GB2096773A

GB2096773A - Measuring and display apparatus

Info

Publication number: GB2096773A
Application number: GB8209657A
Authority: GB
Original assignee: LEO ELECTRONICS S Pte Ltd
Current assignee: LEO ELECTRONICS S Pte Ltd
Priority date: 1981-04-11
Filing date: 1982-04-01
Publication date: 1982-10-20

Abstract

The apparatus is for measuring and selectively displaying a plurality of quantities relating to the operation of a motor vehicle, for example the road speed, engine speed, engine cooling water temperature, and battery voltage. The apparatus comprises a display 21 e.g. an alpha-numeric display 4, a plurality of sensing devices 22, 23, 24, 25 and a selector 8 which, through a microelectronic control circuit 20, permits selection of any of the measured quantities for display. Audible warnings can be given at pre-determined values of any of the quantities, for example to warn of excessive road or engine speed, or water temperature, or low battery voltage. Different pre-determined speeds at which a warning is given may be selected by rotary switch 6. <IMAGE>

Description

SPECIFICATION Measuring and display apparatus This invention relates to an apparatus for measuring and selectively displaying a plurality of quantities relating to the operation of a motor vehicle, for example the road speed, engine speed, engine cooling water temperature and battery voltage.

According to the invention, the apparatus comprises a display means, a plurality of measuring devices each arranged to generate a signal corresponding to one of the quantities to be measured, and selector means for selectively connecting the detector means to the display means, whereby the selected quantity measured may be displayed.

Preferably the display means is in the form of an alpha-numeric display upon which the measured quantity can be displayed numerically.

The display is conveniently formed from lightemitting diode segments, since the display can then be seen clearly in darkness. Alternatively, a vacuum fluorescent type of display can be used.

The apparatus may also include audible warning means, for example, a buzzer, arranged to operate when a pre-set level of any measured quantity is reached or exceeded, or, in the case of battery voltage, when the measured quantity falls below the pre-set level. The display may also be arranged to operate intermittently, for example to switch on and off at a frequency of 2 Hz when the audible warning means is operating. A timing circuit may cancel the audible warning, and the intermittent operation of the display, after a predetermined period, for example 10 seconds, to avoid causing irritation to the driver of the motor vehicle.

An advantage of the apparatus is that it can be installed in any motor vehicle as an accessory and can thus be used to supplement existing instruments as well as providing the functions of additional instruments.

Reference is made to the drawings, in which: Figure 1 is a front elevation of an apparatus in accordance with a preferred embodiment of the invention; and Figure 2 is a block circuit diagram of the apparatus of Figure 1.

Referring first to Figure 1, the apparatus has a control and display unit 1 pivotally mounted in a bracket 2 by which it may be secured to a suitable surface within the motor vehicle. The control and display unit 1 contains electronic circuitry, described hereinafter in more detail with reference to Figure 2, and has visible on the front face 3 thereof a display 4 formed of a plurality of light-emitting segments 5. A rotary switch 6 is rotatable to permit selection of any of three different pre-determined speeds at which a warning is to be given, and a calibration screw 7 enables the device to be calibrated against the vehicle's conventional mechanical speedometer.

At the rear face of the unit 1 (not shown) a three-position selector switch enables the device to be set for four, six or eight cylinder engines, for the tachometer mode.

The different modes of operation of the apparatus are selected sequentially by repeated operation of the mode selector switch 8, which is a touch-sensitive type of switch. Each touch on the switch 8 causes the next mode in the sequence to be selected. The modes of operation provided are described hereinafter with reference to Figure 2. A reset switch 9 is also provided on the device, adjacent to the calibration screw. This serves to reset the control circuit after the overspeed limit has been selected or changed during driving, and to stop any audible warning signal temporarily, e.g. for a period of approximately one minute.

In the block circuit diagram of Figure 2, the central component is an integrated microelectronic control circuit 20 which principally controls the conversion of the signals provided by the measuring devices into a form which can control operation of a display 21 to provide a numerical display of the quantity measured. The measuring devices comprise a connection 22 to the distributor of the vehicle engine, or to the low tension side of the ignition coil, to provide a series of electrical pulses proportional to engine speed, a speed sensor 23 attached to the vehicle speedometer or inserted in the cable drive thereto, a temperature sensor 24 inserted into a cooling water passageway in the vehicle engine block and a connection 25 to the vehicle battery.

Each measuring device has a respective associated conversion circuit 26, 27, 28 or 29 connected in turn to the control circuit 20 and providing a measurement signal in suitable form.

Further connections are made between the vehilce ignition key switch 30 and the battery conversion circuit 29, and between the vehicle lighting control switch 31 and a detector circuit 32 in turn connected to the control circuit 20. A buzzer 33 is also operated by the control circuit 20.

Operating features for a preferred embodiment of the apparatus, for each mode thereof, are as follows: Tachometer mode Range of Engine Speeds: 500 to 9999 revolutions per minute (rpm) Excess Speed Warning operates above 6500 rpm, giving a 2 HZ intermittent buzzer signal, the buzzer operating at 4.6 kHz.

Speedometer mode Range of Vehicle Speeds: 8 to 250 km/h 5 to 150 miles/hour

alternative seiectable scales The alternative scales are selected by a switch 34 (Figure 2).

Calibration: Turning calibration screw 7 rotates a potentiometer, the reading being adjusted to agree with the vehicle's mechanical speedometer reading at a steady speed of 30 miles per hour or 50 kilometers per hour.

The warning signal operates when any selected one of three set speeds is exceeded, the warning taking the form of two pulses at the rate of 4Hz repeated at 0.5 second intervals, again operating the 4.6 kHz buzzer.

Voltmeter Range: 8 to 18 volts DC Warning buzzer operates below 11 volts with a pulsed 1 Hz signal at 4.6 kHz.

Temperature gauge Range: 400C to +1 500C.

Warning buzzer operates at temperatures below OOC and above 1 00C with a steady signal for 10 seconds.

Headlight reminder The connections to the vehicle light switch and to the ignition switch enable the apparatus to give a signal if the ignition is switched off, but the headlights remain switched on. A ten second signal pulsed at 1 Hz is given.

It will be noted that the warning signals operate regardless of the mode selected, or even if no measurements are being displayed.

Claims

1. Apparatus for measuring and selectively displaying a plurality of quantities relating to the operation of a motor vehicle, comprising a display means, a plurality of measuring devices each arranged to generate a signal corresponding to one of the quantities to be measured, and selector means for selectively connecting the detector means to the display means, whereby the selected quantity may be displayed.

2. An apparatus according to Claim 1, wherein the display means comprises an alpha-numeric display.

3. An apparatus according to Claim 1 or 2, comprising audible warning means arranged to operated when a pre-set level of any measured quantity is reached or exceeded, or when the quantity falls below the pre-set level, according to the nature of the measured quantity.

4. An apparatus according to Claim 3, wherein the display means is arranged to operate intermittently when the audible warning means is operating.

5. An apparatus according to Claim 4, wherein the display switches on and off at a frequency of approximately 2 Hz when the audible warning means is operating.

6. An apparatus for measuring and selectively displaying a plurality of quantities relating to the operation of a motor vehicle, substantially as described herein with reference to, or as shown in, the drawings.