| 摘要 |
1288609 Electric selective signalling SPERRY RAND CORP 29 Dec 1969 [14 Jan 1969] 63039/69 Heading G4H Apparatus for producing an analogue output signal V 0 proportional to the angular difference between an electrical analogue input signal representing a first angle # and an electrical digital input signal representing a second angle # comprises a controller 30 for receiving the digital input signal and sine and cosine functions of the analogue input signal, a digital to analogue converter 36-39, 41-44 for converting the digital signal to first and second pairs of sine and cosine functions of a first value #a and a second value #b of the digital signal (where #a<#<#b) and transformers 51, 56 for providing a first difference signal which is a function of (#a-#) and a second difference signal which is a function of (#b-#). As described the apparatus is used with a flux valve 11 from which the analogue input signal is derived to determine direction with respect to the horizontal component of the earth's magnetic field, # being the angle between this component and the axis of the valve. The flux valve consists of a primary coil 12 energized by a source of frequency # and secondary coils 14-16 which are connected to the primaries 23, 24 of a transformer 25. The two outputs of the transformer are fed to the controller shown in Fig. 2 which comprises the four transformers 36-39. The controller 30 generates the signal V 0 , the polarity of which is determined by a phase detector 32 fed with a reference signal. The output of the phase detector is fed to an up/down counter 33 in which logic circuits are gated by pulses from a master clock, the count stopping when the digital signal # equals # since V 0 then equals zero. The digital signal # may be processed in a digital computer or displayed to a pilot to control the heading of a craft in which the apparatus is installed. The two most significant bits of # determine the quadrant in which # lies whilst the next three significant bits select the taps of the transformers 36-39 to determine # within a range of eleven degrees and generate a coarse signal V sin (#a-#) sin wt. The coarse signal is combined with a fine signal derived from a resistive ladder digital to analogue converter 45 controlled by the ten least significant bits of # to provide an accurate digital representation of #. |
