Patent GB-1203310-A (GB)
Title: Apparatus for digital computation of intervals of time, particularly for distance measurement on the echo priciple with electromagnetic or acoustic pulses
IPC: G01S13/70
Filed: 1968-10-18
Abstract: 1,203,310. Measuring time intervals. FRIED. KRUPP G.m.b.H. 18 Oct., 1968 [18 Oct., 1967], No. 49484/68. Heading G4H. [Also in Division H4] Apparatus for digitally measuring time intervals by the echo process includes a counter 12 (Fig. 1) receiving counting pulses via a gate 10 from a start pulse St to an end pulse E<SP>1</SP> and a digital store 7 to which the contents of the counter 12 are transferred via gates 13 if the difference between successive measurements does not exceed predetermined limits. In the embodiment of Fig. 1 for measuring for example the depth of the sea, a bi-stable 11 controlling the gate 10 receives the start pulse St and the echo pulse E<SP>1</SP>. A fixed time after the echo pulse has been received a delay 24 enables gate 17 to transfer the contents of binary coded decimal counter 12 to preset counter 16. Counter 12 is then cleared and the second measurement effected, the counting pulses during the second measurement also being applied to an auxiliary counter 21 which after, for example, five pulses allows the remaining pulses to be applied to count down counter 16. If at the end of this measurement cycle the count in counter 16 is less than 10 (that is lead 25 connected to the counter 16 by diodes is at "1") a JK flip-flip 23 is switched by the echo pulse E<SP>1</SP> via delay 24 to energize gates 13 and transfer the count in counter 12 to the output store 7. The counter 16 is then cleared and the new measured value in counter 12 entered in it. An interlock 27 holds line 25 at zero if no echo pulse is received. In one modification (Fig. 3, not shown) the reversible counter 16 is replaced by a second counter (12<SP>1</SP>) the counters (12, 12<SP>1</SP>) being used alternatively and their outputs at the end of each measurement cycle being compared in a difference former (40) to which is connected logic circuitry (22<SP>1</SP>) which transmits a transfer signal to gates (13) if the difference between the two counts is within predetermined limits. In the embodiment of Fig. 4 (not shown), at the end of each measurement cycle the contents of the counter (12) are transferred to a store (41) the contents of the store and counter being compared at the end of each cycle. In the embodiment of Fig. 5 (not shown), the counter (12) has a plurality of stores (41x, 41y, 41z) a difference former (43) measuring the difference between the contents of pairs of stores and if only one of the pairs is within the required limits the associated gate (13x, 13y, 13z) is enabled to transfer the contents of its associated still. Alternatively, the means value may be transmitted. To follow rapid changes in the depth of the water (e.g. determining the position of wrecks) the difference between first and second measurements is first determined to see whether it is less than a predetermined larger tolerance, e.g. 20 and similarly for the second and third measurements. The difference between these two sets of measurements is then found in a further difference former with a lower tolerance range controlling logic (46, Fig. 6, not shown) to enable one of the three measured values to be stored. In the embodiment of Fig. 7 (not shown), a counter (12<SP>1</SP>) counts pulses of a third the frequency for three measurement cycles and the count is compared with the count of a single measurement cycle held in a counter (12) to control the gates (13) to the output store (7). In the embodiment of Fig. 8 (not shown), the contents of a counter (12) are entered into a reversible counter (16) at the end of each third measuring cycle, the reversible counter being counted down for the three cycles by pulses of one-third the frequency and the difference being determined after three cycles to see if it falls within the predetermined limits.