61
Signametrics
int DMMArmAnalogTrigger
(
int
nDmm, int iPostSamples, double *dThresh
)
emarks
This function is usable for VDC, VAC, Ohms, IAC IDC and Leakage. It sets up the
DMM for analog level trigger operation. In response to this command the DMM
continuously makes measurements, storing them to a circular buffer. A trigger event
occurs when a measured value crosses the threshold, dThresh, in the transition direction
specified by the currently set Edge. The Edge polarity is set using the
DMMSetTrigPolarity function. At the trigger point the DMM makes additional
iPostSamples measurements and stores them to the circular buffer. Following completion
of the capture process, use the DMMGetTriggerInfo function to get information related
to the operation, such as the total number of pre trigger measurements.
The
dThresh
value is in base units, and must be within the selected measurement range.
For example, in the 240 mV range,
dThresh
must be within -0.24 and +0.24. In the
24k
Ω
, range it must be set between 0.0 and 24000.0.
Prior to executing this operation set the measurement function, range, Aperture, Read
Interval and Edge polarity. Between the time this function is issued and the time the
buffer is read, no other command should be sent to the DMM. Two exceptions are the
DMMReady
and
DMMDisArmTrigger
commands.
Read Interval must be set between 0 (default) and 65ms. Aperture must be set between
160ms and 2.5us. The value of
iPostSamples
must be set between 1 and the buffer size.
The buffer size is 80 for Apertures of 160ms to 1.4ms, and 120 for Apertures in the range
of 2.5µs to 625us. The highest Aperture allowed for this operation is 160ms. Aperture
and Read Interval are set using the
DMMSetAperture
and
DMMSetReadInteval
functions, respectively.
e the
DMMReady
to monitor completion of this operation. When ready, read up-to
the above buffer size, using
DMMReadBuffer
or
DMMReadBufferStr
functions. Once
DMMReady returns TRUE, it should not be used again prior to reading the buffer, since
it initializes the buffer for reading when it detects a ready condition.
Parameter
Description
Arm DMM for analog level trigger operation.
#include "SM206032.h"
R
Us
Type/Description
nDmm
int
Identifies the DMM. DMMs are numbered starting with zero.
iPostSamples
int
The number of samples the DMM takes following a trigger pulse.
This number must be between 1 to 80 or 1 to 120. See above details.
dThresh
double
Analog level trigger threshold value
Return Value
The return value is one of the following constants.
Value
Meaning
DMM_OKAY
Operation successfully terminated
Negative value
Error code.
Example
double
Buffer[80];
