Temperature controlled magnetic permeability detector

Abstract

A device for detection of magnetic permeability () or, alternatively, relative magnetic permeability (r) or, alternatively relative magnetic susceptibility (r-) of a sample is described. The device comprises a sample chamber having at least one opening for introduction of a sample or a sample container holding a sample and an electronic circuit. The device also comprises a coil surrounding said sample chamber, and also an electronic circuit adapted to measure the inductance of said coil. The sample chamber, coil and at least one component of the electronic circuit are placed in a temperature controlled zone. Said at least one component in said electronic circuit is/are selected from the group consisting of capacitors, sensors, precision voltage references, precision regulators, low pass and or high pass filters.

Claims

1. A device for detection of magnetic permeability () or, alternatively, relative magnetic permeability (r) or, alternatively relative magnetic susceptibility (r-1) of a sample, said device comprising a sample chamber having at least one opening for introduction of a sample or a sample container holding a sample, said device also comprising a coil surrounding said sample chamber, and also comprising an electronic circuit adapted to measure the inductance of said coil, wherein said sample chamber, said coil, at least one heat sensor and at least one component in said electronic circuit are placed in a temperature controlled zone, wherein said at least one component in said electronic circuit is/are selected from the group consisting of capacitors, sensors, precision voltage references, precision regulators, low pass and or high pass filters and wherein said coil in the tempersature controlled zone is heated by a heat resistor.

2. The device according to claim 1, wherein all capacitors, sensors, precision voltage references, precision regulators, low pass and or high pass filters of the electronic circuit are placed in the temperature controlled zone.

3. The device according to claim 1, wherein said coil, when filled with air, has an inductance in the range of 0.01 to 100 H.

4. The device according to claim 1, wherein said sample chamber has a chamber volume of 0.1 to 5000 l.

5. The device according to claim 1, wherein said sample chamber is made of a polymer, wood, glass, or a metal with 0.999<r<1.001.

6. The device according to claim 5, wherein the polymer is chosen from the group consisting of polyoxymethylene, polyvinyl chloride, Teflon, polyamide, polyacetal, polyethylene, polycarbonate, polystyrene, or polypropylene.

7. The device according claim 1, wherein the device is suitable for detection of chemical substances.

8. The device of claim 7, wherein the chemical substances are selected from the group consisting of proteins, hormones, complement factors, bacteria, cells, viruses, fungi, yeast, spores, phages, cell organelles, DNA and RNA.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a basic diagram showing an example of an electronic circuit for measurement of magnetic permeability, wherein no temperature controlled zone is present.

(2) FIG. 2 is a basic diagram showing an example of an electronic circuit for measurement of magnetic permeability, wherein the electronic circuit is subject to a temperature controlled zone.

(3) The right side circuit shows a temperature control circuit, which circuit controls the temperature of the coil L2 of the left side circuit, keeping the temperature at the given set point temperature. By this temperature control, the output of the differential amplifier 104 is not affected by any temperature variation of the coil L2, thus giving a more sensitive and accurate result.

(4) FIG. 3 shows diagrams showing the characteristics of the measurements of a device for quantification of magnetic permeability, wherein the electronic circuit is not subject to a temperature controlled zone (left column), and also showing the characteristics of the measurements of a device according to the present invention wherein the electronic circuit is subject to a temperature controlled zone (right column).

(5) FIG. 4 shows schematically a device according to the present invention, where A is a coil, B is a temperature controlled zone of the electronic circuit, C is a non temperature controlled zone of the electronic circuit, D, D, D are electronic components in a temperature controlled zone, and E, E, E are electronic components in a non temperature controlled zone.

DETAILED DESCRIPTION OF THE INVENTION

(6) As stated above, the present invention relates to a device for detection of magnetic permeability () or, alternatively, relative magnetic permeability (r) or, alternatively relative magnetic susceptibility (r-1) of a sample, said device comprising a sample chamber having at least one opening for introduction of a sample or a sample container holding a sample, said device also comprising a coil surrounding said sample chamber, and also comprising an electronic circuit adapted to measure the inductance of said coil, wherein said sample chamber, said coil and at least one component in said electronic circuit are placed in a temperature controlled zone and wherein said at least one component in said electronic circuit is/are selected from the group consisting of capacitors, sensors, precision voltage references, precision regulators, low pass and or high pass filters.

(7) Not all types of electronic components may be placed in a temperature controlled zone. Coils, capacitors, sensors, precision voltage references, precision regulators, low pass and high pass filters are suitable for placing in a temperature controlled zone, while for instance A/D converters are disturbed by the current, and therefore should be placed further away from analogous signals.

(8) When power is applied to the device according to the present invention a voltage reference IC2 has the same temperature as a set point temperature given to the coil L2. The heat sensor IC1 has the actual temperature of the coil. This forces the output of IC3 to be at its highest voltage level as long as the difference between the set point temperature and the actual temperature value is above zero. As the heat resister warms the coil L2, the difference between the set point temperature and the actual temperature decreases until the actual temperature reaches the set point temperature, where no more heat needs to be provided until the actual temperature decreases, and there is a difference between the set point temperature and the actual temperature again.

(9) The coil L2 is preferably coated with an aluminum coating, to which the sensor IC1 and the heat resister R24, are attached.

(10) The sensor IC1 is a precision integrated-circuit temperature sensor which is connected to the aluminum coating of the coil L2. The output voltage of IC1 is linearly proportional to the temperature in degrees Celsius of the coating of the coil L2.

(11) IC2 is a voltage reference circuit, giving the set point temperature of the coating of the coil L2.

(12) IC3 is a circuit that compares the set point temperature (set by IC2) and the output voltage of IC1, thereby deciding if heating of the coating of the coil L2 is necessary or not.

(13) Thus, by providing a temperature control/regulation the output signal will be independent of the variation of the coil temperature and thus more accurate.

(14) In FIG. 3 the left columns show diagrams showing the characteristics of the measurements of a device for quantification of magnetic permeability wherein the electronic circuit is not subject to additional temperature control. Diagram A shows the long term drift in off-set versus time/number of measurements. Diagram B shows the imprecision of the measurements of off-set using an inorganic salt aqueous standard. Diagram C shows the imprecision versus off-set (long term drift in offset). Diagram D shows the imprecision versus offset at three different temperatures 17 C., 23 C., 27 C.

(15) In FIG. 3, the right columns show the characteristics of the measurements of a device according to the present invention wherein the electronic circuit is subject to an additional temperature control according to the present invention. Diagram E shows the long term drift in off-set versus time/number of measurements. Diagram F shows the imprecision of the measurements of off-set using an inorganic salt aqueous standard. Diagram G shows the shows the imprecision versus off-set (long term drift in off-set). Diagram H shows the imprecision versus offset in three different temperatures 17 C., 23 C., 27 C.

(16) The device according to the present invention can advantageously be used for detection of chemical substances. Preferably the chemical substances have a r=1. The chemical substances to be detected may be chosen from the group consisting of proteins, hormones, complement factors, bacteria, cells, viruses, fungi, yeast, spores, phages, cell organelles, DNA and RNA.