A new data acquisition system has been developed for the TJ-I tokamak and the TJ-IU torsatron. This system is based on the VME standard and it is controlled by an MC68020 microprocessor. This scheme is similar to the ones existing at CERN and used in high-energy physics experiments. [On-line Computing Group, Valet-Plus Operation Guide, Data handling, CERN DD Division OC Group]. The data acquisition system consists of 60 independent, fully programmable channels. Each channel has its own analog-to-digital converter (ADC) with a resolution of ten bits and a RAM memory of 128 kbytes (kB). A digital-to-analog converter is also included for providing an analog output in order to display the stored signal on oscilloscopes. The maximum sampling rate achievable with the ADC used is 500 Ksamples/s, which is equivalent to a sampling period of 2 mus. Each channel is programmed to have its own sampling period (in 400-ns steps), and to use the amount of storage required according to the sampling period and the pulse length, up to a maximum of 128 kB. The system controls not only the 7680 kB corresponding to the memory of the 60 channels, but a RAM buffer of 4 MB as well. The system is linked to a local ETHERNET network in order to send the recorded data to the disks of a VAX/VMS computer, where the data are available for analysis.
