Instrument trigger model Acquiring measurements on the DMM is done as the result of triggering. This section describes how to configure triggering.
Pressing opens the following menu:
The menus above allow you to configure measurement triggering, and you can also use the VMC Out softkey to set the edge slope of the VM Comp (voltmeter complete) output on the instrument's rear panel. This connector issues a signal whenever the voltmeter finishes taking a measurement to allow you to signal other devices in a measurement system. For accurate displayed statistics of AC measurements in Front Panel mode, the default manual trigger delay ( > Delay Man) must be used. The (Trg Src) menu allows you to select one of these trigger sources:
Auto - the instrument continuously takes measurements, automatically issuing a new trigger as soon as a measurement is completed.
Single - the instrument issues one trigger each time the front panel key is pressed.
Ext - the instrument issues one trigger each time an edge of the appropriate slope arrives at the rear-panel Ext Trig connector. You can specify the slope on the softkey menu that appears when Trg Src is set to Ext.
In the Single, and Ext modes, you can specify the number of samples to be taken per trigger by using the Samples/Trigger softkey. The Single and Ext modes can both buffer up to one trigger, meaning that if you press or receive an external trigger while a series of measurements is in progress, the instrument will finish that series of measurements and then immediately launch a new series of measurements based on the trigger.
If multiple or external triggers are issued during a series of measurements, all triggers received after the first are discarded.
The menu also configures the delay that occurs before each measurement is taken, regardless of the trigger mode (Auto, Single, or Ext). This may be either automatic (the delay is based on the DMM’s settling time) or manual (you specify the delay time).
Finally, note the and keys on the front panel. In Auto trigger mode, pressing stops and resumes measurements, and pressing switches the instrument to single trigger mode. In the Single and Ext modes, pressing stops readings if they are in progress, or switches the mode to Auto if readings are stopped.
Trigger delay and multiple samples The instrument inserts a trigger delay between the occurrence of a trigger and the first measurement. When Auto is used (Delay Auto softkey), the instrument automatically determines the delay based on function, range and integration time. However, you may need to manually set a delay (Delay Man softkey) longer than the automatic delay to allow the input to settle before pacing a burst of measurements, for measurements with long cables, or for measurements of high capacitance or high impedance signals.
If you have configured the instrument for more than one sample per trigger (Samples /Trigger softkey), in all cases, the first sample is taken one trigger delay time after the trigger occurs.
Storing and clearing readings You can store up to 1,000 measurements in the reading memory. Readings are stored in a first-in, first-out (FIFO) buffer; when reading memory is full, the oldest readings are lost as newer readings are taken.
In Local (front panel) mode, the instrument collects readings, statistics, trend chart and histogram information in the background, so if you select any of those options, the data is ready for viewing. In Remote (SCPI) mode, the instrument does not collect this information by default.
Changing the instrument from Local to Remote does NOT clear any readings in memory. Changing the instrument from Remote to Local DOEs clear any readings in memory.
In general, you turn the reading of measurements on and off by pressing , as described above.
You can also take one reading or a specified number of readings by pressing . To save readings, press > Save Readings. Then use the menu that appears to configure the location where you want to save the readings:
When finished configuring reading storage, press Done > Save Readings to save the readings in memory to a file.
Clearing Reading Memory The following actions clear reading memory: l Changing the measurement function l Pressing any Clear Readings softkey l Transitioning in or out of Probe Hold l Changing temperature units l Changing any dB/dBm parameters l Changing any histogram binning parameter l Changing the temperature probe or R0 l Recalling a stored state l Calibrating the instrument l Switching between 3 A and 10 A inputs l Changing the position of the Front/Rear switch l Transferring from Remote to Local mode l Turning Null on or off or changing the Null value
These actions do not clear reading memory: l Changing measurement parameters, such as range and aperture. l Turning limits on or off, or adjusting limit values l Pressing in front panel auto trigger mode l Changing the trend chart Recent/All softkey l Changing samples per trigger or trigger delay l Changing display modes l Changing the VM Comp output polarity l Changing the digit mask l Changing the histogram, bar meter, or trend chart scale l Changing user preferences l Executing self-test
Probe Hold Because probing small areas requires careful concentration, it is often difficult to read the instrument display while taking measurements. Therefore, the instrument includes a front panel key that allows you to take readings without viewing the display. You can generate up to eight readings and hold them on the display for later viewing. These readings may be of different measurement types and you may clear displayed readings at any time.