GB2202337A - Hall effect meters - Google Patents
Hall effect meters Download PDFInfo
- Publication number
- GB2202337A GB2202337A GB08702561A GB8702561A GB2202337A GB 2202337 A GB2202337 A GB 2202337A GB 08702561 A GB08702561 A GB 08702561A GB 8702561 A GB8702561 A GB 8702561A GB 2202337 A GB2202337 A GB 2202337A
- Authority
- GB
- United Kingdom
- Prior art keywords
- hall effect
- probe
- current
- magnetic field
- hall
- 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
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R21/00—Arrangements for measuring electric power or power factor
- G01R21/08—Arrangements for measuring electric power or power factor by using galvanomagnetic-effect devices, e.g. Hall-effect devices
Abstract
In a Hall effect meter for measuring energy passing along a conductor (1), a circuit (4) for supplying current to a Hall probe (3) comprises means (12, 13) for reversing the current to the probe. A measuring circuit (5) stores the outputs for the two current directions, and one value is subtracted from the other to obtain an output independent of self-field effects. The output when the probe is shorted may be subtracted from the output when it is not shorted to eliminate drift effects (Fig. 4 not shown). The current through the probe can also be increased (Figs. 5, 6 not shown) to compensate for temperature. A stabilising system (Fig. 7 not shown) maintains the temperature of the Hall effect device substantially constant. <IMAGE>
Description
MAGNETIC FIELD METER
The present invention relates to a magnetic field meter for use in for example an electrical energy consumption meter.
Conventional electrical consumption energy meters comprise an electro-mechanical arrangement of proven accuracy and reliability. The known meters are however relatively bulky and expensive and cannot easily be integrated into electronic signalling systems, for example remote meter reading systems.
It would be highly advantageous to provide an electronic rather than electro-magnetic energy consumption meter but it is difficult to provide a suitable circuit of acceptable reliability and accuracy. Given that the meter readings are used as the basis for charges to consumers connected to an electrical utility there is a reluctance on the part of such utilities to switch from electro-magnetic to electronic metering units if there is any question that the electronic metering units will be subject to inaccuracies over the many years that such units will be in the field.
Electronic energy consumption meters which rely upon Hall effect probes to monitor energy being consumed have been proposed in the past but problems have been experienced in obtaining the necessary degree of accuracy. It is known that the output derived from a Hall effect probe can be effected by a variety of factors, for example the self-field effect, short and long term drift effects, and temperature instability.
The self-field effect is due to the occurence of a small DC voltage appearing across the output of the
Hall effect probe and arising from a non-uniform current density distribution in the conductor of the
Hall effect probe. Short and long term drift effects are not often experienced in the Hall effect probe itself but can occur in measuring circuitry connected to the Hall effect probe. Temperature instability arises as a result of variations in the Hall effect probe resistance and solid state processes within the probe with variations in temperature. As energy consumption meters must be capable of operating accurately in a wide range of different environments significant temperature instability cannot be to-lerated.
It is an object of the present invention to provide a magnetic field meter which is capable of overcoming one or more of the above problems.
According to the present invention there is provided a magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the
Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output related to the measured electric field, wherein the supply circuit comprises means for reversing the current supply to the Hall effect probe, and wherein the measuring circuit comprises means for storing the measurement output when the supply current is in one direction, means for storing the measurement output when the supply current is in the opposite direction, and means for subtracting one of the stored measurement outputs from the other to obtain an output which is independent of self-field effects.
The abovedescribed meter provides an output independent of self-field effect because the voltage appearing across the terminals of the Hall probe as a result of self-field effects is always in the same direction regardless of the direction of the current supplied to the Hall effect probe.
The present invention also provides a magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output related to the measured electric field, wherein the measuring circuit comprises means for periodically shorting out the electric field developed across the Hall effect probe, means for storing the measurement output when the electric field is shorted out, and means for subtracting the stored output from the measurement output when the electric field is not shorted out to obtain an output which is independent of electrical drift effects.
In the above meter any long or short term drift effects which occur in the measuring circuit are fully taken into account in the measurement output which is stored when the output of the Hall effect probe is shorted out.
The present invention also provides a magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output relating to the measured electric field, wherein the supply circuit is provided with means for increasing the current supplied to the Hall effect probe to compensate for increases in Hall effect probe temperature.
Changes in the resistance of the Hall effect probe due to variations in temperature can be compensated for simply by maintaining the current through the probe constant. This can be achieved for example by connecting the Hall effect probe in a feedback path of an operational amplifier such that the gain of the amplifier is dependent upon the resistance of the Hall effect probe, and controlling the voltage supplied to the input of the operational amplifier and hence one terminal of the Hall effect probe in dependence on the output voltage of the operational amplifier. It has been discovered however that there are solid state processes within the Hall affect probe which vary with temperature and which also effect the Hall probe output voltage though to a lesser extent than simple resistance effects.To compensate for these solid state process changes it is necessary as outlined above to increase the current through the Hall effect probe as the Hall effect probe temperature increases.
