Patent GB-361284-A (GB)
Title: Improvements in or relating to distance or depth finding apparatus
IPC: G01S15/10
Filed: 1930-07-11
Abstract: 361,284. Determining distances acoustically. SUBMARINE SIGNAL CO., 160, State Street, Boston, Massachusetts, U.S.A.-(Assignees of Turner, E. E. ; 130, Willow Street, West Roxbury, Massachusetts, U.S.A.) July 11, 1930, No. 21069. Convention date, July 29, 1929. [Class 118 (ii).] In a device for measuring distances, depth of water, or height in air by measuring the time interval between the sending of a signal and the return of its echo, the time measuring means comprises a thermionic valve circuit having a floating grid, and a condenser discharging at a known rate which is connected at the end of the time interval to the grid and the resulting potential measured by measuring the anode current. The sound is emitted by a hammer 7 on a bell-crank lever 5, which strikes a diaphragm 1 each time the arm 28 is lifted and released by a motor-driven disc 3 with pin 4. The sound is reflected by the surface 29 and received and amplified by a device 22, 23 preferably of the type described in Specification 309,901, [Class 118 (ii), Signals]. The contact 9, 10 is broken when the hammer 7 strikes the diaphragm 1, and the condenser 13, which was charged to the potential of the battery 12, commences to leak through the resistance 14 at a known rate. The operation of the relay 24 of the receiving circuit completes the contact 26, 27, places the condenser 15 and the grid of the valve 16 at the same potential as the condenser 13. and immediately breaks the contact 26, 27 to isolate the condenser 15. The potential of the grid of the valve 16 is thus a function of the time interval during which the condenser 13 is discharging, i.e. the time taken by the passage of the sound signal, and may be measured by measuring the anode current passing through an ammeter 17 or recording ammeter 18. If desired, a relay 19 operating at a definite current value may operate an alarm 20. The reading on the ammeter 17 remains constant with succeeding signals unless the depth changes. In Fig. 2 the time element of the relay 24 is eliminated and the time measurement is effected when contacts 26, 30 are opened and not when contacts 26, 27 are closed. The sensitivity of the circuit also increases with the length of the time interval, i.e. as the echo becomes weaker with greater depth. The condenser 13 is continually connected to the grid of the valve 31 during its-discharge, and the impulse received by the hydrophone 22 is also impressed on the grid through the transformer 32. The impulse received due to the direct signal is not sufficient to overcome the effect due to the condenser 13 since the charge will not have leaked appreciably, and the grid will remain highly negative even with a powerful direct signal. A subsequent signal when the potential of the condenser 13 is reduced by leakage becomes effective to operate the receiving circuit at the moment the contacts 26, 30 are opened while the subsequent closing of contacts 26, 27 connects the condenser 13 of the grid of the valve 16 which operates the indicator 17. Specification 161,988, [Class 118 (ii), Signals], also is referred to.