Patent GB-724093-A (GB)
Title: Improvements in or relating to arrangements for testing electricity meters
Inventor: SHARP FRANK ALLEN
IPC: G01R35/04
Filed: 1952-07-15
Abstract: 724,093. Testing electricity meters. SANGAMO WESTON, Ltd. July 15, 1952 [July 16, 1951], No. 16856/51. Class 37. [Also in Group XL (b)] A method of testing electricity meters comprises generating pulses at a constant frequency proportional to the rated speed of a first meter at a given load and employing the said pulses to operate an indicator device at a rate proportional to said speed and deriving from a second meter start and stop signals which are applied to said indicator device whilst both meters are rotating under steady conditions. The invention is described with reference to testing watthour meters and utilizing photo-electric cells and scale-of-two counting circuits and electromagnetic clutch control of the indicator device. The latter has fast and slow meter-error dials and the correct one is automatically illuminated. General description, Fig. 1.-The slotted-disc constant speed standard S co-operates with lamp/photo-cell 12/17 and amplifier 19 to drive synchronous motor 20 and the latter through gearing 23 rotates shafts 24 at different speeds correctly proportioned to the test loads and test revolutions to be counted so that counters 31, 32 exhibit the error in the test meter T in relation to the standard S as a constant comparison ratio, e.g. percentage fast or slow direct reading as shown. The test load is switched on and (i) counters 31, 32 are zeroized, (ii) the required shaft 24 is coupled by clutch 26 to common shaft 27, (iii) the correct input stage iu a treble scale-of-two pulse divider at 49 is selected so as to determine the test revolutions to be counted. Directly the first anti-creep hole 45 in the test meter T is in line with lamp 42 a start pulse delivered by photo-cell 47 travels quickly through amplifier/divider 49 and clutch control 50 to actuate high-speed clutch 29 so that shaft 27 commences to drive counters 31, 32 from zero. When the meter T has made the chosen test rotation the last anti-creep hole pulse is transmitted as the finish pulse and opens clutch 29 and the percentage error is read off as fast or slow on the illuminated one of dials 31, 32. The intermediate anti-creep hole pulses are blocked in the counter or divider 49. The standard S may be common to twenty test positions so that Fig. 1 equipment beyond amplifier 19 is repeated at each test position and twenty meters are tested at one time. Circuit operation for full load testing.-In Fig. 4 a selected gang-control unit in the load selector panel 122 operates relays P, Hand Q to prepare input to gas tetrode V2 and include all the scale-of-two stages in Fig. 5 as required for division of photo-cell pulses by 8 corresponding to 4 revolutions of test meter T and actuate that clutch 26 (the clutch windings are shown at 116-121) which couples appropriate shaft 24 to common counter drive 27. The operator also presses button 115 to zeroize dials 31, 32 and operates relay F to extinguish cold cathode tubes V7, V8 and invert the stages in Fig. 5. The start pulse from test meter T- photo-cell 108 in Fig. 4-is amplified at V1 and operates relay G and when G falls back C1 charges and flashes V2 so that capacitor G2 charges and discharges and capacitor C3 delivers a negative pulse to trigger the divider shown at block 107 in Fig. 4 and in detail in Fig. 5. When V5 in Fig. 5 inverts the cathode output at 134 from resistor R47 of push-pull cathode follower V6 fires V7 and Carpenter-type relays E and D operate; E fires gas tetrode V9, whereupon capacitor C23 discharges and excites the engage winding 111 of high-speed clutch 29, Fig. 1, so as to start the counters 31, 32; D lifts the trigger potential of V8 so that a pulse from capacitor C16 will fire V8. E also switches the output from bridge rectifier K2 to sustain the excitation of clutch winding 111. When the ninth pulse from test meter T enters the divider in Fig. 5 the cathode output of V6 again from resistor R47 goes from 135 via C16 to augment the existing trigger voltage on V8 and V8 fires and relays D and E respond to fire gas tetrode V10, whereupon clutch disengage winding 112 is excited and the counters 31, 32 immediately stop and indicate the speed of test meter T. Circuit operation for tests at other loads.-The appropriate gang-control unit in the load selector panel 122 is operated and this actuates the correct clutch relay 26 and H, I or J in the H-Z chain to produce the required speed for counter-shaft 27 and the appropriate pulse division, i.e. 8, 4 or 2. The Specification includes tables setting forth relay &c. details to obtain a nominal count of 100 in the dials for each load in unity and-0.5 power factor test programmes. Testing by reflected light method.-This is an alternative to the transmitted light arrangements of Fig. 1 and operates with photo-cell 109 instead of 108 and relay P de-energized so that the input p<SP>1</SP> to V2 is as shown in Fig. 4 and lamp L6 is used instead of L5. The grid of triode V1 is energized by photo-cell 109 unless the latter is masked by the image of a mark on the test meter disc. Thus G is normally operated and when the reflected image is masked G falls back and V2 fires. If it is necessary to test with a single mark and single revolution of the test meter relays J and N are selected by a gangcontrol unit in panel 122 and the first pulse inverts V5 and the circuit behaviour is then as described above for the full load test; the second pulse inverts V5 so that the right-hand cathode follower of V6 applies a positive voltage to the V8 trigger via C16 and V8 fires to disengage clutch 29. The test meter disc has then completed one revolution. Counter details.-In Fig. 1, two series contacts 37, one fitted to the 1 per cent dial and the other to the 10 per cent dial and worked by cams, are embodied in one of the counting trains and made to close for the large dial from zero to 0.5 and for the small dial from 0.5 through zero to 9.5. In Fig. 4 contacts 150 correspond to 37 in Fig. 1 and when the pointers are in motion the cam-operated contacts 150 break the supply to relay A before the pointers reach the 100 mark whereupon relay B operates and locks and the fast lamps L3, L4 are switched on. When the dials have just passed the 100 per cent mark (if this happens) A becomes re-energized by the cam-operated contacts 150 and relay C operates and locks A to light the slow lamps L1, L2 and extinguish the fast lamps. The pointers are each driven from their shafts through a light friction clutch and when push 115 is operated solenoid-cam control nullifies the friction clutch and returns the pointers to zero.