GB2034085A - Measuring instrument - Google Patents

Abstract

A measuring instrument suitable for measuring the distance travelled or area covered by agricultural vehicles utilises a pocket calculator of the kind having an automatic constant facility on the plus function. A magnetic switch 12 operated by wheel rotation is connected through pulse lengthening means to the plus function so that by keying in the wheel circumference or unit area covered the calculator accumulates a read out of distance or total area covered. <IMAGE>

Description

SPECIFICATION Measuring instrument This invention relates to a measuring instrument and in particular, but not exclusively, to a measuring instrument for use in agriculture for measuring the area or distance covered by agricultural vehicles.

It often arises in agricultural work that it is required to know the distance travelled by a tractor or other vehicle in precise terms. Moreover, for example when applying a liquid spray, it is necessary to know the area covered by the spray to determine the application rate per unit area.

Prior measuring instruments for this purpose have been bulky and expensive and have comprised a device for counting the revolutions of a vehicle wheel and specially designed electrically-operated equipment for computing and displaying the information required using data fed in by the operator and the counting device.

An object of the present invention is to provide a measuring device in which mass-produced and, therefore, cheap components can be utilised.

According to the invention a measuring instrument comprises a device for counting the revolutions of a rotating element, an electrically operated pocket calculator of the kind having an automatic constant facility on the plus function, a multiplication function and a division function, the counting device being arranged to transmit an electrical signal in the form of an electrical pulse for each revolution of the rotating element to the calculator so that the signal can operate the calculator, and pulse lengthening means in the electrical circuit from the counting device to the calculator to ensure that the calculator is activated once for each revolution of the element.

In utilising a pocket calculator as a measuring device on agricultural tractors it has been found to be unsatisfactory to feed signals from a counting device direct to the calculator because at the usual forward speeds involved the signals are of very short duration and do not always register accurately. Moreover, erroneous transient signals may be produced. The use of the pulse lengthening means obviates these problems.

It is desirable to operate the device from the electrical system of the vehicle on which it is mounted but it has been found that the electrical supply is subject to fluctuations and changes. To overcome this problem it is preferred to incorporate in the electrical supply to the calculator a voltage regulator and transient voltage suppressor.

Further features of the invention appear from the following description of an embodiment of the invention given by way of example only and with reference to the drawings, in which: Fig. 1 is a circuit diagram showing the measuring instrument in use for measuring various parameters required by tractor operators.

Fig. 2 is a circuit diagram of one part of the circuit of Fig. 1, and Fig. 3 is a circuit diagram of another part of the circuit of Fig. 1.

Referring to the drawings a measuring instrument is fitted to an agricultural tractor of the kind having an undriven wheel 10. A permanent magnet 11 is mounted on the wheel 10 spaced from the axis of rotation thereof so as to make one revolution for each revolution of the wheel. An electrical switch 12 is located adjacent the path of the magnet to be operated by the magnet once each revolution of the wheel 1 0. Instead of the switch 1 2 being magnetically operated the switch may be mechanically operated and, in either case, operation of the switch causes an electrical pulse to pass from the switch to a pulse stretching or lengthening means 13 to be described.

The lengthened pulse is transmitted to a calculator 14 of known form, usually termed a pocket calculator, and of the kind having an automatic constant facility on the plus function in addition to the usual division and multiplication functions. The calculator also has the usual visual display and push button data feeding arrangement. The supply from the means 1 3 is connected to the automatic constant facility on the calculator, as will become apparent when describing the operation of the instrument.

Power supply to the calculator is from the usual tractor electrical system 1 5 through a voltage regulator and transient voltage surge suppressor means 17, to be described, and to the calculator connections which are usually connected to a storage battery.

Since, in this embodiment, the battery is omitted the means 13 and 17 can, in practice, be housed in the calculator compartment normally provided for the battery.

The calculator 14 portion of the instrument is mounted on the tractor in a position in which it can be readily observed and operated by the driver.

Referring now to Fig. 2, this shows the circuitry of the pulse lengthening means 13 which includes connections 1 8 to the automatic constant facility key or button on the calculator and a connection 1 9 to the positive supply on the calculator. The circuit includes a switch 20, a capacitor 21, a resistor 22 and a transistor 23.

In Fig. 3 there is shown a circuit incorporated in the voltage regulator and transient voltage surge suppressor means 1 7. The circuit is interposed between the electrical supply 1 5 and the connections 24 to the calculator 14 and includes an on-off switch 25 in series with a diode 26 and a resistor 27. Two capacitors 28 and 29, a voltage regulator 30 and a resistor 31 are also in the circuit.

Operation of the instrument is as follows: It is first necessary to determine the circumference of the wheel to which the magnet 11 is fitted and in order to measure the distance covered by the vehicle this circumference is fed into the calculator by depressing the appropriate buttons and the constant facility key is also depressed. As the vehicle moves each rotation of the wheel causes the wheel circumference to be added to a running total thereby giving a read out of total distance travelled.

To measure area covered by, for example, a spraying boom having a certain width of coverage, the calculator is initially programmed by multiplying the wheel circumference by the width of the boom. The constant facility key on the calculator is again depressed so that the calculator registers area covered. It will be appreciated that the application rate of the spray per unit area can be readily ascertained knowing the area covered and the amount of material sprayed, again by using the calculator.

It will be appreciated that the instrument has many uses in the field of agriculture and could also find application elsewhere when accurate distances and areas need to be known.

In adopting existing instrumentation the invention has achieved great savings in cost without loss of accuracy and, if desired, the calculator portion of the instrument can still be used for its original function.

Claims (8)

1. A measuring instrument comprising a counting device activated by the revolutions of a rotating element, an electrically-operated 'pocket' calculator of the kind having an automatic constant facility on the plus function, a multiplication function and a division function, the counting device being arranged to transmit an electrical signal in fhe form of an electrical pulse for each revolution of the rotating element to the calculator, and pulse lengthening means in the electrical circuit from the counting device to the calculator to ensure that the calculator is activated upon each revolution of the element.

2. An instrument according to claim 1 wherein the calculator is mounted on an agricultural vehicle, the counting device is arranged to count the revolutions of an undriven wheel of the vehicle and the instrument is supplied with power from the vehicle electrical system.

3. An instrument according to claim 2 wherein the electrical power supply to the calculator includes a voltage regulator and a transient voltage suppressor.

4. An instrument according to any one of the preceding claims wherein the output signal from the counting device is fed to the automatic constant facility on the plus function.

5. A method of operating a measuring instrument wherein an electrically operated 'pocket' calculator having an automatic constant facility on the plus function, a multiplication function and a division function is connected to a counting device for counting the revolutions of a rotating element so that an electrical signal is transmitted from the counting device to the calculator through a pulse lengthening means and the plus facility is activated upon each revolution of the rotating element.

6. A method according to claim 5 wherein the calculator is connected to the electrical supply of an agricultural tractor through a voltage regulator and a transient voltage suppressor.

7. A method according to claim 5 or 6 wherein the circumference of an undriven wheel to which the counting device is attached is keyed into the calculator in measuring distance travelled.

8. A measuring instrument substantially as described with reference to the drawings.