Signal subtraction

[nkokras]

Is it possible in a Clarity station with two detectors to subtract in real time one detector signal from the other?

[Daniel Mentlik]

Dear Nikolaos,
this is currently possible only using a workaround in stations that have LC Control or GC Control option enabled (not for stations that solely use A/D converters). Sample rate of the detectors being subtracted should be the same.

To display the signal difference, enter the configuration and add Knauer Virtual Detector on the Instrument in question. Later in the method, you may specify the signal contents for the Knauer Virtual Detector, and you may use other detector signals as source of the data:

You need to set the equation to the desired formula (x-y) and specify the sources of the X and Y parameters as Ext. Source and selecting the particular signal to use. On top of that, on the first tab, change the Time Constant to 0 (basically a averaging data filter) and instead of the sample rate drop-down menu you should be able to freely edit the proper sample rate (make it same as both detectors):

Please note this will not work in Demo mode, the signal of the Virtual Detector in DEMO mode is hard-coded to a set values regardless of the settings in the method.

[nkokras]

Yes, this is exactly what I had in mind. But LC control is sold separately, right?

[Daniel Mentlik]

LC Control (p/n A24) is an optional module sold independently on the basic Clarity (p/n C50). You need LC Control in order to be able to collect digital data from HPLC detectors, directly control pumps, valves, fraction collectors etc. Please send us the serial number of the station (can be found using the Help - About... menu from main station window) to support@dataapex.com and we can tell you whether your station contains LC Control module or not.

[nkokras]

Will do, thank you

[nkokras]

Can I see a screenshot of the advanced settings as well?
Thank you

[Daniel Mentlik]

Advanced settings tab does not have any connection to the desired feature, Virtual Detector is quite generic tool for generating a signal and Advanced tab allows to set custom signal course, such as from minute 0 to minute 1 signal should be 0, from minute 1 to minute 2 it should be 1.28, ...