Last Updated: August 29, 2007
This topic provides information about the triggering of measurements. Refer to the following sections:
The triggering process controls the present and future states of the test set during the measurement cycle. Triggers are set up using the SETup commands and can be set up when a measurement is in the inactive state. A measurement is activated (selected) with an INITiate command. If a measurement is initiated while it is already in its measurement cycle, it aborts the current measurement and restarts it. The active state is not a single state but a collection of any state other than the inactive state. To deactivate (de-select) the measurement, you use the INITiate:<measurement mnemonic>:OFF command.
From the front panel, a measurement is activated by selecting it in the Measurement Selection window. A measurement is deactivated by clearing the measurement in the Measurement Selection window.
If the test set has just been turned on, or any form of preset has been performed, then the measurement state is inactive.
If a measurement has been initiated with the INITiate command but has not been triggered, or a measurement has been selected in the Measurement Selection window but has not been triggered, then the measurement state is wait for trigger.
If the trigger arm is set to single, the trigger source is available, and the trigger qualifier (optional) is satisfied, the measurement state transitions to measuring and measurement results are available. The state then transitions to idle (awaiting another INITiate).
If the trigger arm is set to continuous, the trigger source is available, and the trigger qualifier (optional) is satisfied, the measurement state transitions to measuring and measurement results are available. The measurement is continually triggered until the measurement is deactivated. Measurement results are only available after the measurement completes and before it rearms. The measurement is deactivated using the INITiate:<measurement mnemonic>:OFF or clearing the measurement in the Measurement Selection window.
A measurement trigger causes hardware (for example, a sampler) to capture data which is used by a measurement algorithm to produce a measurement result. Not all of the trigger source choices are available in every measurement, or every application.
Any measurement’s trigger source is available remotely from all the applications, even if the measurement isn't applicable to the currently active application. If you set any trigger source settings for an application that is not the currently active application all the settings are maintained when you switch applications.
When external triggering is selected, an external trigger signal must be applied to the BBP TRIG IN connector on the test set's rear panel, in order to trigger data capture. The trigger occurs on the rising edge of the applied signal.
When fall triggering is selected, a measurement dependent threshold is used to define the trigger point on the envelope of the signal being measured. The envelope amplitude must be above this threshold and remain there for a measurement-dependent period of time before the trigger is qualified.
When immediate triggering is selected, the trigger occurs as soon as any pre-trigger samples required by the measurement algorithm are taken. Data capture is triggered when the measurement is initiated.
When RF generator ARB triggering is selected, the measurement is triggered from ARB waveform. To use this method of triggering the RF Generator's Modulation Mode must be set to ARB and a Waveform File selected. This method of triggering is not available in the General Purpose Application as this application does not contain any ARB waveforms.
When rise triggering is selected, a measurement dependent threshold is used to define the trigger point on the envelope of the signal being measured. The envelope amplitude must fall below this threshold and remain there for a measurement-dependent period of time before the trigger is armed. After the trigger is armed, a trigger occurs as the envelope amplitude increases and passes through the threshold.
SCPI command: SETup:<measurement mnemonic>:TRIGger:SOURce[?]
Trigger arm determines if a measurement makes one measurement then returns to idle (single), or automatically rearms on completion of a measurement and repeats the process (continuous).
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When operating the test set remotely, the recommended setting for the trigger arm parameter is single. This ensures proper operation of the INITiate:DONE? query which is used to control the retrieval of measurement results when measurements are initiated concurrently. When a continuously armed measurement gets a result, it is available to any currently pending (waiting, hanging) FETCh? query. Then another measurement cycle is started immediately. At this point the results are no longer valid. The INITiate:DONE? query is used to determine when there is a completed measurement with valid results that can be fetched. If you look for a continuously armed measurement with valid results that can be fetched using INITiate:DONE? then you are unlikely to get anything but WAIT. Each time the Test Set is queried, it is 99% likely to be making another measurement. Even if it did return a measurement name, by the time the control program determines which FETCh? query to send, it is too late to fetch the results and the FETCh? query just hangs until the next measurement cycle is done, nullifying the efficiency provided by the INITiate:DONE? query. |
Pressing the Start Single key on the front panel starts all measurements or measurement suites that have their Trigger Arm parameter set to single trigger mode.
It is unnecessary for you to arm a measurement if the trigger arm is set to continuous. When in continuous mode, the measurement is automatically rearmed after completing a measurement.
Trigger Arm Default Settings
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Action |
Trigger Arm Default Setting |
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Power up of test set |
Continuous |
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Front Panel Full Preset |
Continuous |
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*RST (Remote) Full Preset |
Single |
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Partial Preset |
No change |
SCPI command: SETup:<measurement mnemonic>:CONTinuous[?]
Trigger delay controls the delay time between the trigger and the start of sampling. Resolution is 1 nanosecond per measurement and the units are in seconds. A negative value indicates the sampling should occur prior to the trigger. The default is zero seconds which is preferred for most measurements. If the trigger source is set to immediate any trigger delay setting is ignored.
SCPI command: SETup:<measurement mnemonic>:TRIGger:DELay[?]
Trigger qualifier is only available for the GSM/GPRS/EGPRS Power and Modulation Quality measurement suite. When the trigger qualifier is on, the test set samples the input signal when a trigger is received. It then determines if the input signal was valid by looking at its power level. If the power level during sampling did not meet the requirements of a valid signal, the state returns to wait for trigger without processing the samples.
If a valid signal is present, then it is qualified, and the samples are processed.
SCPI command: SETup:PMODulation:TRIGger:QUALifier[?]
This parameter sets the level below the maximum power level at which the measurement triggers. That is, the trigger threshold is the offset below the Expected Power plus the Amplitude Offset value. This parameter only applies if the Trigger Source is set to Rise. Trigger threshold is not available for every measurement.
SCPI command: SETup:<measurement mnemonic>:TRIGger:THReshold[?]
