TRIGger:SOURce
Syntax
TRIGger:SOURce <source>
TRIGger:SOURce?
Description
This command selects the trigger source for measurements. The instrument will accept an immediate (continuous) trigger, a software (bus) command, an external TTL trigger pulse, an alarm-initiated action, or an internally-paced timer. The front-panel sample annunciator ( "*" ) turns on during each measurement.
Used With:
34921A through 34925A Multiplexer Modules
34950A Digital I/O Module (digital input and counter channels only)
34952A Multifunction Module (digital input and totalizer channels only)
Parameters
|
Name |
Type |
Range of Values |
Default Value |
|
<source> |
Discrete |
{IMMediate|BUS|EXTernal|ALARm1|ALARm2|ALARm3|ALARm4|TIMer} |
IMMediate (continuous) |
Remarks
When making measurements independent of any channels or a scan list, this command selects the trigger source for the internal DMM.
When using channels and a scan list, this command controls the onset of each sweep through the scan list (a sweep is one pass through the scan list). The selected source is used for all channels in the scan list.
After selecting the trigger source, you must place the internal DMM in the "wait-for-trigger" state using the INITiate or READ? command. A trigger will not be accepted from the selected trigger source until the internal DMM is in the "wait-for-trigger" state.
For the IMMediate (continuous) source, the trigger signal is always present. When you place the internal DMM is in the "wait-for-trigger" state, the trigger is issued immediately.
For the BUS (software) source, the internal DMM is triggered by the *TRG command received over the remote interface. The *TRG command will not be accepted unless the internal DMM is in the "wait-for-trigger" state (see INITiate command). If the internal DMM receives an external trigger before the next "waiting for trigger" state, it will buffer one *TRG command and then ignore any additional triggers received (no error is generated).
For the EXTernal source, the internal DMM will accept a hardware trigger applied to the rear-panel Ext Trig Input line (Pin 6). The internal DMM takes one reading, or the specified number of readings (sample count), each time a low-true TTL pulse is received. If the internal DMM receives an external trigger but is not in the "wait-for-trigger" state, it will buffer one trigger and then ignore any additional triggers received (no error is generated).
For the ALARmx source, the internal DMM is triggered each time a reading crosses an alarm limit on a channel. See the OUTPut:ALARm<n>:SOURce command for more information. With this source, you can use the Monitor mode (see ROUTe:MONitor:STATe command) to continuously take readings on a selected channel and wait for an alarm on that channel. Channels do not have to be part of the active scan list to be monitored; however, the channel must be configured for a measurement in order to be monitored. Use the TRIGger:SOURce:ALARm[:MODE] command to control the behavior of the scan when an alarm condition is detected (single or continuous).
For the TIMer source, you control the trigger-to-trigger interval (in seconds) for measurements on the channels in the present scan list. Use the TRIGger:TIMer command to set the wait period.
Although the TRIGger:SOURce command shares some of the same signals as the ROUTe:CHANnel:ADVance:SOURce command (used for external scanning), they cannot be set to the same source (except IMMediate). If you attempt to select the same source, an error is generated and the TRIGger:SOURce is reset to IMMediate.
The CONFigure and MEASure? commands automatically set the trigger source to IMMediate.
The instrument clears all readings from memory when the triggering configuration is changed.
The instrument selects the immediate trigger source after a Factory Reset (*RST command). An Instrument Preset (SYSTem:PRESet command) or Card Reset (SYSTem:CPON command) does not change the setting.
Return Format
The query command returns the present trigger source: "IMM", "BUS", "EXT", "ALAR1", "ALAR2", "ALAR3", "ALAR4", or "TIM".
Examples
The following program segment selects the external trigger source. In this configuration, the instrument sweeps through the scan list once each time a low-true TTL pulse is received on the rear-panel Ext Trig Input line (Pin 6).
TRIG:SOUR EXT INIT
The following program segment selects the bus (software) trigger source. Note that the *TRG command will not be accepted unless the internal DMM is in the "wait-for-trigger" state.
TRIG:SOUR
BUS
INIT
*TRG
The following program segment selects the alarm source and configures the instrument to scan when an alarm is reported on Alarm 1. The Monitor mode is used to evaluate alarm conditions on the selected channel.
TRIG:SOUR
ALARM1 !Select
trigger source
TRIG:SOUR:ALARM CONT !Select
continuous scan mode
CALC:LIM:UPP 10.25,(@1003) !Set
upper alarm limit
CALC:LIM:UPP:STAT ON,(@1003) !Enable
alarms
OUTP:ALARM1:SOUR (@1003) !Report
alarms on Alarm 1
ROUT:MON:CHAN (@1003) !Select
monitor channel
ROUT:MON:CHAN:ENAB ON, (@1003) !Enable
monitoring on selected channel
ROUT:MON:STAT ON !Enable
monitor mode
INIT
The following program segment selects the timer source and sets the scan interval to 30 milliseconds.
TRIG:SOUR
TIMER !Select
trigger source
TRIG:TIM 30E-03 !Scan
interval is 30 ms
INIT
The following query returns the trigger source currently selected.
TRIG:SOUR?
Typical Response: EXT