>Dear All,
>
>I'm having trouble with the linearity of the readings of our Zeiss LSM
>410.
>
>I have been controlling the PMT and amplifier gain separately, which
>seems to be great because of the linearity of the amplifier gain.

snips

>I contacted Carl Zeiss some time ago, but I haven't got any reply yet.
>
>Does anybody know what may be happening?
>
>Thanks in advance
>
>Carlos

I know nothing about the instrument to which you refer. And I'm not
entirely clear about the details you give.

However, from other experience with PMTs, if the HT bias on the PMT is too
high, its output will become nonlinear. Equally, if you turn it down too
far, you loose sensitivity. So, for optimum performance of a PMT, it is
usually not sufficient to set the PMT HT to some standard value. Somewhere,
there will be a procedure for setting the HT on this unit. This can also
interact with PMT 'dark current', that is, the output from the tube with
zero intensity input.

Hope that might help.

Regards,

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Dr L. P. Stoter          Technical Editor, MICROSCOPY & ANALYSIS
Technesis
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