PicoQuant GmbH HydraHarp 400 Software V. 3.0.0.1
Zero Cross edit box and spin control
Here the zero cross level of the Constant Fraction Discriminator (CFD) for the Input Channels 1…4 can be set.
Units are millivolts (mV), the permitted range is 0 to 40. Type the value as an integer in the edit box and press
<Enter> or click on Apply. Alternatively, use the spin control (next to it) to increment / decrement the current
value. In this case changes take effect immediately without pressing <Enter>.
Discriminator Level edit box and spin control
Here the discriminator level of the Constant Fraction Discriminator (CFD) for the respective input channel can
be set. Units are millivolts (mV), the permitted range is 0 to 1,000. This corresponds to real input voltage levels
of 0 to −1,000 mV. Type the value as an integer in the edit box and press <Enter> or click on Apply.
Alternatively, use the spin control (next to it) to increment / decrement the current value. In this case changes
take effect immediately without pressing <Enter>.
Offset edit box and spin control
Shifts the relative timing of photon events and is designed to compensate optical and electrical delays (e.g. in
cables and optical paths), e.g. in order to shift your fluorescence decay within the sync frame so that it is not
truncated. This feature completely eliminates the need for adjustable delay boxes.
Units are picoseconds (ps), the permitted range is from −99,999 ps to +99,999 ps. Type the value as an integer
in the edit box and press <Enter> or click on Apply. The offset value can be entered in steps of picoseconds.
Alternatively, use the spin control next to the edit box to increment ⁄ decrement the current value. In this case
changes take effect immediately without pressing <Enter>.
All=Ch1 group of tickboxes
On the right hand side of the regular controls there is a special group "All=Ch1" with three tick boxes labelled
"ZeroCr.", "Disrc." and "Offset". When one of these is ticked, control of this parameter is coupled to the
corresponding input setting for channel 1. All other channels will automatically take the same setting. This
serves as a means of manipulating all channels at once, which can be helpful in the initial setup phase when
there are a lot of channels that must be brought to identical standard settings. Later, when individual fine tuning
is required, the tick can be removed and the individual channels can then be programmed individually again.
Note that removing the tick does not bring the previous individual settings back. If you have lost some specially
optimized settings you may load a data file with known good settings which will update the control panel
accordingly. It is therefore a good idea to save a data file after optimizations have been completed and name it
descriptively as something like "initial settings for experiment X".
6.4.3. Inputs 5…8
This page only exists when more than 4 input channels are installed. It has the same controls as the page for
inputs 1...4 and follows the same logic of operation (as described above).
6.4.4. Acquisition
Resolution edit box and spin control
Use this set of input controls to specify the acquisition resolution. Units are Picoseconds (ps). Possible choices
are the base resolution (1 ps) and binary multiples of this resolution (1, 2, 4, 8, 16, … ps). Type the desired
resolution value (ps) as an integer in the edit box and press <Enter> or click on Apply. Alternatively, use the
spin control (next to it) to increment / decrement the current value. In this case, changes take effect
immediately without pressing <Enter>. In case of entering values other than valid resolutions, the next
suitable resolution step is chosen automatically.
There are always 2
16
= 65,536 channels in one histogram. With the different resolutions, the approximate time
ranges covered are between 65,536 * 1 ps = 65.5 ns up to 65,536 * 33,554,432 ps = 2.199 s. The choice of
range must compromise between resolution and time span covered. The smallest range offers the best
resolution and the shortest span (vice versa for the largest range). For sync rates > 20 MHz the highest
resolution is usually most appropriate, since the smallest range still covers the full sync period. For lower sync
rates the histogram range is too small to cover the full sync period. The decay curve region of interest may
therefore lie outside the acquisition window of 65,536 time bins. Apart from switching to a lower resolution it is
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