1. NSGF 2000 PICO EVENT TIMER HERSTMONCEUX SLR STATION

2.  Here at Herstmonceux we have used the commercially available Modules from Thales Systems.  The Timing System has been designed using 3 Modules: Two Timing Modules and One Clock Module.  This is all we need for a simple START/STOP System.

3.  A special input board has been designed to enable our ranging PC to control the selection of 3 different types of start input signals and 2 further inputs to each module: 1-pps and 1-KHz pulses.  The 1-pps is applied to both timing modules, allowing epoch synchronisation.

4.  The 1-KHz pulses are to determine the offsets between the modules.  All modules are to be connected to, and controlled by, our Ranging PC via a 96-bit DIO interface.

5. HARDWARE  Should not degrade the specification of the modules;  2 modules required as minimum for start/stop time intervals;  Should allow for independent Epoch Timing &/OR Time Interval Measurements;  Automatic Epoch Reference via 1-pps pulses from external GPS reference;

6.  Automatic Internal Offset Determination between Modules;  PC interface should not affect the maximum repetition rate of 2.0KHz;  PC should not degrade the high resolution of the modules

7. The Input Board  Main goal not to degrade the Thales modules specification;  Careful design of Input Board;  Separate GND and Power Supplies for the different parts;  Use of Opto-Couplers for logic control by ranging PC.

8. The input board has to:  Handle, switch and enable 3 types of pulses  Input Pulses:  Start pulses (NIM/TTL etc) from laser and stop pulse from the C-SPAD  1-pps pulse from GPS  1 KHz pulses on-board the PCB  Output Pulse:  Standard ECL into 50Ω @ -2Volts

9. Power Supplies  Separate power supplies for each module.  8-Euro-Card size power supply units optimised for it’s specific purpose.  Forced air cooling to remove heat from these power supplies.

10. Ranging PC 96-bit DIO 8 Power Supplies Module 1 Module 2 Clock Module Input Board NSGF 2000 Pico Event Timer 96 Fig.1: General Setup Block Diagram

11. + + - - Module 1 Module 2 Clock Module Hx GPS 1 KHz Pulses for Module Offset Cal 1 pps from GPS For Epoch Ref 10 MHz1 pps START STOP PC Control Input Select Module Read Module Write PC Control Principle of Input Board Fig. 2: Principle of Input Board