Data acquisition system for the measurements of corona currents

The measurements of voltage-current relationships in gas discharge systems often require special equipment not readily available on the market. In the presented study, a data requisition system is described, which was used for the measurements of corona currents in a pin-plane corona generator of the array type, with pins negative. The pins were made of tungsten and were arranged in two rows. The ground plane was planar, made of aluminum, and equipped with circular current-sensing electrodes made of brass and insulated from the planar anode with teflon rings. Each of the sensing electrodes was connected to 50 k/spl Omega/ resistor. The voltage across each of the resistors was measured with an operational amplifier circuit. The output of the operational amplifier was connected to an electronic scanner, the output of which was used as the input for a microcontroller (HC11, Motorola). The microcontroller was connected via the RS 232 link to an interfacing board inserted into the PCI bus of a personal computer. The computer provided a graphical user interface was used to store and process the collected data, and supported the popular data processing programs. The system allowed the measurements of the current magnitudes on up to sixteen corona pin, simultaneously. The computer interfacing board can parse the data into up to eight separate data streams. The data acquisition unit can be configured to operate with four, eight, or sixteen input channels, trading their number for the sampling rate and frequency response in three steps: 4 channels, 16,000 samples.s/sup -1/; 8 kHz; 8 channels, 8,000 samples.s/sup -1/, 4 kHz; 16 channels, 4,000 samples.s/sup -1/, 2 kHz. In the described experiment, the system was set to sample four simultaneous data streams and provided adequate response. The system operated at the same ground level as the high voltage ground. The cost of the parts used in the unit is approximately fifty dollars. With an appropriate set of sensors, the unit can be used in other high voltage applications.