SE333773B - - Google Patents

Abstract

1,116,680. Selective signalling. SIEMENS A.G. 1 May, 1967 [29 April, 1966], No. 20081/67. Heading G4H. [Also in Division G1] The rotor of an electricity meter coupled to an installation which may experience either an inflow or an outflow of power would normally reverse direction when the condition changes from inflow to outflow or vice versa. The invention provides (see Division G1) a metering system for such an installation in which, when such a reversal occurs, the connections to the current or voltage drive magnet are automatically reversed to restore forward running, but the indicator previously in use is switched out and a separate indicator is switched in. Fig. 2 shows the system for detecting the initial reversal and for operating switches which restore the forward running of the rotor and the change of indicator. The rotor rotation is sensed by a pair of Hall Effect devices arranged to provide signals which are 90 degrees apart. The two sets of signals are fed to respective bistable stages 14 and 15 which in turn feed square output pulses both directly and by way of respective inverter stages 16 and 17 to a stage 18 which differentiates the inputs. The stage 18 thus receives quadrature spaced inputs, each of which are differentiated. The pattern of coincidences between a given non-differentiated signal and the differential of another signal is dependent on the sense of rotation of the rotor, and this property is exploited to operate an output A0 for one sense of rotation and an output A1 for the other. On reversal, relay 9 is operated to restore forward running, but the connection to relay 9 is via a stage 19 which has a memory function to ensure that the restoration of forward running by the relay 9 is not detected by the system as a re-reversal requiring a second change of indicator. The indicators, which may be remote, are driven by pulses derived from the quadrature spaced pulses fed to stage 18 but passed through stages 21 to 26 where the pulses are shaped to a predetermined amplitude and duration. It is arranged that, in response to a reversal detected at 18, the final output pulse train is positive or negative going in dependence on whether an inflow or an outflow condition exists. Alternatively, both inflow and outflow conditions may produce pulses of the same polarity but different D.C. level.