GB2155223A - A circuit - Google Patents

A circuit Download PDF

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Publication number
GB2155223A
GB2155223A GB08405296A GB8405296A GB2155223A GB 2155223 A GB2155223 A GB 2155223A GB 08405296 A GB08405296 A GB 08405296A GB 8405296 A GB8405296 A GB 8405296A GB 2155223 A GB2155223 A GB 2155223A
Authority
GB
United Kingdom
Prior art keywords
circuit
monitor device
resistor
monitor
resistance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08405296A
Other versions
GB2155223B (en
GB8405296D0 (en
Inventor
Adrian Hastings Lay
Dr Nigel Conrad George Preston
Richard Graham Woodhouse
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BL Technology Ltd
Original Assignee
BL Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BL Technology Ltd filed Critical BL Technology Ltd
Priority to GB08405296A priority Critical patent/GB2155223B/en
Publication of GB8405296D0 publication Critical patent/GB8405296D0/en
Publication of GB2155223A publication Critical patent/GB2155223A/en
Application granted granted Critical
Publication of GB2155223B publication Critical patent/GB2155223B/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/06—Monitoring of the line circuits, e.g. signalling of line faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/54—Testing for continuity

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)
  • Testing Of Engines (AREA)

Abstract

A circuit in which a high resistance monitor device, eg a piezo-electric crystal in a detonation detector or a spark ignition internal combustion engine, is connected to a sensor device. The integrity of the connection between the monitor device and the sensor device is verified by passing a current from the sensor device through the connection and through a resistor (Rx) connected across the output terminals of the monitor device. Changes in this current are sensed if an open circuit or short circuit occurs in the connection between the monitor device and the sensor device. The monitor device ES may generate an AC signal and this is sensed via capacitor CS. <IMAGE>

Description

SPECIFICATION A circuit This invention relates to a circuit for producing a warning signal if an open circuit o short circuit occurs in a connection between a monitor device and a sensor device.
In a circuit comprising a monitor device which has a high resistance or impedance it is difficult to determine whether a sensor device used to sense the output signals of the monitor device becomes disconnected from the monitor device since it is difficult to distinguish between signals from the monitor device and signals due to noise pick-up on the connection to the sensor device.
According to this invention there is provided a circuit comprising: a monitor device arranged to produce an output signal dependent upon a condition to be monitored and which exhibits a high resistance in at least some operating conditions; a resistor connected across the output terminals of the monitor device, the resistor having a relatively low resistance compared to the said resistance of the monitor device; and a sensor device remote from the monitor device but connected to the output terminals thereof, the sensor device comprising sensing means for sensing the output signal of the monior device, voltage means for applying a potential across the resistor, and detector means for detecting current flowing through the resistor and for producing a warning signal if the current changes due to a short circuit or open circuit in the connection between the sensor device and the resistor.
Preferred features of this invention will become apparent from the subsidiary claims of this specification.
This invention will now be described, merely by way of example, with reference to the accompanying drawings, in which: Figure 1 shows the equivalent circuit of a monitor device which comprises a piezo-electric crystal; Figure 2 shows a first embodiment of a circuit according to this invention; Figure 3 shows the relationship the level of the output signal of a monitor device of the circuit shown in Figure 2 and the frequency thereof; and Figure 4 shows a second embodiment of a circuit according to this invention.
Figure 1 shows the equivalent circuit of a piezo-electric crystal which may be used as an accelerometer to monitor detonation in a spark ignition internal combustion engine by monitoring the vibration thereof. In such a monitor device, a potential Es is induced across opposite faces of the piezo-electric crystal due to compression of the crystal between a body of the sensor device, which may be mounted on the engine, and a seismic mass. The potential Es induced across the crystal varies with the vibration of the engine and vibrations with a frequency within a particular band width indicate whether detonation occurs. The equivalent capacitance Cs and resistance Rs of such a device may be typically 1 nano Farad and 100 mega ohms respectively. The device therefore has a high impedance to DC current.
Figure 2 shows the equivalent circuit of a piezo-electric crystal as shown in Figure 1 connected in a first embodiment of a circuit according to this invention. The output signal Es of the piezo-electric crystal is sensed through an AC-coupler Cc which provides a signal Vin used to control operation of the engine so as to prevent detonation. The sensor device would, of course, include or be connected to further circuitry which is not illustrated to control the engine in dependance upon the signal Vin.
A resistor Rx having a resistance of approximately 1 mega ohm is connected between the output terminals of the piezo-electric crystal. A potential is applied across resistor Rx by means of a pull-up resistor Rp connected to a positive voltage V+. A transistor T is used to detect whether current is flowing through the resistor Rx. If current is flowing through the resistor Rx, the transistor T is switched ON so that an output voltage Vo thereof will be HIGH. If current is not flowing through the resistor Rx because the piezo-electric crystal has become disconnected from the sensor device, the transistor T will be switched OFF and the output signal Vo will be LOW. Thus, the output signal Vo can be used as a warning signal to indicate whether or not the sensor device is connected to the monitor device.
Figure 3 the relationship between the level of the output signal Es or the signal Vin and the frequency thereof. It will be seen that at lower frequencies the relationship is changed by the use of the resistor Rx.
However, the frequency band D which corresponds to the detection of detonation in the engine is unaffected by this change.
The circuit shown in Figure 2 is particularly suitable for use in a denotation detection device for controlling operation of a spark ignition internal combustion engine as it enables the integrity of the connection between the monitor device and the sensor device to be verified. Thus, if the sensor device becomes disconnected from the monitor device a warning signal is given to indicate that detonation of the engine is not being detected. It will be appreciated that an engine can be severely damaged if detonation occurs and steps or adjustments are not effected to prevent it.
This invention also relates to a spark ignition internal combustion engine having a circuit as described above and to a vehicle having such an engine.
Figure 4 shows a second embodiment of a circuit according to this invention. In the circuit illustrated in Figure 4, the monitor device comprises an electro-mechanical switch SW which may be used to indicate a change in external environment. In order to detect whether the switch is connected to the sensor device, resistors Ry and Rz are provided in parallel and in series with the switch SW respectively, the resistor Ry being connected between the output terminals of the switch SW. The sensor device is provided with a pull-up resistor Rp connected to a positive voltage V by means of which a current is passed through the resistors Ry and Rz. By detecting whether a current is flowing through these resistors, it can be determined whether an open circuit or a short circuit occurs in the connection between the monitor device and the sensor device.
When the monitor device is connected to the sensor device, the state of the switch SW is determined by detecting the voltage Vin: Switch open: Vin = V+ (RxcRy) R + Rx + Ry Switch closed: Vin = V+ Ry R + Ry If the monitor device becomes disconnected from the sensor device, Vin = V+ and if a short circuit occurs in the connection between the monitor device and the sensor device Vin = 0. Further circuitry which is not illustrated would, of course, be provided to sense the levels of Vin referred to above and to control operation of apparatus such as an internal combustion engine in dependence upon the levels of this voltage. It will be appreciated that if the resistors Ry,Rz and Rp were not provided it would be difficult to determine whether or not the sensor device was connected to the monitor device since in this situation Vin = 0 as it would if the switch SW were open.

