Patent GB-711608-A (GB)
Title: Improvements in or relating to disappearing filament pyrometers
IPC: G01J5/52
Filed: 1951-07-02
Abstract: 711,608. Optical pyrometers. TINSLEY (INDUSTRIAL INSTRUMENTS), Ltd., and KERSHAW, P. L. July 2, 1952 [July 2, 1951], No. 15641/51. Class 97(3) A disappearing filament pyrometer in which the brightness of an object whose temperature'is to be measured is compared with that of an incandescent lamp filament which is included in a bridge circuit so that variations in lamp resistance can be used to indicate the object's temperature and in which an operating member is connectable to the lamp current adjusting means and to the bridge adjustment means simultaneously so that the bridge is automatically maintained approximately in balance as the lamp current is adjusted and is disconnectable from the lamp current adjustment means so that further movement of the operating member after the lamp current has been adjusted can be used to bring the bridge to precise balance, comprises a slide wire along which can move for adjusting the bridge a galvanometer terminal carried by the operating member, and a rheostat for adjusting the lamp current, the movable contact of which rheostat is carried by a member normally disconnected from the operating member but engageable therewith by an axial movement of the operating member so that, on moving the operating member axially and then rotating it, the movable rheostat contact and the galvanometer terminal can be moved simultaneously to match the lamp brightness with that of the object after which the operating member can be withdrawn to disengage the member carrying the rheostat contact so that further rotation of the operating member moves the galvanometer terminal alone until the bridge is accurately balanced. The pyrometer shown comprises a case 3 accommodating an objective lens 35 for imaging an object on an incandescent lamp 49 and an eyepiece system for observing the lamp and the image, this system being housed in a sleeve 6 carried by a plate 2 within the case. Lamp 49 is connected through a battery and a switch, with brushes 17, 18 on a member 16 rotatable round sleeve 6, these brushes being respectively engaged with a collector ring 19 and a rheostat 4 on the plate 2. The latter also carries a slide wire 1 engaged by a brush 15 on a disc 12 which also carries a collector ring 13 connected through a brush 14 with a galvanometer 24, and a temperature scale 32 which may be viewed through a window 33. Disc 12 is rotatably mounted on the sleeve 6 and may be moved axially thereof by a knob 8 so that clutch parts 20, 21 on the disc and member 16 engage. Rotation of the disc 12 when in this position thus adjusts the rheostat 4 to match the lamp brightness with that of the object and also adjusts the slide wire 1 so that a bridge, of which the slide wire and lamp form parts, is maintained approximately in balance. When the lamp brightness has been correctly matched, the disc 12 is withdrawn and again rotated to adjust the slide wire 1 alone and accurately balance the bridge. Filters 39 in a rotatable shutter 40 are provided to allow of a range change. A pin 31 is slidable in plate 2 and is moved axially, when the disc 12 is moved to engage the clutch 20, 21, to remove a latch 26 so that the battery switch key 29 can be closed. A similar pin at the same time opens a switch in circuit with the galvanometer. Reference has been directed by the Comptroller to Specification 636,544.