Operator`s manual

145 Signametrics
Remarks Setup for external hardware trigger operation. Following reception of this
command the DMM enters a wait state. In response to the detection of the
selected iEdge polarity on its external trigger, the DMM makes iSettle + 1
readings and sends the last reading to the PC. It does it at the currently set
measurement function, range, Aperture and Read Interval. This process is
repeated for iSamples times. Therefore, iSamples Trigger pulses must be issued
to complete this process. This function is particularly useful in conjunction with
triggering instruments such as the SM4042 relay scanner. No auto ranging is
allowed in this mode.
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.
The DMM has a small FIFO to reduce the likelihood of an
overrun. This function is usable for VDC, VAC, Ohms, IAC, IDC and RTD
measurements. Use the DMMReadMeasurement to monitor for data
availability, and to read this data.
Parameter
Type/Description
nDmm
int Identifies the DMM. DMMs are numbered starting with zero.
iSettle
int The number of setteling measurements, prior to read value. Must
be set between 0 and 250.
iSamples
int The number of samples the DMM takes following the same
number of trigger pulses. This number must be between 1 and 30,000.
iEdge
Int The edge polarity of the trigger signal. 1 for Positive, or leading
edge, and 0 for negative or trailing edge trigger.
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[100];
DMMSetTrigRead(0,4,100,0);// neg. edge, 4setteling readings
// and 100 samples/triggers
for(i=0;i<100;i++) // read measurement buffer
while( ! DMMReadMeasurement(0, Reading[i]);