Trigger  

 

Instrument Type:

System Command

Related Commands:

EndTrigger

Description:

Executes all commands in the trigger block if the given conditions become true; for example, if a signal exceeds a specified threshold. Use the Condition parameter to define the condition(s).

In the program, the entire Trigger block is indicated in blue color.

Examples

  • A typical use for this function is the control of a Fraction Collector. If the absorption signal of a given channel exceeds a threshold value, a relay is enabled, switching to the next collection vial. Further important applications are:

 

  • Signal-dependent Wavelength Switchings; for example, immediately after completion of a peak. Thus, retention time variations can be neglected.

 

  • Programs can be Branched off according to external conditions, such as a remote input or the value of an analog signal. Thus, you are flexible in determining the chromatographic reaction to external conditions (pressure, conductivity, etc.).

 

  • Acoustic signals can be generated when certain conditions become true (Sound). Thus, your peaks can be made audible.

    Note:

    Windows XP (64 bit), Windows Vista and Windows 7 operating systems do not support the Sound command.

Function:

The trigger condition is continuously activated once the trigger has been defined and has to be specifically disabled if it is no longer needed. However, signal values are received only after the AcqOn command of the program. The commands in the trigger block are executed every time the specified conditions change (edge triggering), i.e., upon each transition from false to true.

 

As a response to a trigger condition becoming true, virtually any instruction can be performed. Examples:

  • AbortBatch

  • Acquisition.on/off

  • Branch

  • Log

  • Message

  • Protocol

  • Relayname.on/off

  • Signalname.Parameter

  • Sound

Triggering the flow rate and the solvent composition is also possible. However, a gradient will be interrupted, and the analysis will be continued under isocratic conditions. Yet, you can use the Branch command to start a new gradient program.

Note that trigger commands can be triggered, also.

For examples, refer to  Trigger Commands.

Parameters:

 

Name

The name of the trigger command is obligatory. It serves for its identification. That is why the name must be unique, that is, the trigger cannot have the same name as a device or another command.Several triggers with different names can be activated simultaneously.

 Note:

To be able to find the trigger in an Audit Trail or a Report, it is recommended to include the trigger name in capital letters in the program.

Condition

Defines the trigger condition and can have two forms:

 

<Parameter><Comparison Operator><Value> or
<Signal.Delta><Comparison Operator><Value>

 

or

 

<Remote-Input-Name>

 

<Parameter>
All installed channels, but also parameters such as Temperature (column temperature), Pressure (system pressure), Flow (flow rate), and %A, %B, %C, and %D can be used.

<Signal.Delta>
For signals, the first derivative of the parameter can be evaluated. This is achieved by adding the signal property Delta.

<Comparison Operator>
<, >, =, <=, >= and <>

<Value>
Fixed-point number. The dimension of the <Value> corresponds to the signal dimension. Parameters that are combined with Delta have the dimension [signal dimension / s].

<Remote-Input-Name>
is reported from the instrument to Chromeleon, for example, Sample.Ready or Leak.

 

If several parameters are to be linked, this can be realized via arithmetical (+, -, *, / , **) or logical (AND, OR, NOT, XOR) operators. Parentheses show combinations and hierarchy, as for instance:

 

  • (UV_VIS_1>100) AND (UV_VIS_2>100)

 

  • (UV_VIS_1+UV_VIS_2)>200

 

It is also possible to logically combine entire conditions.

 

  • (UV_VIS_1>100) AND NOT (UV_VIS_2>200)

True

Validity in seconds. The trigger condition must be true for this time to activate the trigger. Example:

 

Trigger DIGIN1 Remote1, True=2.0

 

The input signal must be active for at least 2 seconds to trigger DIGIN1.

The True parameter can also be used as a criterion for signals; for example, to differentiate between true signals and spikes.

After activation of the trigger, the True parameter is also used as "False" time. This means that the trigger can be activated only after the "True" time condition has become false.

Delay

Indicates the delay time (in seconds) between fulfillment of the conditions and execution of the command; for example:

 

1.220 Trigger SIGNAL UV_VIS_1>20, Delay=5.0

 

FracCol.on

 

EndTrigger

 

The FracCol relay is switched 5 seconds after the condition becomes true.

The Delay parameter is usually used for switching a fraction collector with a time delay. Thus, the dead volume between the detector and the fraction collector can be taken into account.

If the Delay parameter is used in combination with the True parameter, the command is executed only <TRUE> + <DELAY> seconds after the condition is true.

Limit

The upper limit for executing the trigger command. Without the limit parameter, a trigger command is carried out any number of times until the trigger is deleted. The limit parameter automatically deletes the trigger after a corresponding number of activations. Example:

 

1.220 Trigger BRANCH RemoteIn, Limit=1

 

Branch NEWPGM

 

EndTrigger

 

The trigger command is only carried out once, and then the trigger is deleted.

Hysteresis

To prevent multiple trigger execution with very noisy signals, each trigger receives the Hysteresis parameter in addition to the True parameter.

In contrast to the True parameter, Hysteresis is not time but signal-dependent. The parameter can vary between 0 and 100%. The default value is 5%.

A 5 % hysteresis causes, for example, the condition

UV_VIS_1 > 20,0

to change from FALSE to TRUE when reaching the value 20.0, but only changing from TRUE to FALSE at 19.0. Thus, a difference is made between signal increases and decreases. This corresponds to the different paths of a hysteresis loop.

If the operator < is used instead of >, the calculation is reversed! For the above example this means that the condition

UV_VIS_1 < 20,0

becomes TRUE immediately when the value falls below 20, but is reset from TRUE to FALSE only at 20 + 5% = 21.

 Tips:

While acquisition is disabled or interrupted, signal values cannot be evaluated.

 

If the True and Delay parameters are used, the trigger block is executed only <TRUE> + <DELAY> seconds after the condition becomes true.

 

End program automatically deletes all triggers.

 

Triggering the Flow, %B, %C, and %D commands is restricted to isocratic separations.

 

For certain instruments, the settings cannot be changed during the sample run. Thus, it may happen that trigger commands are not performed.

 

Example:

 

When the trigger condition becomes true, the following program switches the flow to 0.1 ml/min and sets %B to 0.

 

-1.000 Trigger ELUENT UV_VIS_1 > 20

 

       Flow = 0.100

 

       %B.Value = 0.0

 

       EndTrigger

 

0.000  Inject

 

0.000  UV_VIS_1.AcqOn

 

....   ........

 

15.000 UV_VIS_1.AcqOff

 

15.000 End