / 182

71
Signametrics
for(i=0; i < 50 ; i++) // read 50 readings from buff.
j = DMMReadBuffer(0, &Buffer[i]);
DMMBurstRead
SMU2060

M2064

Description
Setup the DMM for multiple readings operation, sending back measurements as they
come.
#include "SMU2060.h"
#include "USBDMMUser.h"
int
DMMBurstRead(int
nDmm
, int
iSettle
, int
iSamples
)
Remarks
On execution of this command the DMM enters a tight loop, where it takes multiple
measurements, sending them back as they come. This function is similar to the
DMMSetTrigRead function, with the exception that it does not wait for a hardware
trigger to start the process. For each reading returned the DMM takes
iSettle
+ 1 samples,
sending the last sample back. All samples are taken at the set Measurement function,
Aperture and Read Interval currently set. This process repeats for
iSamples
. Following
the issue of this command and until
iSampels
measurements are read back, it is
necessary to keep up with the DMM and read all
iSample
measurements as fast as they
come. Failing to do so will result in communication overrun. Use the
DMMReadMeasurement command to read these measurements. The DMM
communication channel has a limited size FIFO which helps a bit. No auto ranging is
allowed in this mode. The advantage of this function is that it makes measurements with
a consistent sampling rate. Use it carefully and only in cases where this feature is
necessary. It is usable for VDC, Ohms and IDC measurements. Measurement Aperture
should be set to 160ms or lower. The total time it takes to complete this process is equal
to (
iSamples
* (
iSettle
+ 1) * Aperture or * Read Interval if it is not set to 0.
Use the DMMReadMeasurement to monitor when reading becomes available, and to
read the data. Read as many samples as
iSamples
to guarantee proper conclusion of this
capture process.
Parameter Type/Description
nDmm
int Identifies the DMM. DMMs are numbered starting with zero.
iSettle
int The number of settling measurements, prior to read value. Must
be set between 0 and 250. Recommended value is 4.
iSamples
int The number of samples the DMM takes following the same
number of trigger pulses. This number must be between 1 and 60,000,
inclusive.
Return Value
The return value is one of the following constants.
Value Meaning
DMM_OKAY
Operation successfully terminated
Negative Value Error code.
Example
double Reading[250];
DMMBurstRead(0, 2, 250); // take 2 measurements prior to each
// sample. Take a total of 250 samples
for(i=0; i < 250 ; i++) // read them as as they come
while( ! DMMReadMeasurement(0 , Reading[i]) );