The necessary increase in Hall effect probe current can be achieved by connecting the Hall effect probe in series with a thermistor having a negative temperature coeffecient and supplying current to the series connected components from a stabilised voltage source. The temperature coefficient of the thermistor is such that as the temperature of the thermistor and the Hall probe increases the resistance of the thermistor decreases more rapidly than the resistance of the Hall probe increases with the result that the current through the Hall probe increases with increases in temperature.
Alternatively the Hall probe can be connected in parallel with a thermistor having a positive temperature coefficient, the parallel connected components being connected to a constant current source. As the temperature increases the resistance of the thermistor increases more rapidly than the resistance of the Hall probe and as a result a greater proportion of the constant current supplied passes through the Hall probe.
The present invention also provides a magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output related to the measured electric field, wherein the Hall effect probe comprises a metallic base in thermal contact with a sheet of thermally conductive material, at least one Peltier device is mounted on the sheet of thermally conductive material, means are provided for sensing the temperature of the Hall effect device, and an electrical input to the Peltier device is controlled in dependence upon the sensed temperature to maintain the temperature of the Hall effect device substantially constant.
The term 'Peltier device' is used to indicate a device which relies on the Peltier effect to either generate or absorb heat at the junction between two dissimilar metals in dependence upon the direction of current through the junction.
The sheet of thermally conductive material may be in the form of a sheet of alumina. The temperature can be sensed by one or more thermocouples directly mounted on the sheet, or directly by monitoring the temperature dependent resistance of the Hall effect device itself.
Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Fig. 1 is a schematic illustration of an energy meter comprising a Hall effect probe and associated circuits and components;
Fig. 2 is a schematic block diagram of a conventional Hall effect energy meter;
Fig. 3 is a schematic block diagram of a Hall effect energy meter embodying one aspect of the present invention;
Fig. 4 is a schematic block diagram of a Hall effect energy meter embodying a second aspect of the present invention;
Figs. 5 and 6 are schematic block diagrams of alternative circuits embodying the third aspect of the present invention; and
Fig. 7 is a schematic illustration of a device embodying a fourth aspect of the present invention.
Referring to Fig. 1, the illustrated arrangement is intended to measure the electrical energy passing along a conductor 1. The conductor 1 passes through a magnetic core 2 which defines a small gap into which a Hall effect probe 3 is inserted. The Hall effect probe 3 is supplied with current by a supply circuit 4. When current passes down the conductor 1 a magnetic field is generated in the gap of the core and as a result an electric field is developed in a direction perpendicular to the current passing through the Hall probe. The electric field is monitored by a measuring circuit 5. The output of the Hall probe applied to the measuring circuit is proportional to the magnetic field induced in the coil and to the current supplied to the Hall probe from the supply circuit. Accordingly as has already been proposed it is possible to derive a measure of power from the Hall probe.
Referring now to Fig. 2, the illustrated arrangement operates in accordance with known principles to provide a measure of power consumed, the output of the Hall probe 3 being proportional to power. The Hall probe output is applied via an instrumentation amplifier 6 and a multiplexer 7 to an analogue to digital converter 8. The output of the analogue to digital converter 8 is applied to a microprocessor 9 which is controlled by data stored in an EPROM 10. The microprocessor operates to convert the information received from the Hall effect probe 3 into a measure of power consumed, for example the number of standard units of power consumed or the charge to be made for that power. The accumulated power consumed is displayed on a conventional display device 11.
Referring now to Fig. 3, an embodiment of one aspect of the present invention is illustrated. The arrangement of Fig. 3 is identical to that of Fig. 2 except for the addition of a double throw double pole switch 12 which is controlled by an input 13 provided by the microprocessor 9. The arrangement of Fig. 3 is intended to obviate problems which can result from the self-field effect which generates a small self-field voltage which is added to the desired Hall probe output. The self-field voltage is always in the same direction regardless of the direction of the drive current provided by the supply circuit 4.
Accordingly, in accordance with the present invention it is possible to cancel out the effects of the self-field voltage by monitoring the change in the output of the Hall element resulting from reversal of the supply current.
The arrangement of Fig. 3 operates such that the microprocessor 9 periodically actuates the switch 12 so as to reverse the supply current to the Hall probe 3. The microprocessor stores the measurement signal provided to it by the converter 8 both before and after actuation of the switch 12. The two measurement signals will differ by twice the self-field effect and accordingly subtracting one stored measurement value from the other and dividing the total by two a measurement signal independent of the self-field effect can be obtained and output to the display 11.
