GB2125972A

GB2125972A - Domestic electrical tester

Info

Publication number: GB2125972A
Application number: GB08224318A
Authority: GB
Inventors: Alan James Checkland Park
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-08-25
Filing date: 1982-08-25
Publication date: 1984-03-14

Abstract

A voltage and continuity tester, provides five electrical testing functions through the use of a single piece of circuitry containing only one transistor and one indication lamp to test:- a) The presence of 240 volt a.c. mains b) The presence of low d.c. voltage approx: 1.5 to 5 volts. c) The presence of low d.c. voltage approx: 6 to 15 volts. d) Continuity through external circuit elements or components possessing from zero to approximately 200 ohms resistance. e) Continuity through external circuit elements or components possessing from zero to approximately 8,000 ohms resistance. The single transistor drives a single indicator lamp biased in three different ways corresponding to the provision of the three testing functions a), b) and e) listed above. The circuitry associated with these three tests is then combined with other circuit elements to provide all the five testing functions listed above. <IMAGE>

Description

SPECIFICATION Domestic electrical tester Relevant technical field The invention offers to the householder the opportunity to carry out a range of simple diagnostic tests on every day electrical apparatus around the home.

Background to the invention A standard electrical 'multi-meter' more normally possessed by an electrician or electronics enthusiast will perform all the functions of the invention and others beside.

However, the complexity of construction and the effective interpretation of readings associated with a multi-meter render the device outside the understanding and need of most people. Their need is not to define an absolute value of electrical voltage, current or resistance but more simply to identify a sound or unsound condition in an electrical component or unit to give direction to their future action. Whilst there are a number of simple items of domestic test equipment in existance for testing single functions e.g. neon screwdriver for testing the presence of live terminals carrying 240v a.c. mains, the invention provides circuitry and an arrangement of standard components which enable five separate testing functions to be achieved.These five functions used individually or in combination enable diagnostic checks to be made on a wide variety of everyday electrical components and apparatus.

Description of the invention The invention offers in a single piece of apparatus five individual electrical testing functions utilising a single indicator lamp and a single transistor. The five tests, lettered A to E on the circut diagram and general arrangement drawings perform the following functions: Test A-With connecting leads plugged into terminals "A", an indication of 240v a.c.

mains is provided by the illumination of the indicator lamp.

Test B-This test indicates the presence of low d.c. voltages up to about 5 volts and would be used for indicating whether small batteries possess any terminal voltage. Any voltage above about one volt will illuminate the indicator lamp.

Test C-This test indicates the presence of voltages in the range approximately 6 to 1 5 volts d.c. pro rata to indicator lamp brightness and this test would have particular use for general checks associated with motor car electrical systems.

Test D-This test provides a simple continuity check and the indicator lamp will illuminate fully when connecting leads are joined to a short circuit. The brightness of the indicator light will progressively weaken as additional resistance is applied by the external circuit, becoming completely extinguished when the resistance value reaches approximately 200 ohms. This test can therefore be used for testing fuses, leads and low resistance circuit elements including heaters, lamps, motors etc.

Test E-This test offers a similar function to Test D but will indicate continuity through an electrical circuit of up to approximately 8,000 ohms. This test would be used for testing higher resistive circuit elements e.g.

low wattage devices -- lamps, electric blankets etc.

Circuit behaviour for each test Test Mains voltage is rectified using a single diode and is fed into a potential divider which introduces sufficient bias voltage to the base of the transistor to make it conduct.

The resistor marked "x" on the circuit diagram is chosen to be of sufficiently high value not to switch on the transistor as in the mode used for Test E in the absence of mains voltage.

Test B-A small d.c. voltage provided by a sound battery to the terminals "B" will provide sufficient bias to switch on the transistor.

Correct polarity needs to be observed in this case.

Test C-In this mode, the transistor plays no part and an external voltage applied to terminals "C" is simply reduced in value to suit the indicator lamp through a series resistance.

Test D-As for test "C", the transistor plays no part in the circuit. External short-circuit or low resistance applied to terminals "D" merely complete a circuit through the battery and the indicator lamp.

Test E-For this test, the transistor is biased to switch on by the externally introduced resistance offered through connecting leads attached to terminals "E".

Circuit diagram and form of construction of tester Circuit diagram showing the single transistor and the single indicator lamp used in the invention is attached to this specification, Fig. 1.

The invention is best contained within a plastic box to protect the user from live circuit elements when using Test "A". Separate pairs of terminals for each test are preferred to the use of a single pair of terminals and a rotary selector switch for the purposes of greater reliability and simplicity of construction. A general layout arrangement for the front panel of the invention is given in Fig. 2.

