GB581276A - Improvements in or relating to apparatus for testing or comparing potentiometers or other similar instruments - Google Patents

Abstract

581,276. Testing and calibrating instruments; variable contact resistances. STURGESS, L. O. Dec. 30, 1944, No. 26190. [Classes 37 and 38(i)] An arrangement for comparing a potentiometer or the like with a standard instrument provides for simultaneous adjustment of both instruments, which are connected in parallel across an A.C. source. Any out of balance voltage between the respective moving elements is applied to an amplifier and registered on a cathode ray tube. The potentiometer 56, Fig. 1, under test is attached to the plate 58 and its spindle gripped in the collet chuck 15 formed in the hollow shaft 11, which may be rotated by means of the worm wheel 27 and the worm 28 on the cross-shaft 29 carrying an operating knob (not shown). Also attached to the shaft 11 is the indicating pointer 69 and an insulating bush 35 carrying the radial arm 33 of the standard potentiometer, which comprises the disc 30 bearing a single turn of insulated resistance wire 31 about its circumference. The disc 30 is attached to a worm wheel and sleeve 22 running on the shaft 11, and may be adjusted in angular position by means of the cross-shaft 24 and worm 23. The resistance wire 31, Fig. 2, is attached by soldering at the one end to the terminal block 40 secured to the insulating insert 30a, and at the other to the slidable tensioning member 39 held by the screw 41. The adjustable spring connector 43 is attached to the block 44 which slides under the guide 45 and is adjusted by means of the -screw 46. Connection with the slider 32 is made by means of a coil spring 36. The standard potentiometer 31, Fig. 4, and potentiometer 55 under test are connected in parallel to the terminals 49, 50, to which an A.C. source is connected. The respective sliders 32, 57 are connected via the terminals 53, 54 to an A.C. amplifier 60 whose output is applied to the plates 61, 62 of the C.R.T. 63. The screen 64 of the tube 63 may bear calibrating lines 65, 66 indicating the maximum permissible difference between the outputs of the potentiometers 31, 35.