iSource
®
StarLPRO-1500
Manual
©SpectraTime
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North America Sales Offices
Page 8 of 12
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Fig. 2-4: STARLPRO-1500 block diagram
The C-field coil within the physics package generates a magnetic field necessary for Rb spectral lines
separation. This magnetic field allows fine tuning of the 10MHz output frequency by shifting the Rb frequency
hyperfine transition by the second-order Zeeman effect.
A high stability current generator drives this coil; it is adjustable by the user in order to attain a fine analog or
numerical resolution via a digital-to-analog converter.
The user interface consists of the RS-232 port for the monitoring of the internal parameters and for the center
frequency adjustment. In addition, an analog frequency control input is available to the user for center
frequency adjustment by external potentiometer or external digital to analog converter.
The correct operation of the unit can be checked by a single open collector type output signal called ‘ lock
monitor’. This lock monitor information is generated by the micro-controller and is a function of the following
parameters:- Light level intensity
- Rb signal level (detected signal)
- Heaters supply voltages
- RF section health.
The different alarm threshold levels corresponding to the different internal STARLPRO-1500 electronics and
physics parameters are programmed during the automatic adjustment procedure at the factory.
The power section of the STARLPRO-1500 consists of three dc-dc converters. One is used for generating the
internal 5V needed by the logic circuitry, the two other converters are used for the lamp and the cell heaters.
The synchronization of the three converters is achieved by the use of a common ramp generator given by an
internal 156.25 kHz signal derived by direct division of the 10 MHz main VCXO.
A detailed block diagram of the STARLPRO-1500 is given by Fig. 2-4.
