GB2174555A - Electrical mains adaptor plug - Google Patents

Abstract

An electrical mains adaptor plug (10) incorporates a mains electricity consumption or quantity meter (20) in which the product of current and voltage is derived electrically without moving parts, preferably using a Hall effect device or by pulses representative of both voltage and current. A switch (22) may change the parameter indicated by the meter (20). <IMAGE>

Description

SPECIFICATION Electrical mains adaptor plug This invention relates to an electrical mains adaptor plug.

Frequently it is desired to know the amount of mains electricity consumed by an appliance during a specific time. Where the current consumed by an appliance is known, a measure of the total time during which current flows may suffice, especially if the appliance operates intermittently, such as when thermostatically controlled. Where the current is not constant throughout the "switched on" period, the product of value of current and time during which it flows is a useful measure of the electricity quantity. A further refinement takes account of the variation of voltage during the specified time. It is an object of this invention to satisfy these requirements.

According to the invention, an electrical mains adaptor plug includes on one side a first set of electrical junction elements shaped and positioned to make electrical connection with a standard electrical mains outlet, and includes on another side a second set of electrical junction elements shaped and positioned to act as a standard electrical mains outlet, whereby the adaptor plug may be plugged into a standard mains outlet and an electrical plug which would fit said outlet can be plugged into the adaptor plug, electrical connections between each one of said first set and the corresponding one of said second set of electrical junction elements, the adaptor plug further including meter means to indicate a parameter of any electric current which passes through the adaptor plug.

Conveniently, the meter means is connected internally of the adaptor plug to measure the product of current passing through the adaptor plug and time for which it passes.

Preferably, the meter means measures the product of current and voltage across the junctions in one or other of said sets and time.

The adaptor plug may include a Hall effect multiplier connected to produce an electrical signal indicative of the product of voltage and current.

The adaptor plug may further include a source of electrical pulses of which the frequency is proportional to said parameter, and a counter to count the pulses throughout the time for which electrical current passes through the adaptor plug.

According to another aspect of the invention, there is provided a method of measuring the quantity of electricity consumed by an appliance in a given time, including generating a direct current voltage proportional to one or more parameters of the electricity, generating a stream of electrical pulses at a frequency proportional to said direct current voltage and counting the number of said pulses throughout said given time.

The invention is described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of one form of adaptor plug according to the invention.

Figure 2 is an electrical circuit diagram of one embodiment of the invention, and Figure 3 is an electrical circuit diagram of another embodiment of the invention.

In Figure 1 a plastic parallelopiped body 10 has one face in which are formed three sockets 12, 13, 14 shaped and positioned to receive the three flat pins of a standard 13 amp single phase alternating current mains plug.

Protruding from an opposite face 15 of the body 10 are three pins 16, 17, 18 positioned and located as the pins of a standard 13 amp mains plug. The socket 12 is connected internally of the body 10 to the pin 16 as the earth connection. The socket 13 is connected internally to the pin 17 as the neutral connection. The socket 14 is connected internally to the pin 18 as the live connection.

A digital meter 20 forming the display of an electrical pulse counter is resettable to zero by a button 21. A multi-position switch 22 is switchable between a plurality of positions in each of which the meter 20 indicates a different parameter.

In Figure 2 the pin 16, 17, 18 are connected to the sockets 12, 13, 14 respectively by wires 24, 25, 26. The wire 26 is wound as a low resistance current winding 27 around which is would a coil 28 magnetically coupled to the winding 27, so that the voltage induced in the coil 28 is proportional to the current through the winding 27. A laminated iron or ferrite core may be provided to couple the winding 27 and coils 28.

The coil 28 is connected to a conventional fullwave rectifier 29 of four diodes. The rectifier 29 outlet is a direct current voltage proportional to the current through the winding 27, and connected, as shown, to a voltage-to-frequency oscillator 30 of known kind which emits a stream of electrical pulses of which the frequency is proportional to the direct current voltage applied thereto. The pulses from the oscillator 30 are fed to a pulse counter 31 which registers the number of pulses counted on the meter 20 or a submultiple thereof.

To use the adaptor plug, the pins 16, 17, 18 are plugged into a standard single phase 13 amp mains outlet socket, and a standard 13 amp mains plug is plugged into the sockets 12, 13, 14, the standard plug being electrically wired to the appliance of which the electrical parameter is to be measured.

As soon as current starts to pass through the adaptor plug, via the winding 27, a stream of pulses will be emitted by the oscillator 30, counted on the counter 31 and displayed on the meter 20. If the current is steady, the count on the meter 20 will be proportional to the steady current and to the time it flows. Thus, it will indicate the quantity of electricity used by the appliance, in Coulombs ampere-hours or the like. The value can be deduced by taking the difference between starting and stopping readings on the meter 20. More conveniently, the button 21 is used to reset the meter 20 to zero before the current starts to flow.

It will also be seen that if the value of the current through the winding 27 varies with time, the frequency of pulses emitted by the oscillator 30 will vary proportionally, so that the meter 20 will still measure the true quantity of electricity passing to the appliance.

In some cases the appliance may take a constant current between any switched interuptions, for example, if it is thermostatically controlled. In this case a measure of the total time during which the current actually flows may be an adequate parameter to measure. For such purposes the oscillator 30 need not be so sophisticated as a voltage-to-frequency type but a fixed frequency oscillator will suffice, to oscillate whenever a voltage from the rectifier 29 is applied thereto.

As a further refinement the switch 22 may be used to change the oscillator 30 from a fixed frequency mode to a voltage-to-frequency mode, as required.

Figure 3 shows a further refinement of the circuit shown in Figure 2, in which the instantaneous voltage is multiplied by the instantaneous current to give a parameter of instantaneous watts. For this purpose a voltage signal is taken by a high resistance Potentiometer 35 connected across the line and neutral sockets 14, 13. The output of the potentionmeter 35 connects through a double pole switch 36 to opposite ends of a Hall effect device 37 of known kind. The opposite sides of the Hall effect device 37 are connected to the imputs of the rectifier 29, which feeds the voltage-to-frequency oscillator 30 and counter 31, as in Figure 2.

The current winding 27 in Figure 3 is positioned so that its central magnetic field passes through the Hall effect device 37 and is normal to the line joining the opposite ends thereof and also normal to the line joining the opposite sides thereof. When a voltage is applied to the opposite ends and the magnetic field is present in the winding 27, a voltage is generated across the opposite sides and thus fed to the rectifier 29. The magnitude of the voltage thus generated is proportional to the applied voltage and to the current in the winding 27.

The voltage applied to the rectifier 29 and the direct current voltage fed to the oscillator 30 are therefore proportional to the product of voltage and current. The counter 31 will consequently be proportional to the watts passing through the adaptor plug.

Over the time of usage of the appliance the counter will idicate a measure of the watt hours of electricity used, even though the mains voltage and/or current to the appliance may change during that time.

By changing over the switch 36 a voltage proportional to the mains voltage is fed to the counter 31 so that the latter can optionally measure the actual time for which the mains voltage is fed to the appliance, which is a useful parameter for certain purposes.

Instead of the embodiments described above, other circuits or apparatus may be incorporated into the adaptor plug, for the purpose of measuring one or more of the aforesaid parameters. For example, the amount of electricity used may be recorded by a small version of a conventional watt hour meter built into the adaptor plug, such as a rotating disc eddy current device.

The circuits in Figures 2 and 3 are diagramatic only, the voltage-to-frequency oscillator 30 counter 31 and Hall effect device 37 are well-known devices in themselves and the values of the components will be apparent to those skilled in the art of electronics.

Claims (9)

1. An electrical mains adaptor plug including on one side a first set of electrical junction elements shaped and positioned to make electrical connection with a standard electrical mains outlet, and including on another side a second set of electrical junction elements shaped and positioned to act as a standard electrical mains outlet, whereby the adaptor plug may be plugged into a standard mains outlet and an electrical plug which would fit said outlet can be plugged into the adaptor plug, electrical connections between each one of said first set and the corresponding one of said second set of electrical junction elements, the adaptor plug further including meter means to indicate a parameter of any electric current which passes through the adaptor plug.

2. An adaptor plug, according to Claim 1, in which the meter means is connected internally of the adaptor plug to measure the product of current passing through the adaptor plug and time for which it passes.

3. An adaptor plug, according to Claim 2, in which the meter means measures the product of current and voltage across the junctions in one or other of said sets and time.

4. An adaptor plug, according to Claim 3, including a Hall effect multiplier connected to produce an electrical signal indicative of the product of voltage and current.

5. An adaptor plug, according to any preceding claim including a source of electrical pulses of which the frequency is proportional to said parameter, and a counter to count the pulses throughout the time for which electrical current passes through the adaptor plug.

6. An adaptor plug, according to Claim 1, in which the meter means indicates the length of time for which a voltage is applied to one of the sets of junction elements.

7. An adaptor plug, according to Claims 4 or 5, in which the counter is resettable to zero at the start of a measurement.

8. An electrical mains adaptor plug, constructed and arranged and adapted to operate substantially as described herein and as shown in the accompanying drawings.

9. A method of measuring the quantity of electricity consumed by an appliance in a given time, including generating a direct current voltage proportional to one or more parameters of the elec tricity, generating a stream of electrical pulses at a frequency proportional to said direct current voltage and counting the number of said pulses throughout said given time.