GB897588A - Improvements in or relating to an arrangement for selective voltage output measurement - Google Patents

Abstract

897,588. Testing apparatus. SIEMENS & HALSKE A.G. Aug. 20, 1959 [Aug. 22, 1958], No. 28513/59. Class 37. Testing apparatus comprises a first generator 1, Fig. 1, the frequency of which may be locked to a harmonic of a crystal oscillator 2, a second generator 9 the frequency of which is adjustable by a tunable oscillator 14 over a band, the width of which is equal to the frequency spacing of two adjacent harmonics of oscillator 2, and a measuring receiver, Fig. 2, including a first conversion stage 25 the auxiliary frequency of which is equal to the frequency of generator 1, and a second conversion stage 35 the auxiliary frequency of which is equal to, or derived from that of oscillator 14. Crystal oscillator 12, which determines the basic frequency of generator 9 may be replaced by a filter which selects one harmonic from oscillator 2. Separate generators 26, 36 are preferably not used, but generators 1, 9 supply the auxiliary frequencies for conversion stages 25, 35. The output of stage 35 may be still further reduced in frequency in stage 45 before being supplied to an evaluation device 50 through a wide band pass filter 47 or a narrow band pass filter 46. When a continuously variable test frequency is required, frequency determining element 5, e.g. a reactance valve is replaced for example by a rotary capacitor, and generator 26 is similarly modulated. The output of the measuring receiver is in this case, applied to a cathode-ray tube which also receives a deflection voltage proportional to the instantaneous test frequency. Auxiliary frequency fq supplied to stage 46 may be automatically adjusted Fig. 4 (not shown), to maintain the output of stage 45 at the centre-pass frequency of the selected filter 46 or 47.