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Description: | 230-250 V A.C. 150 C.P. ( operating voltage range and power of the lamp in Candles). EDISWAN 150 CP A.C. POINTOLITE RESISTANCE (trade name and model on an aluminium plate on the base of the unit). WORKING INSTRUCTIONS TURN SWITCH TO POSITION 1 AND WAIT FOR 3 SECONDS TURN TO POSITION 2 WAIT FOR 5 SECONDS AND THEN TURN TO POSITION 3. ON NO ACCOUNT MUST SWITCH BE MAINTAINED IN POSITION 1 OR 2 LONGER THAN THE SPECIFIED PERIOD. (manufacturer's operating instructions on an aluminium plate on the base of the unit). MADE IN ENGLAND (on an aluminium plate on the base of the unit). DES The Edison Swan Electric Company Limited. circa 1915 Head Office, 155, Charing Cross Road, London, W.C.2.
Works, Ponders End, Middlesex. England MANU Santon Limited. circa 1935 Newport, England This is a ballast resistance or starter unit for a Pointolite arc lamp. The unit consists of a simple resistance coil with a single tap and a four pole switch. The Pointolite lamp was a discharge tube that used the incandescence of tungsten ball electrodes. Negligible light was generated by the gas discharge. The lamps were usually made for operation using direct current and the electrodes were in the form of tungsten beads, between which a direct current arc passed. This ballast resistance was made for alternating current operation. The bulb was filled with a low pressure nitrogen-helium mixture and the arc was struck between two tungsten beads.
For ignition purposes, a seven volt tungsten filament was streched at right angles between and below two tungsten bead electrodes. There was a fine 'ioniser' tube of thorium oxide slipped over one end of the filament. An arc was initiated by turning the switch to P1, this connected the filament to the tap on the resistance that allowed sufficient current to make the filament incandesce, which in turn generated free electrons around the ioniser tube. After 3 seconds sufficient electrons had been produced and P2 was selected. This connected the tungsten electrodes to the tap and arc was struck between the filament and one of the electrodes. Once the first tungsten bead electrode was incandescent then the current established an arc across both beads and both became fully incandescent after 5 seconds. When this occurred P3 was selected whereby a current, just sufficient to maitain the arc, was applied by connecting the electrodes to the full resistance. At the same time the voltage to the filament was switched off to prevent overheating. P4 was the off position when no current passed through the lamp. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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