GB1303124A - - Google Patents

Abstract

1303124 Electro-physical measurement - dimensions MESSER GRIESHEIM GmbH 19 March 1970 [19 March 1969] 13334/70 Heading G1N [Also in Division G3] In a capacitance probe for measuring the distance of e.g. a plasma-torch above the edge of a work-piece (forming the earth electrode), the probe is split into a plurality of electrodes connected to a circuit to DETECT AND PASS ON the HIGHEST capacitance VALUE, (thereby ignoring false readings from electrodes over the edge). This maximum value is used to control the torch positioning servomotor. Fig.1 provides continuous measurement and control. Electrodes 1..4 tune oscillators 6.. 9 connected to discriminators 10..13. Relative signal magnitudes of the pairs 1, 2, and 3, 4 are determined by comparators 18, 19 energizing polarity sensitive relays 20, 21. The relative magnitude of the two signals thus passed on is determined by a similar comparator relay circuit energise the distance controlling servomotor 30. Alternatively Fig.2 provides sequential testing of the electrodes and a timed control period. A counter 114 sequentially pulses oscillators 6'.. 9' connected in parallel to a discriminator 110 whose output is fed into a peak-value-store 113. The sixth count triggers flip-flop 117 to throw switch 112 so that the next cycle of oscillator/discriminator outputs is fed to comparator 119, to find the maximum signal equal to the stored peak. This triggers monostable circuit 122 to stop the counter and feed the maximum signal to the servo-system 29, 30 for a time depending on the constant of the monostable circuit after which the above cycles are repeated.