An HF olefin/isoparaffin alkylation process is carried out in an alkylation unit with a settling vessel in which the alkylate product is separated from the HF acid catalyst containing water and acid soluble oil (ASO). The density of the liquids in the settling vessel is measured at different levels by means of a nuclear density profile analyzer. The acid strength of the acid phase is determined from the density measurement and an optional temperature measurement. The proportion of water in the acid phase may also be measured separately by measurement of its electrical conductivity to determine the respective contributions of the water and the ASO to the density of the HF acid phase.

An HF olefin/isoparaffin alkylation process is carried out in an alkylation unit with a settling vessel in which the alkylate product is separated from the HF acid catalyst containing water and acid soluble oil (ASO). The density of the liquids in the settling vessel is measured at different levels by means of a nuclear density profile analyzer. The acid strength of the acid phase is determined from the density measurement and an optional temperature measurement. The proportion of water in the acid phase may also be measured separately by measurement of its electrical conductivity to determine the respective contributions of the water and the ASO to the density of the HF acid phase.

Systems and methods for measuring a temperature dependency of a threshold voltage are provided. Disclosed systems can include a shared pre-charge P-type metal-oxide-semiconductor (PMOS) transister, configured to pre-charge an output node to a supply voltage. The system can further include a sensing PMOS transistor, electrically coupled to the shared pre-charge PMOS transistor, configured to discharge the output node to a first voltage at or near the threshold voltage of the sensing PMOS transistor and measure a second voltage at the output node.

Systems and methods for measuring a temperature dependency of a threshold voltage are provided. Disclosed systems can include a shared pre-charge P-type metal-oxide-semiconductor (PMOS) transister, configured to pre-charge an output node to a supply voltage. The system can further include a sensing PMOS transistor, electrically coupled to the shared pre-charge PMOS transistor, configured to discharge the output node to a first voltage at or near the threshold voltage of the sensing PMOS transistor and measure a second voltage at the output node.

Methods of producing luminescence by application of a time-varying electrical signal to an electroluminescent device are disclosed whereby the entire system remains at open circuit. At least one article, substance or material, the “object”, is employed to alter the electrical signal to the area of the electroluminescent device to a level sufficient to change light emission. Methods are disclosed to relate the light intensity thus produced to a property of the object thereby allowing a measurement of the property. The method may optionally use one or more additional circuit components.

Methods of producing luminescence by application of a time-varying electrical signal to an electroluminescent device are disclosed whereby the entire system remains at open circuit. At least one article, substance or material, the “object”, is employed to alter the electrical signal to the area of the electroluminescent device to a level sufficient to change light emission. Methods are disclosed to relate the light intensity thus produced to a property of the object thereby allowing a measurement of the property. The method may optionally use one or more additional circuit components.

Embodiments of the invention provide systems and methods for tracking the thermal age of a self-regulating heating cable. Over a time period, current and voltage data for a cable signal are collected, from which spectral information is extracted. The spectral information has a frequency component and an amplitude component. The cable signal is processed to extract a line frequency signature that includes the electrical system's line current frequency and at least some of its harmonics. A ratio of the amplitudes of at least two of the odd harmonics of the line current frequency is calculated. The ratio is compared to an aging curve indicating the thermal age of the cable as a function of the odd-harmonic ratios. The curve may be obtained in a laboratory setting or in the field by characterizing a cable with zero hours of use. The characterizing may include aging the cable to determine the curve.

Embodiments of the invention provide systems and methods for tracking the thermal age of a self-regulating heating cable. Over a time period, current and voltage data for a cable signal are collected, from which spectral information is extracted. The spectral information has a frequency component and an amplitude component. The cable signal is processed to extract a line frequency signature that includes the electrical system's line current frequency and at least some of its harmonics. A ratio of the amplitudes of at least two of the odd harmonics of the line current frequency is calculated. The ratio is compared to an aging curve indicating the thermal age of the cable as a function of the odd-harmonic ratios. The curve may be obtained in a laboratory setting or in the field by characterizing a cable with zero hours of use. The characterizing may include aging the cable to determine the curve.

A chemical sensor may include an electrode array for electrically interfacing with a fluid sample. The sensor can apply an electrical potential to the sample in order to effect a current flow within the sample. The sensor can measure the resulting current through the sample and determine characteristics about the fluid sample from the current measurement. In one mode of operation of the sensor, the applied electrical potential can be controlled to cause desired electrochemical reactions, such as oxidation or reduction, to occur within the sample to determine the concentration of the oxidized or reduced sample constituent. In another mode of operation, the applied electrical potential causes a current to flow simply due to the conductivity of the sample. In various embodiments, the sensor comprises a controller and a switch for switching between various modes of operation and applying appropriate electric potentials to the sample.

A chemical sensor may include an electrode array for electrically interfacing with a fluid sample. The sensor can apply an electrical potential to the sample in order to effect a current flow within the sample. The sensor can measure the resulting current through the sample and determine characteristics about the fluid sample from the current measurement. In one mode of operation of the sensor, the applied electrical potential can be controlled to cause desired electrochemical reactions, such as oxidation or reduction, to occur within the sample to determine the concentration of the oxidized or reduced sample constituent. In another mode of operation, the applied electrical potential causes a current to flow simply due to the conductivity of the sample. In various embodiments, the sensor comprises a controller and a switch for switching between various modes of operation and applying appropriate electric potentials to the sample.