Operator`s manual

45 Signametrics

filled, there will be some NULL readings in the buffer, followed by pre-trigger and post-trigger is

readings. Following capture use the DMMGetTriggerInfo() function to retrieve information such as the

number of NULL readings, Pre-Trigger samples and buffer fill cycles.

4.13.1.2 Delayed Triggered Operation

In this trigger mode of operation, following the reception of the selected trigger edge, the DMM waits for

the specified delay, and then it takes from 1 to 120 (or 1 to 80 if high resolution) measurements. The

delay can be set from 10us to 1s.

The specified number of measurements is stored in the buffer. At the end of this operation, the internal

buffer pointer points to the beginning of the buffer, such that reading the buffer starts with the first sample

taken. To read all samples resulting from this operation, use one of the buffer read functions. See

DMMDelayedTrigger() function for details.

4.13.2 Analog Threshold Trigger

This mode of operation is entered by issuing the DMMArmAnalogTrigger command. In this mode, while waiting

for a trigger event, the DMM makes repeated measurements and places them in the internal buffer, as to provide

pre-trigger samples. All measurements are made using the currently set range, function, Aperture and Read Interval.

Trigger event occurs when the input value transverses through the set Threshold (dThresh) value, in the currently

set directions dictated by Edge (see DMMSetTrigPolarity). Following the trigger point, if enabled, the Sync output

is activated (see DMMSetSync), and iPostSamples measurements are taken. At the end of this process the Sync

output is deactivated. This mode may be aborted by issuing the Disarm command (DMMDisArmTrigger). Use

DMMArmAnalogTrigger(int nDmm, int iPostSamples, double *dThresh). In addition to triggering on a value,

this function may be used as a zero-crossing detector, where the Sync may be used as a flag.

he dThresh value is in base units, and must be within the selected measurement range. For example, while in the

se 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

r reading when it detects a ready condition.

240 mV range, dThresh must be within -0.24 and +0.24. In the 24kΩ, range it must be set between 0.0 and

24000.0.

again prior to reading the buffer, since it initializes the buffer fo

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

Figure 4-13. Analog Threshold Trigger operation with Positive Edge and Sync enabled.

ings. These include DMMSetBuffTrigRead, DMMSetTrigRead,

MMTrigger, DMMBurstRead and DMMBurstBuffRead. Read about these functions in the Windows

Command Language section (5.6) for details.

4.13.3 Software Generated Triggered Operations

There are several software trigger functions. They can commend the DMM to make a predefined number of

readings, with a specified number of settling read