A current detection circuit includes an operational amplifier, a current sense amplifier including a first resistor and a second resistor, and a level shifter. The first resistor is provided between one end of a shunt resistor and a first input node of the operational amplifier. The second resistor is provided between the other end of the shunt resistor and a second input node of the operational amplifier. The level shifter controls voltages of the first input node and the second input node by controlling, according to a voltage at the one end of the shunt resistor, currents supplied to the first input node and the second input node.

A current sensor including: a sensing unit including one or more sensing elements, the sensing unit being arranged to generate, at least in part, an internal signal, the internal signal being generated in response to a magnetic field, the magnetic field being produced, at least in part, by an electrical current that is sensed with the sensing unit; a first signal processing path coupled to the sensing unit, the first signal processing path including a first compensation unit for adjusting the internal signal, the first signal processing path being configured to generate a first signal based on the internal signal; a second signal processing path coupled to the sensing unit, the second signal processing path including a second compensation unit for adjusting the internal signal, the second path having a different sensitivity than the first path.

A current detection module capable of differentiating and quantifying contribution to a current signal generated by a sensor in response to stimulation by a certain target source from contributions from sources other than the target source (ambient sources) is disclosed. As long as the contribution from the target source comprises a pulsed signal, the module may synchronize itself to the pulse(s) so that there is a predetermined phase relationship between the pulse(s) and functions carried out by various stages of the module. The module may be re-used to also detect and quantify contributions from ambient sources by presenting these contributions to the module as pulses that trigger synchronization of the module. To that end, a detection system disclosed herein is based on the use of such current detection module and allows mode switching where, depending on the selected mode of operation, the module is configured to perform different measurements.

Systems, methods, and apparatuses for determining pore volume and pore volume compressibility of secondary porosity in rock samples is disclosed. In some implementations, determining a pore volume of a secondary porosity in a rock core sample may include saturating the rock sample with deuterium oxide (D2O) by applying a vacuum to the core sample covered by D2O; centrifuging the saturated rock sample at a selected rotational speed in the presence of a second fluid to displace a portion of the D2O from the rock sample with the second fluid; measuring the rock sample with low-field .sup.1H nuclear magnetic resonance (NMR) to determine a volume of the second fluid within the rock sample; and determining a pore volume associated with a secondary porosity based on the volume of the second fluid within the rock sample.

Systems, methods, and apparatuses for determining pore volume and pore volume compressibility of secondary porosity in rock samples is disclosed. In some implementations, determining a pore volume of a secondary porosity in a rock core sample may include saturating the rock sample with deuterium oxide (D2O) by applying a vacuum to the core sample covered by D2O; centrifuging the saturated rock sample at a selected rotational speed in the presence of a second fluid to displace a portion of the D2O from the rock sample with the second fluid; measuring the rock sample with low-field .sup.1H nuclear magnetic resonance (NMR) to determine a volume of the second fluid within the rock sample; and determining a pore volume associated with a secondary porosity based on the volume of the second fluid within the rock sample.

In a method for measuring a current, a plurality of flux-gate field sensors is arranged with radial symmetry on a first circumferential path, and a plurality of Hall sensors is arranged with radial symmetry on a second circumferential path such that a one of the flux-gate field sensors is placed adjacent a one of the Hall sensors, with the flux-gate field sensors having a sensitivity which is higher by a factor 5 to 20 than a sensitivity of the Hall sensors. At least one of the plurality of flux-gate field sensors is evaluated so as to determine a current intensity, when two of the flux-gate field sensors generate measurement values within a measurement range, or at least one of the plurality of Hall sensors is evaluated so as to determine a current intensity, when the measurement values of the two flux-gate field sensors are outside of the measurement range.

In a method for measuring a current, a plurality of flux-gate field sensors is arranged with radial symmetry on a first circumferential path, and a plurality of Hall sensors is arranged with radial symmetry on a second circumferential path such that a one of the flux-gate field sensors is placed adjacent a one of the Hall sensors, with the flux-gate field sensors having a sensitivity which is higher by a factor 5 to 20 than a sensitivity of the Hall sensors. At least one of the plurality of flux-gate field sensors is evaluated so as to determine a current intensity, when two of the flux-gate field sensors generate measurement values within a measurement range, or at least one of the plurality of Hall sensors is evaluated so as to determine a current intensity, when the measurement values of the two flux-gate field sensors are outside of the measurement range.

A current measurement circuit may use a probabilistic technique to determine a current from a circuit block. In one embodiment, the circuit includes a comparator circuit, a first current sensing element (such as a first resistor), and a control circuit. The first current sensing element is coupled to the comparator circuit to establish a first comparator input signal representative of the current at an input of the comparator circuit. The control circuit is coupled to the comparator circuit to obtain a first plurality of comparator output decisions corresponding to the first current sensing element for a specified count, determine a first proportion of comparator output decisions meeting a specified criterion, and determine a voltage value of the first comparator input signal from the first proportion. The control circuit is configured to determine a current value using the voltage value of the first comparator input signal and an impedance value of the first current sensing element. The current measurement circuit is relatively low-cost and easy to implement, without requiring a precision reference voltage, current, and/or high-cost analog-to-digital converters (ADCs).

A current sensor integrated circuit (IC) includes a unitary lead frame having at least one first lead having a terminal end, at least one second lead having a terminal end, and a paddle having a first surface and a second opposing surface. A semiconductor die is supported by the first surface of the paddle, wherein the at least one first lead is electrically coupled to the semiconductor die and the at least one second lead is electrically isolated from the semiconductor die. The current sensor IC further includes a first mold material configured to enclose the semiconductor die and the paddle and a second mold material configured to enclose at least a portion of the first mold material, wherein the terminal end of the at least one first lead and the terminal end of the at least one second lead are external to the second mold material.

A current sensor integrated circuit (IC) includes a unitary lead frame having at least one first lead having a terminal end, at least one second lead having a terminal end, and a paddle having a first surface and a second opposing surface. A semiconductor die is supported by the first surface of the paddle, wherein the at least one first lead is electrically coupled to the semiconductor die and the at least one second lead is electrically isolated from the semiconductor die. The current sensor IC further includes a first mold material configured to enclose the semiconductor die and the paddle and a second mold material configured to enclose at least a portion of the first mold material, wherein the terminal end of the at least one first lead and the terminal end of the at least one second lead are external to the second mold material.