Fast Data Acquisition

Fast data acquisition refers mainly to the radiometers and the correlator square-law detector. The radiometers are interfaced via two digital voltmeters (DVMs) which can be switched to take any of the radiometer outputs or various other sources as inputs. The DVMs are currently Fluke 8840A's which are interfaced via HPIB. The most stringent requirement is that they have to be read synchronously with the telescope positions and correctly time-stamped. Synchronization has to be to within a few milliseconds. The sampling frequency on the old system was a maximum of 50 Hz. The NCCS must be capable of guaranteeing this as well.

The most logical place to read the DVM's is to do so in PC-STEER. This is because PC-STEER has the telescope coordinates and time locally available.

The acquisition system must offer standard data treatment options for the radiometer readings e.g. averaging, median filtering.

The HPIB-based DVMs are 9 years old and showing signs of aging - they should be replaced as standard continuum data acquisition DVMs. The DVMs could be replaced either with new intelligent DVMs á la Fluke's or with A/D interfaced directly to a PC.