auto exposure time too high

<p><span>Hi everybody,</span></p><p><span>Can anyone tell me what does this warning message :"<strong>The autoexposure time is too high</strong>" means? I found it after starting a sample set on my UPLC. </span></p><p><span>If it can help, the Instrument method has these parameters:</span></p><p><span>Exposure time: auto</span></p><p><span>Filter time constant: fast</span></p><p><span>Sampling rate: 20 points/sec</span></p><p><span>Thank you very much,</span></p><p><span>Lorenzo</span></p>


  • lizh

    Autoexxposure is the automatically determines the correct rate (in millisecs) of scanning the diode array, to get losts of energy to reduce noise but does not wait too long and the diode saturate. The diods are scanned, there is a wait time as the diodes collect the light energy signal after it comes through the flow cell. We do this so that the noise is never an issue, it will gradually reduce as your lamp ages. is going to be longer This is very diagnostic. In results you should see for a given mobile phase and a given sample set autoexposure value remains the same, but it will be longer for example, for a TFA mobile phase whcih absorbs light.

    You get this message it takes too long and saturation of the diodes or simply that there is too little energy.

    So listing this in order, the most common cause would be that there was "something" such as a air bubble in the flow cell. Then upon powerup when the Autozero is set up and calculated it could possibly set up a very high exposure time thus triggering the message. Please check/ remember that the mobile phase should be filtered, degassed, and free of any air bubbles and flowing through the flow cell before you turn on the detector.

    After ensuring this is the case and the error still occurs repeatedly then we would have to look at other hardware issues to isolate the root cause. From experience it is usually something

    within the flow cell...again check the flow cell contents, go to a simple mobile phase and see what happens. Then please check under normal conditions and verify what the energy transmission is at 230nm from the “READ ENERGY” screen in the console.

    Thank you,


  • I was told by Waters tech support after several phone calls that this is a glitch in the firmware and that it would be corrected when the new version comes out.