Referring now to Fig. 4, the illustrated arrangement is identical to that of Fig. 2 except for the addition of a single pole single throw switch 14 controlled by an input 15 provided by the microprocessor 9. The arrangement of Fig. 4 is intended to obviate the problems of short and long term drift. The illustrate arrangement compensates for any drift occurring in the measurement circuit 5.
The arrangement of Fig. 4 operates such that the microprocessor 9 periodically actuates the switch 14 to short out the output of the Hall effect probe such that the input to the measurement circuit is zero.
The microprocessor 9 stores the output of the converter 8 when the Hall probe is shorted out, the stored value corresponding to the total effect of any drift which might have occurred in any of the components of the measuring circuit. The
Fig. 6 illustrates an alternative arrangement to that of Fig. 5. In the arrangement of Fig. 6 the supply circuit 4 comprises a constant current power supply and a positive temperature coefficient thermistor 17 is connected in parallel with the Hall probe. The thermistor 17 is selected so that it over-compensates for the increase in ohmic resistance of the Hall probe so that as the temperature increases a greater proportion of the constant supply current passes through the Hall probe, the increase in supply current compensating for the abovementioned solid state processors.
Fig. 7 illustrates a device for stabilising the temperature of a Hall effect device. The Hall device 18 is mounted between a pair of Peltier devices 19 and a pair of thermocouples 20 on an alumina substrate 21. The Hall effect device comprises a metallic base in good contact with the substrate 21.
Thus by controlling the Peltier devices in a feedback loop by the thermocouples the temperature of the Hall effect device can be maintained constant.
It will be appreciated that the four aspects of the present invention described above can be combined in a single meter to compensate for self-field effects, short and long term drift and temperature variations.
microprocessor then actuates the switch 14 back to its initial condition so that the signal it receives from the converter 8 corresponds to the desired measurement signal plus the signal resulting from drift in the measurement circuitry. The microprocessor then subtracts the stored value from the measurement signal received from the converter and displays the result of that subtraction process on the display 11. The microprocessor can be arranged to short out the Hall effect probe at regular intervals so as to repeatedly update the stored value, thereby taking account of both short and long term drift effects.
Referring now to Fig. 5, a circuit is illustrated for compensating for the effects of temperature changes on the output of the Hall probe 3. As the temperature of a Hall probe increases its ohmic resistance also increases. In addition however there are solid state processes within the Hall effect chip which tend to reduce the current through the probe and accordingly affect its output. To overcome these combined temperature related effects it is necessary in accordance with the present invention to increase the current supplied to the
Hall probe as the temperature increases. In the case of Fig. 5, this is achieved by arranging for the supply circuit 4 to be a stable voltage power supply. A thermistor 16 with a negative temperature coefficient is connected in series with the Hall probe, the reduction in the resistance of the thermistor over-compensating for the increase in the ohmic resistance of the Hall probe 3 so that the current through the Hall probe increases sufficiently to compensate for the abovementioned solid state processes.
Claims (8)
1. A magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the
Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output related to the measured electric field, wherein the supply circuit comprises means for reversing the current supply to the Hall effect probe, .and wherein the measuring circuit comprises means for storing the measurement output when the supply current is in one direction, means for storing the measurement output when the supply current is in the opposite direction, and means for subtracting one of the stored measurement outputs from the other to obtain an output which is independent of self-field effects.
2. A magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the
Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output related to the measured electric field, wherein the measuring circuit comprises means for periodically shorting out the electric field developed across the Hall effect probe, means for storing the measurement output when the electric field is shorted out, and means for subtracting the stored output from the measurement output when the electric field is not shorted out to obtain an output which is independent of electrical drift effects.
3. A magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the
Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output relating to the measured electric field, wherein the supply circuit is provided with means for increasing the current supplied to the Hall effect probe to compensate for increases in Hall effect probe temperature.
4. A magnetic field meter according to claim 3, wherein the Hall effect probe is connected in series with a thermistor having a negative temperature coeffecient, and current is supplied to the series connected components from a stabilised voltage source, the temperature coefficient of the thermistor being such that as the temperature of the thermistor and the Hall probe increases the resistance of the thermistor decreases more rapidly than the resistance of the Hall probe increases with the result that the current through the Hall probe increases with increases in temperature.
5. A magnetic field meter according to claim 3, wherein the Hall probe is connected in parallel with a thermistor having a positive temperature coefficient, the parallel connected components being connected to a constant current source, the temperature coefficient of the thermistor being such that as the temperature increases the resistance of the thermistor increases more rapidly than the resistance of the Hall probe and as a result a greater proportion of the constant current supplied passes through the Hall probe.
