Means for measuring speed or distance

Claim 3

An apparatus according to claim 1, wherein the semiconductor device comprises a photo-transistor the base electrode of which is left unconnected, and the solid stage infra-red source comprises a gallium arsenide lamp.

Claim 4

An apparatus according to claim 2, further comprising a zener diode connected in parallel with the gallium arsenide lamp and the photo-transistor for stabilizing the voltage across said lamp and said photo-transistor, and a diode connected across the emitter-collector electrodes of the photo-transistor for ensuring clean switching thereof and for preventing reverse transients from causing multiple switchiNg of the photo-transistor.

Claim 5

An apparatus according to claim 1, wherein said semiconductor device comprises a photo-transistor and transistor arranged as a darlington pair with commoned collector electrodes and the emitter electrode of the photo-transistor connected to the base electrode of the transistor, and wherein a pair of series diodes is connected between the commoned collector electrodes and the base electrode of the first transistor of the amplifier.

Claim 6

An apparatus according to claim 1, wherein the opaque element is a disc having a cut out portion which extends through 180*, whereby the square wave voltage generated by the semiconductor device has a mark-space ratio which equals unity.

Claim 7

An apparatus according to claim 1, wherein the last stage of said amplifier comprises a transistor which switches ''''on'''' during the ''''off'''' period in which the infra-red radiation is cut off from the semiconductor device and which switches ''''off'''' during the ''''on'''' period in which infra-red radiation reaches the semiconductor device, the means for integrating the output of the amplifier includes an ammeter, a capacitor and a diode, the diode and ammeter being connected in parallel with one another, and the capacitor being connected between the output of the last stage of the amplifier and the parallel combination of diode and ammeter so that the emitter-collector circuit of the transistor forming the last stage of the amplifier short circuits the capacitor and meter when said last stage transistor switches ''''on,'''' said capacitor being charged by the current which passes through the ammeter when the transistor forming the last stage of the amplifier switches ''''off.''''

Claim 8

An apparatus according to claim 2, wherein said opaque element comprises a rotor having a cylindrical cup at one end with a single aperture therein, said gallium arsenide lamp extending into said cup and being fixed to a stator and said photo-transistor being housed in the wall of the stator in line with the rotating aperture in the cylindrical cup and said gallium arsenide lamp.

Claim 9

In combination, a road vehicle and an apparatus for determining the engine revolutions of the road vehicle including a semiconductor device sensitive to infrared radiation for generating a square wave voltage pulse by switching on when exposed to the infra-red radiation and switching off when the infra-red radiation is cut off therefrom; a solid state infra-red radiation source; an element opaque to infra-red radiation having a single aperture formed therein, said opaque element being positioned between said source and said semiconductor device; means for moving the opaque element in timed relation to the engine revolutions of said road vehicle; a transistorized amplifier having a plurality of inversely switching transistor stages, means for connecting said transistorized amplifier to the semiconductor device such that the semiconductor device and the transistor stages of the amplifier switch inversely in cascade between an ''''on'''' state and an ''''off'''' state so that a transistor of one stage is always conducting so as to produce a square wave voltage pulse every time a pulse occurs from the output of the semiconductor device; and electrical storage means charged from a source responsive to the switching off of the last stage of said amplifier; and means for measuring the average value of inrush charging currents to said electrical storage means so as to produce a direct reading of the engine revolutions of the vehicle.

Claim 10

In combination, a road vehicle and an apparatus for determining the engine revolutions of the road vehicle including a semiconductor device sensitive to infrared radiation for generating a square wave voltage pulse by switching on when exposed to the infra-red radiation and switching off when the infra-red radiation is cut off therefrom; a solid state infra-red radiation source; an element opaque to infra-red radiation having a single aperture formed therein, said opaque element being positioned between said source and said semiconductor device; means for moving the opaque element in timed relation to the engine revolutions of said road vehicle; a transistorized amplifier having a plurality of inversely switching transistor stages, means for connecting said transistorized amplifier to the semiconductor device such that the semiconductor device and the transistor stages of the amplifier switch inversely in cascade between an ''''on'''' state and an ''''off'''' state so that a transistor of one stage is always conducting so as to produce a square wave voltage pulse every time a pulse occurs from the output of the semiconductor device; and electrical storage means charged from a source responsive to the switching off of the last stage of said amplifier; and means for measuring the average value of inrush charging currents to said electrical storage means so as to produce a direct reading of the engine revolutions of the vehicle.

Claim 11

The combination according to claim 8, wherein the means for effecting a summation of the pulses from the output of the amplifier includes an ammeter, a capacitor, a diode, a zener diode and a transistor, means for connecting said capacitor in series with said amplifier across the collector-emitter path of the transistor, means for connecting said diode across said ammeter and zener diode across the collector-emitter path of the transistor so that the transistor causes short circuiting of the capacitor when said transistor is turned ''''on'''' during the ''''off'''' period in which the infra-red radiation is cut off from the semiconductor device, said capacitor being charged by the current which passes through the meter when the transistor switches ''''off'''' during the ''''on''''period in which the infra-red radiation reaches the semiconductor device.

Claim 12

The combination according to claim 8, wherein said opaque member comprises a rotor having a cylindrical cup at one end with an aperture in the wall thereof, said solid state source being fixed to a stator and being housed within said cup, and the semiconductor device being housed in the wall of the stator in line with the solid state source and in the same plane as the aperture in the wall of the cup.

Claim 13

The combination according to claim 8, wherein the semiconductor device comprises a photo-darlington pair and the infra-red radiation source comprises a gallium arsenide lamp, said combination further comprising a zener diode connected in parallel with a first series arm comprising the gallium arsenide lamp and a resistor, and a second series arm comprising a photo-darlington pair and a resistor, the three armed parallel circuit so formed being connected in series with a resistor across a D.C. voltage source.

Claim 16

A device according to claim 12, wherein the solid state radiation source comprises a gallium arsenide infra-red lamp.

Claim 17

A device according to claim 12, wherein the cut away portion of the disc extends through 180* of the circumference of the disc.