Special Commands, Relay Control, and Miscellaneous
Program Examples for Virtual Channels

Examples:

Changing the Channel Type

The Virtual Channel Driver allows to assign each virtual channel a default type during installation. Three types are currently defined, see  Configuring the Channels of the Virtual Channel Driver in the Administrator Help section. However, you can specify a different channel type in the program.

Recording the Pump Pressure

You can use the Virtual Channel Driver to record the pump pressure. This steady signal is likely to change frequently. That is why Dionex recommends setting the type of the virtual channel to Analog. You can use the default settings for recording this channel:

The signals are recorded at the intervals determined by the corresponding pump. The intervals might be too large to return the pump pressure precisely. In this case, use the Integrator Driver to receive the precise pump pressure signal. In this case, you will need an A/D converter such as the UCI-100 Universal Chromatography Interface and a pump that outputs the pressure at the analog output (also, refer to  Recording the Pump Pressure).

Recording the Temperature with a Thermometer

Before you can use a virtual channel for temperature recording, select TemperatureOVEN.Formula to assign the Temperature_1 thermometer channel. Please note that the name TemperatureOVEN refers to the virtual channel while the reserved name Temperature_1 is the channel name of the thermometer. This is the name accessed by the virtual channel.

The program part below refers to the above configuration:

Sum of two channels

Much as the pump pressure, you can record the sum of two UV channels as a virtual channel. This steady signal is also likely to change frequently. That is why Dionex recommends setting the type of the virtual channel to Analog. Using the default settings, this channel is recorded as precisely as the two UV channels:

 Tip: 

If step gradients occur for virtual signals consisting of other signals even if the channel type is set to Analog, the resolution in y direction is insufficient. In this case, set FormulaMin/FomulaMax accordingly.

Relay Status

The status of a relay should be recorded as a virtual channel. For this rectangle signal, Dionex recommends setting the type of virtual channel to Digital:

Recording a Gradient

The currently set gradient should be recorded as a virtual channel. This steady signal is unlikely to change frequently. That is why Dionex recommends setting the type of the virtual channel to Fixed. It is sufficient to record the current value once per second:

Correcting a signal from a radioactive substance:

To determine the concentration of a radioactive substance, you must take the decay of the substance into account and correct the signal accordingly. Use the virtual channel driver to accomplish this task.

In the example below

The half-life is t½ min

The run time of the chromatogram is tl min

The uncorrected signal (UV_VIS_1) is between - 10.000 and 10.000 mAU,

In the program, replace the t½ entry with the actual half-life. In addition, enter the actual run time of your program with three decimal places for tl.

When the program is modified accordingly, the virtual channel records the signal that would be measured by the detector if the radioactive decay were stopped with the injection into the chromatography system. The decay that occurred before the injection will not be corrected.

 Note:

If you know the signal range to be expected for your chromatogram (in the example for the channel UV_VIS_1) you may enter this value instead of -10,000 and 10,000 for calculating FormulaMin/Max to map your chromatogram more precisely.