Hall effect measurement instrument with temperature compensation
View Patent ↗Disclosed is a Hall Effect instrument with the capability of compensating for temperature drift consistently, accurately and in real time of operation. The instrument embodies a four-point ohm meter circuit measuring Hall Effect sensor resistance and tracking the effect of temperature on the Hall Effect sensor. The instrument takes into account a relationship between the temperature and a temperature compensation index on a per probe basis, which has exhibited a deterministic difference observed by the present inventor.
1. An instrument measuring Hall Effect of at least one Hall sensor magnetically coupled with a target during a measurement session, comprising:
a probe including the Hall sensor, a magnetic field source and a temperature sensor configured to provide a probe temperature reading on or at a very close proximity of the magnetic field source;
a data processing and display console coupled with the probe at a predetermined distance with an electronic coupling means, the console further comprising,
a Hall Effect measurement circuit connected with the Hall sensor via the coupling means, the Hall Effect measurement circuitry further including at least partially a Four-Wire Ohm Meter circuit, which captures at least two pairs of differential signals from the Hall Effect sensor,
a data acquisition and processing module configured to receive signals from the Hall Effect measurement circuit and provide at least two pairs of uncompensated raw based on the differential signals;
a temperature compensation module configured to compute based on the at least two pairs of uncompensated raw data and the temperature reading and a probe slope associated with the probe to produce a temperature compensation index;
a measurement conversion module configured to provide a corrected Hall Effect measurement data by correcting the raw signal data using information corresponding to the temperature compensation index.
2. The instrument of claim 1 further comprises an electronic erasable memory for storing specific information in the probe.
3. The instrument of claim 1 is configured to measure thickness according to the strength of the Hall Effect measurement.
4. The instrument of claim 1 , wherein the compensation index is a result of dynamically compensating the Hall Effect measurement of the probe with the temperature change in the Hall sensor and/or at the magnetic source.
5. The instrument of claim 1 , wherein the two pairs of the uncompensated raw data, including raw Hall Effect Sense Voltage, V SNS — R and raw Hall Effect Monitor Voltage, V MON — R , respectively, wherein V SNS — R and V MON — R is each fed to the data acquisition and processing module.
6. The instrument of claim 5 wherein the data acquisition and processing module further comprises a data acquisition module and a signal processing module, wherein the signal processing module producing Hall Effect filtered digital sense voltage V SNS — R from the V SNS — R and filtered digital monitor voltage V MON — F from the V MON — R .
7. The instrument of claim 6 wherein the temperature compensation module further comprises a probe parameter temperature compensation module producing a first compensating factor V COMP — P , a probe slope temperature compensation module producing a second compensation factor V COMP — S and a probe temperature compensation index calculation module producing a temperature compensation index V COMP .
8. The instrument of claim 7 , wherein the Hall Effect measurement circuitry further comprises a voltage source providing substantially constant current source I SRC to the Four-Wire Ohm Meter circuit.
9. The instrument of claim 8 , wherein the probe parameter temperature compensation module further comprises probe parameter temperature compensation calculator producing the factor V COMP — P substantially according to the following:
V COMP — P =V SNS — F +V MON — F *(α+ V SNS — F *β)+ T mag(γ+ V SNS — F *δ) Eq. 1
wherein, Tmag is the temperature from the Temperature Sensor.
10. The instrument of claim 9 , wherein α, β, γ and δ are obtained according to Eq. 1, and empirical data from conducting experiments on the probe of each probe type, yielding readings of the V SNS — F , V MON — F , I SRC from the corresponding Four-Wire ohmmeter and the temperature reading, T mag for the probe.
11. The instrument of claim 7 , wherein the Hall Effect measurement circuitry further comprises a voltage source and a voltage source current stability monitoring circuit, providing a raw voltage differential data V IMON — R factored by the current monitoring circuit, wherein V IMON — R is further provided to the data acquisition and processing module.
12. The instrument of claim 11 , wherein the signal processing module further provides a filtered differential voltage data V IMON — P factored by the current monitoring circuit, based on the Hall Effect measurement value of raw voltage V IMON — R .
13. The instrument of claim 12 , wherein the probe parameter temperature compensation module further comprises an a probe parameter temperature compensation calculator producing the factor V COMP — P substantially according to the following:
V COMP — P =((( V SNS — F )+(( V MON — F −V IMON — F )* A )+((( V MON — F −V IMON — F )*( V SNS — F )* B )/( V IMON — F ))+(( T mag−22)*( V IMON — F )* C )+(( T mag−22)*( V SNS — F )* D ))/( V IMON — F )), Eq. 2
wherein A, B, C and D are all coefficient accounting for manufacturing tolerances of the probe and the Hall Effect sensor.
14. The instrument of claim 13 , wherein A, B, C and D are obtained according to Eq. 1, and empirical data from conducting experiments on the probe of each probe type, yielding readings of the V SNS — F , V MON — F , V IMON — F from the corresponding Four-Wire ohmmeter and the temperature reading, T mag for the probe.
15. The instrument of claim 7 wherein the probe parameter temperature compensation module further comprises a probe slope temperature compensation calculator producing the factor V COMP — S according to a probe slope derived according to experimental data collected on the probe,
V COMP — S =Probe Slope*( T mag−Reference Temperature) Eq. 3
wherein Tmag is the temperature reading.
16. The instrument of claim 15 , wherein the probe slope is stored in the electronic erasable memory.
17. The instrument of claim 7 , wherein the temperature compensation index calculation module calculates the temperature compensation index, deriving from the first compensation factor V COMP — P and the second compensation factor V COMP — S according to
Temperature Compensation Index V COMP =V COMP — P −V COMP — S Eq. 4.
18. The instrument of claim 17 , wherein the measurement conversion module is configured to produce the corrected Hall Effect measurement data based on the temperature compensation index V COMP for the probe and the target.