Claims

1. The first claim of the invention is to use circuitry containing not more than one transistor and one indicating lamp to provide the three electrical testing functions of: a) Mains 240v a.c. indication.

b) Low d.c. voltage indication -- 1.5 to 5 volts.

c) Continuity through external circuit elements or components possessing from zero to approximately 8,000 ohms resistance.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Domestic electrical tester Relevant technical field The invention offers to the householder the opportunity to carry out a range of simple diagnostic tests on every day electrical apparatus around the home. Background to the invention A standard electrical 'multi-meter' more normally possessed by an electrician or electronics enthusiast will perform all the functions of the invention and others beside. However, the complexity of construction and the effective interpretation of readings associated with a multi-meter render the device outside the understanding and need of most people. Their need is not to define an absolute value of electrical voltage, current or resistance but more simply to identify a sound or unsound condition in an electrical component or unit to give direction to their future action. Whilst there are a number of simple items of domestic test equipment in existance for testing single functions e.g. neon screwdriver for testing the presence of live terminals carrying 240v a.c. mains, the invention provides circuitry and an arrangement of standard components which enable five separate testing functions to be achieved.These five functions used individually or in combination enable diagnostic checks to be made on a wide variety of everyday electrical components and apparatus. Description of the invention The invention offers in a single piece of apparatus five individual electrical testing functions utilising a single indicator lamp and a single transistor. The five tests, lettered A to E on the circut diagram and general arrangement drawings perform the following functions: Test A-With connecting leads plugged into terminals "A", an indication of 240v a.c. mains is provided by the illumination of the indicator lamp. Test B-This test indicates the presence of low d.c. voltages up to about 5 volts and would be used for indicating whether small batteries possess any terminal voltage. Any voltage above about one volt will illuminate the indicator lamp. Test C-This test indicates the presence of voltages in the range approximately 6 to 1 5 volts d.c. pro rata to indicator lamp brightness and this test would have particular use for general checks associated with motor car electrical systems. Test D-This test provides a simple continuity check and the indicator lamp will illuminate fully when connecting leads are joined to a short circuit. The brightness of the indicator light will progressively weaken as additional resistance is applied by the external circuit, becoming completely extinguished when the resistance value reaches approximately 200 ohms. This test can therefore be used for testing fuses, leads and low resistance circuit elements including heaters, lamps, motors etc. Test E-This test offers a similar function to Test D but will indicate continuity through an electrical circuit of up to approximately 8,000 ohms. This test would be used for testing higher resistive circuit elements e.g. low wattage devices -- lamps, electric blankets etc. Circuit behaviour for each test Test Mains voltage is rectified using a single diode and is fed into a potential divider which introduces sufficient bias voltage to the base of the transistor to make it conduct. The resistor marked "x" on the circuit diagram is chosen to be of sufficiently high value not to switch on the transistor as in the mode used for Test E in the absence of mains voltage. Test B-A small d.c. voltage provided by a sound battery to the terminals "B" will provide sufficient bias to switch on the transistor. Correct polarity needs to be observed in this case. Test C-In this mode, the transistor plays no part and an external voltage applied to terminals "C" is simply reduced in value to suit the indicator lamp through a series resistance. Test D-As for test "C", the transistor plays no part in the circuit. External short-circuit or low resistance applied to terminals "D" merely complete a circuit through the battery and the indicator lamp. Test E-For this test, the transistor is biased to switch on by the externally introduced resistance offered through connecting leads attached to terminals "E". Circuit diagram and form of construction of tester Circuit diagram showing the single transistor and the single indicator lamp used in the invention is attached to this specification, Fig. 1. The invention is best contained within a plastic box to protect the user from live circuit elements when using Test "A". Separate pairs of terminals for each test are preferred to the use of a single pair of terminals and a rotary selector switch for the purposes of greater reliability and simplicity of construction. A general layout arrangement for the front panel of the invention is given in Fig. 2. Claims 1. The first claim of the invention is to use circuitry containing not more than one transistor and one indicating lamp to provide the three electrical testing functions of: a) Mains 240v a.c. indication. b) Low d.c. voltage indication -- 1.5 to 5 volts. c) Continuity through external circuit elements or components possessing from zero to approximately 8,000 ohms resistance. 2. The second claim of the invention is to combine the circuitry achieving the testing functions specified above in Claim 1 with further circuit components to give two further test functions: e) Low d.c. voltage indication -- to 1 5 volts approximately. f) Continuity through external circuit elements or components possessing from zero to approximately 200 ohms resistance to give a total of five separate test functions in one piece of circuitry containing only one indicating lamp, one transistor and one semiconductor device. New claims or amendments to claims filed on 27.9.83 Superseded claims 1 and 2 New or amended claims

1. The first claim of the invention is to provide a range of AC/DC voltage and continuity electrical test functions appropriate to general domestic and automotive use using a single indicator light and supporting semiconductor based circuitry.

2. The second claim of the invention is to provide the following specific test functions: a) Mains supply indication in the range 110- 250 volts A.C.

b) D.C. Volts in the range 1.1 to 5 volts (specifically for testing useful life in single

1.5 volt cells - no indication at leass than

1.1 volts approximately).

c) D.C. Volts in the range 6 to 1 5 volts.

d) Continuity through electrical components/elements having internal resistance in the range zero to 200 Ohms approx.

e) Continuity through electrical components/eiements having internal resistance in the range zero to 8,000 Ohms approx.

3. The third claim of the invention is to achieve the Claims 1 and 2 above with the use of only a single transistor of either PNP or NPN type and a single semiconductor diode.

4. The fourth claim of the invention is to contain the device in a simple box having a single indicator light and five double sockets into which a double pin plug is inserted connected to two flying test leads/probes.