6. A magnetic field meter comprising a Hall effect probe exposed to the magnetic field to be measured, a supply circuit for supplying current to the Hall effect probe, and a measuring circuit for measuring the electric field developed across the
Hall effect probe as a result of interaction between the magnetic field and the supplied current and for providing a measurement output related to the measured electric field, wherein the Hall effect probe comprises a metallic base in thermal contact with a sheet of thermally conductive material, at least one Peltier device is mounted on the sheet of thermally conductive material, means are provided for sensing the temperature of the Hall effect device, and an electrical input to the Peltier device is controlled in dependence upon the sensed temperature to maintain the temperature of the Hall effect device substantially constant.
7. A magnetic field meter according to claim 6, wherein the sheet of thermally conductive material is in the form of a sheet of alumina.
8. A magnetic field meter substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8702561A GB2202337B (en) | 1987-02-05 | 1987-02-05 | Magnetic field meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8702561A GB2202337B (en) | 1987-02-05 | 1987-02-05 | Magnetic field meter |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8702561D0 GB8702561D0 (en) | 1987-03-11 |
| GB2202337A true GB2202337A (en) | 1988-09-21 |
| GB2202337B GB2202337B (en) | 1991-10-16 |
Family
ID=10611749
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8702561A Expired - Lifetime GB2202337B (en) | 1987-02-05 | 1987-02-05 | Magnetic field meter |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2202337B (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2236399A (en) * | 1989-09-22 | 1991-04-03 | Bartington Instr Ltd | Telemetry apparatus for magnetic flux sensors |
| EP0438637A1 (en) * | 1990-01-24 | 1991-07-31 | Landis & Gyr Business Support AG | Method and apparatus for the determination of an effective value Ieff of a current to be measured using a Hall element and an amplifier circuit |
| GB2243222A (en) * | 1990-04-17 | 1991-10-23 | John Dudding | Drift correction in integrators |
| DE4028614A1 (en) * | 1990-09-08 | 1992-03-12 | Emh En Messtechnik Gmbh | Measuring large currents with electricity meter - using Hall element in slotin annular ferrite core with main conductor forming current loop |
| US6545456B1 (en) * | 1998-08-12 | 2003-04-08 | Rockwell Automation Technologies, Inc. | Hall effect current sensor package for sensing electrical current in an electrical conductor |
| DE3933707B4 (en) * | 1988-10-10 | 2004-02-26 | Iskra Stevci Industrija Merilne In Upravljalne Tehnike Kranj, D.O.O. | Circuit for compensating temporal instabilities of the multiplication circuit with Hall sensors in a wattmeter or electricity meter |
| RU2806889C1 (en) * | 2023-05-19 | 2023-11-08 | Сюньпэн Чжан | Method and device for capturing signal arising from nernst-ettinghausen effect in superconductor |
-
1987
- 1987-02-05 GB GB8702561A patent/GB2202337B/en not_active Expired - Lifetime
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3933707B4 (en) * | 1988-10-10 | 2004-02-26 | Iskra Stevci Industrija Merilne In Upravljalne Tehnike Kranj, D.O.O. | Circuit for compensating temporal instabilities of the multiplication circuit with Hall sensors in a wattmeter or electricity meter |
| GB2236399A (en) * | 1989-09-22 | 1991-04-03 | Bartington Instr Ltd | Telemetry apparatus for magnetic flux sensors |
| GB2236399B (en) * | 1989-09-22 | 1994-05-25 | Bartington Instr Ltd | Telemetry |
| EP0438637A1 (en) * | 1990-01-24 | 1991-07-31 | Landis & Gyr Business Support AG | Method and apparatus for the determination of an effective value Ieff of a current to be measured using a Hall element and an amplifier circuit |
| GB2243222A (en) * | 1990-04-17 | 1991-10-23 | John Dudding | Drift correction in integrators |
| DE4028614A1 (en) * | 1990-09-08 | 1992-03-12 | Emh En Messtechnik Gmbh | Measuring large currents with electricity meter - using Hall element in slotin annular ferrite core with main conductor forming current loop |
| US6545456B1 (en) * | 1998-08-12 | 2003-04-08 | Rockwell Automation Technologies, Inc. | Hall effect current sensor package for sensing electrical current in an electrical conductor |
| RU2806889C1 (en) * | 2023-05-19 | 2023-11-08 | Сюньпэн Чжан | Method and device for capturing signal arising from nernst-ettinghausen effect in superconductor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8702561D0 (en) | 1987-03-11 |
| GB2202337B (en) | 1991-10-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |