Cornelius DPC 230 Specifications download pdf (Page 24)

18 Operating the DPC-230

Manufacturer Type Pulse Pulse Remark

Amplitude Width

id Quantique id 100-xx +2 V 20 ns Versions of different area available

MPD PDM-xxCT +2 V 20 ns Use TTL output. Versions of different area available

Perkin Elmer SPCM-AQR +3.5 V 35 ns

Hamamatsu H7421-40 +3V 30 ns GaAsP PMT module, QE = 40% at 500nm, large area

When using LVTTL- or TTL-compatible detectors, please make sure that the corresponding

DPC-230 input is configured for ‘rising edge’, see ‘Configuring the Inputs’ page 46.

Synchronisation to Light Sources via the LVTTL Inputs

When operated in the multichannel-scaler mode the DPC-230 needs a timing reference signal

from the light source. Pulses from commonly used PIN or avalanche photodiode modules are

usually not LVTTL-compatible. If the DPC has to be synchronised via a photodiode the circuit

shown in Fig. 22 can be used.

Photodiode

Fast PIN

+5V

100n

To DPC-230,

LVTTL Input

Fig. 22: Generating an LVTTL-compatible trigger signal via a PIN photodiode

Marker Pulses

Marker pulses can be used to identify external actions within the data stream delivered by the

DPC. Typical examples are pixel and line synchronisation pulses of a scanner. Marker pulses

can be connected to any LVTTL input that is not used for a detector. The pulses should be

LVTTL or TTL. Please note that only the low-high or the high-low transition of the signal

appears in the data. Thus, make sure that the DPC inputs are correctly configured, see

‘Configuring the Inputs’ page 46.

CFD Inputs

The DPC-230 has four CFD (constant fraction discriminator) inputs. These inputs are de-

signed to trigger on single-photon pulses of PMTs. For best high-frequency behaviour, SMA

connectors are used. CFD The CFD inputs are shown in Fig. 23.

Fig. 23: CFD inputs

The pulse amplitudes at the CFD inputs should be negative and within a range of -50 mV to

-500 mV.

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Cornelius DPC 230 Specifications Page 24