Claims (9)

1. A circuit comprising: a monitor device arranged to produce an output signal dependent upon a condition to be monitored and which exhibits a high resistance in at least some operating conditions; a resistor connected across the output terminals of the monitor device, the resistor having a relatively low resistance compared to the said resistance of the monitor device; and a sensor device remote from the monitor device but connected to the output terminals thereof, the sensor device comprising sensing means for sensing the output signal of the monitor device, voltage means for applying a potential across the resistor, and detector means for detecting current flowing through the resistor and for producing a warning signal if the current changes due to a short circuit or open circuit in the connection between the sensor device and the resistor.
2. A circuit as claimed in claim 1 in which, in operation, the monitor device produces an alternating output signal and the voltage means causes a DC current to flow through the resistor.
3. A circuit as claimed in claim 2 in which the monitor device is a piezo-electric accelerometer for monitoring vibrations.
4. A circuit as claimed in claim 2 or 3 in which the sensing means comprises an AC coupler through which the output signal of the monitor device is sensed.
5. A circuit as claimed in any preceding claim in which the said resistance of the monitor device is of the order of 100 mega ohms and the resistance of the resistor is of the order of 1 mega ohm.
6. A circuit as claimed in any of claims 2 to 5 in which the monitor device is arranged to monitor detonation in a spark ignition internal combustion engine.
7. A circuit as claimed in claimed in claim 1 in which the monitor device comprises an ON-OFF switch which is actuated independence upon the condition to be monitored.
8. A circuit substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.
9. A vehicle having a spark ignition internal combustion engine as claimed in claim 8.
9. A spark ignition internal combustion engine having a circuit as claimed in claim 6.
10. A vehicle having a spark ignition internal combustion engine as claimed in claim 9.
Amendments to the claims have been filed, and have the following effect: Newortextually amended claims have been filed as follows:
1. A circuit comprising: a monitor device arranged to produce an alternating output signal dependent upon a condition to be monitored and which exhibits a high resistance in at least some operating conditions; a a resistor connected across the output terminals of the monitor device, the resistor having a relatively low resistance compared to the said resistance of the monitor device; and a sensor device remote from the monitor device but connected to the output terminals thereof, the sensor device comprising sensing means for sensing the output signal of the monitor device, voltage means for applying a potential across the resistor to cause a direct current to flow therethrough, and detector means for detecting current flowing through the resistor and for producing a warning signal if the current changes due to a short circuit or open circuit in the connection between the sensor device and the resistor.
2. A circuit as claimed in claim 1 in which the monitor device is a piezo-electric accelerometer for monitoring vibrations.
3. A circuit as claimed in claim 1 or 2 in whivh the sensing means comprises an AC coupler through which the output signal of the monitor device is sensed.
4. A circuit as claimed in any preceding claim in which the said resistance of the monitor device is of the order of 100 mega ohms and the resistance of the resistor is of the order of 1 mega ohm.
5. A circuit as claimed in any preceding claim in which the monitor device is arranged to monitor detonation in a spark ignition internal combustion engine.
6. A circuit as claimed in claim 1 in which the monitor comprises an ON-OFF switch which is actuated in dependence upon the condition to be monitored.
7. A circuit substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.
8. A spark ignition internal combustion engine having a circuit as claimed in claim 5.
GB08405296A 1984-02-29 1984-02-29 A circuit Expired GB2155223B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08405296A GB2155223B (en) 1984-02-29 1984-02-29 A circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08405296A GB2155223B (en) 1984-02-29 1984-02-29 A circuit

Publications (3)

Publication Number Publication Date
GB8405296D0 GB8405296D0 (en) 1984-04-04
GB2155223A true GB2155223A (en) 1985-09-18
GB2155223B GB2155223B (en) 1987-07-08

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB08405296A Expired GB2155223B (en) 1984-02-29 1984-02-29 A circuit

Country Status (1)

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GB (1) GB2155223B (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2595521A1 (en) * 1986-03-07 1987-09-11 Electricite De France TELECOMMUNICATION DEVICE
EP0249410A1 (en) * 1986-06-11 1987-12-16 VOLEX GROUP plc Manually operable electrical switches for use in information handling and control systems.
GB2194363A (en) * 1986-08-15 1988-03-02 Marathon Electric Mfg Alternator regulator
EP0353156A1 (en) * 1988-07-28 1990-01-31 Telemecanique Input circuit of the on or off type for a programmable automatic device
EP2239589A1 (en) * 2009-04-09 2010-10-13 Ascom (Sweden) AB Device, method and assembly for integrity checking of electrical wiring

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB910920A (en) * 1960-06-21 1962-11-21 Pyrene Co Ltd Improvements in or relating to fire-detection circuits
GB1548526A (en) * 1977-10-26 1979-07-18 Tronic Alarms Ltd M Burglar and fire alarm detection circuit monitor
EP0026461A2 (en) * 1979-09-28 1981-04-08 Siemens Aktiengesellschaft Circuit arrangement for intrusion or fire alarm systems
EP0026462A2 (en) * 1979-09-28 1981-04-08 Siemens Aktiengesellschaft Method and device for individual alarm identification in intrusion or fire alarm systems
GB2072911A (en) * 1980-03-06 1981-10-07 Contronic Controls Alarm system
EP0066879A1 (en) * 1981-06-05 1982-12-15 Hekatron GmbH Circuit arrangement for the transmission of measured values to a central station, especially for a fire signalling system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB910920A (en) * 1960-06-21 1962-11-21 Pyrene Co Ltd Improvements in or relating to fire-detection circuits
GB1548526A (en) * 1977-10-26 1979-07-18 Tronic Alarms Ltd M Burglar and fire alarm detection circuit monitor
EP0026461A2 (en) * 1979-09-28 1981-04-08 Siemens Aktiengesellschaft Circuit arrangement for intrusion or fire alarm systems
EP0026462A2 (en) * 1979-09-28 1981-04-08 Siemens Aktiengesellschaft Method and device for individual alarm identification in intrusion or fire alarm systems
GB2072911A (en) * 1980-03-06 1981-10-07 Contronic Controls Alarm system
EP0066879A1 (en) * 1981-06-05 1982-12-15 Hekatron GmbH Circuit arrangement for the transmission of measured values to a central station, especially for a fire signalling system

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2595521A1 (en) * 1986-03-07 1987-09-11 Electricite De France TELECOMMUNICATION DEVICE
EP0237419A1 (en) * 1986-03-07 1987-09-16 Electricite De France Remote meter-reading device
EP0249410A1 (en) * 1986-06-11 1987-12-16 VOLEX GROUP plc Manually operable electrical switches for use in information handling and control systems.
US4777378A (en) * 1986-06-11 1988-10-11 Salplex Limited Information handling and control systems, manually operable electrical switches for use in such systems, and methods of testing such switches in such systems
GB2194363A (en) * 1986-08-15 1988-03-02 Marathon Electric Mfg Alternator regulator
EP0353156A1 (en) * 1988-07-28 1990-01-31 Telemecanique Input circuit of the on or off type for a programmable automatic device
FR2634899A1 (en) * 1988-07-28 1990-02-02 Merlin Gerin INPUT CIRCUIT OF THE TYPE ALL OR NOTHING OF A PROGRAMMABLE AUTOMATE
EP2239589A1 (en) * 2009-04-09 2010-10-13 Ascom (Sweden) AB Device, method and assembly for integrity checking of electrical wiring
NL2002741C2 (en) * 2009-04-09 2010-10-13 Ascom Sweden Ab Device, method and assembly for integrity checking of electrical wiring.

Also Published As

Publication number Publication date
GB2155223B (en) 1987-07-08
GB8405296D0 (en) 1984-04-04

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Legal Events

Date Code Title Description
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
732E Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20010228