Abstract: A power-on-reset circuit (POR) for integrated circuits that detects the minimum power levels needed to operate the most critical circuit(s) reliably. The circuit is implemented in a customized POR built into a custom IC, and emulates the critical circuit transistors in the custom IC using mimicking counterparts which are similarly affected by changes in temperature and process variations as the main circuit components. The mimicking counterparts may have smaller dimensions, to draw less current but still emulate the characteristics of the main working circuit components. Each critical sub-circuit of the main circuit may have a mimicking POR, and the multiple PORs may have their outputs combined by logic so that subtle failure modes can be modeled in the POR. The POR allows operation of the main circuit to continue at the lowest possible voltage levels while reducing the risk of unexpected results or undetected non-catastrophic failures.

Abstract: A power-on-reset circuit (POR) for integrated circuits that detects the minimum power levels needed to operate the most critical circuit(s) reliably. The circuit is implemented in a customized POR built into a custom IC, and emulates the critical circuit transistors in the custom IC using mimicking counterparts which are similarly affected by changes in temperature and process variations as the main circuit components. The mimicking counterparts may have smaller dimensions, to draw less current but still emulate the characteristics of the main working circuit components. Each critical sub-circuit of the main circuit may have a mimicking POR, and the multiple PORs may have their outputs combined by logic so that subtle failure modes can be modeled in the POR. The POR allows operation of the main circuit to continue at the lowest possible voltage levels while reducing the risk of unexpected results or undetected non-catastrophic failures.

Abstract: A method for connecting optical signals carried by optical fibers between an optical encoder readhead and an optical signal processing IC having a plurality of photodetector portions arranged in a photodetector configuration. The optical signal processing IC is fixed to a substrate at a first position and orientation. Then, a reference-surface block including at least one reference surface is fixed to the substrate in a second orientation and position based on the first position and orientation. A fiber-optic end piece is provided, which has at least one corresponding-reference surface and a plurality of optical fiber locating features that are arranged relative to the corresponding-reference surface. A plurality of the optical fibers are fixed to the plurality of optical fiber locating features to provide a coupling configuration of optical fiber ends that nominally matches the photodetector configuration.

Abstract: An image comparison method and an interpolation method to determine the image offset corresponding to the extreme value of the comparison contributes to systematic errors in estimating the displacement of the surface from the images. The systematic errors are rejected by correlation-based comparison systems and methods which reduce the curvature of the correlation function for offsets that bound the extreme value, and by interpolation systems and methods that are relatively insensitive to the asymmetry of the correlation function value points selected as the basis for the interpolation. These systems and methods allow fast, highly accurate, displacement determinations using relatively simplified calculations and relatively few correlation function value points.

Abstract: A low voltage low power signal processing system and method for use in low power and/or portable measuring instruments such as linear or rotary encoders, electronic calipers and the like. In one embodiment, the analog-to-digital converter is implemented as a parallel, single ramp, with two matched comparators for each leg of differential input, which can be implemented with relatively simple circuitry, and consequently be of a small size. The system may be used with a three-phase transducer configuration, for which the preferred signal processing techniques are able to cancel most of the third harmonic distortion in the system, and for which the fully differential signal processing methods of the invention are advantageous. The invention may be used in a portable measuring instrument that operates from a single 1.5 volt watch battery or solar cell, and that has a current drain of 5 microamps.

Abstract: A low voltage, low power versatile and compact delay circuit for CMOS integrated circuits. The biasing circuit and comparator of the delay circuit are implemented with a relatively few simple transistor stages. This approach makes the circuit compact and allows for operation at very low supply voltages (e.g., 1.5 volts). The time delay of the delay circuit is made to depend only on passive resistive and capacitive components. The time delay is thus insensitive to fluctuations in the supply voltage, as well as fluctuations in temperature. This configuration is particularly advantageous in circuits where several timing elements need to track with one another, as they can all be formed with resistors and capacitors of the same construction. The design also makes the circuit insensitive to process parameters, as well as later environmental effects due to operating temperature, circuit aging, and the like.

Abstract: A low voltage, low power versatile and compact delay circuit for CMOS integrated circuits. The biasing circuit and comparator of the delay circuit are implemented with a relatively few simple transistor stages. This approach makes the circuit compact and allows for operation at very low supply voltages (e.g., 1.5 volts). The time delay of the delay circuit is made to depend only on passive resistive and capacitive components. The time delay is thus insensitive to fluctuations in the supply voltage, as well as fluctuations in temperature. This configuration is particularly advantageous in circuits where several timing elements need to track with one another, as they can all be formed with resistors and capacitors of the same construction. The design also makes the circuit insensitive to process parameters, as well as later environmental effects due to operating temperature, circuit aging, and the like.

Abstract: A low voltage low power signal processing system and method for use in low power and/or portable measuring instruments such as linear or rotary encoders, electronic calipers and the like. In one embodiment, the analog-to-digital converter is implemented as a parallel, single ramp, with two matched comparators for each leg of differential input, which can be implemented with relatively simple circuitry, and consequently be of a small size. The system may be used with a three-phase transducer configuration, for which the preferred signal processing techniques are able to cancel most of the third harmonic distortion in the system, and for which the fully differential signal processing methods of the invention are advantageous. The invention may be used in a portable measuring instrument that operates from a single 1.5 volt watch battery or solar cell, and that has a current drain of 5 microamps.

Abstract: A system and method for determination of error parameters for performing self-calibration and other functions in a transducer. The method utilizes the minimum and maximum values of the output signals of the transducer. To obtain these values, the output signals are measured at various times according to the sample timing, as the read head is scanned relative to the scale. The offset for each phase is determined to be equal to the average between the maximum and minimum voltages. The signal amplitudes are equal to the difference between the maximum and the minimum voltages, divided by two. By comparing the amplitude for each phase, the amplitude mismatch is found. The phase relation error may be determined by first removing the amplitude mismatch and the offset errors from each phase, and then comparing the relative amplitudes of the two signals at a given point in relation to what they ought to be with no phase relation error.

Abstract: An image which is determined by surface is captured and stored by sensing device. Subsequently, at a second image corresponding to a displacement of the surface is captured and stored. The two images are repeatedly compared at different offsets in a displacement direction. Theoretically, the most extreme value of the comparison will occur at the image offset that corresponds exactly with the actual displacement. However, typically none of the comparison offsets correspond exactly with the actual displacement, therefore interpolation between the comparison offsets is required. The method of comparing the images, as well as the method of interpolating to determining the image offset corresponding to the extreme value of the comparison can both contribute to systematic errors in estimating the displacement of the surface from the images.

Abstract: Power saving methods for a battery powered electronic measurement system includes controlling the clock speed for different subsystems of the electronic measurement system and controlling the timing cycles of a controller of the electronic measurement system. Controlling the clock speed of the different subsystems includes using a controller clock for the controller and an internal clock for a signal generating and processing circuit. The internal clock runs at a high frequency during a measurement operation. During other times, the internal clock is disabled. The controller clock outputs a first clock signal having a slow frequency which is substantially slower than the internal clock signal and a second clock signal having an extremely slow frequency which is substantially slower than the first clock signal.

Abstract: A fast, open-loop amplifier for an electronic measuring system is formed by a folded, differential, open-loop amplifier. This amplifier includes a differential common-source portion, a current mirror portion and a load portion. The current mirror portion is connected between the differential common-source portion and the load portion. The load portion is connected to a common voltage supply portion. The fast, open-loop amplifier can include multiple stages, where each stage includes the folded, differential, open-loop amplifier. In this case, each stage can have its own common voltage supply portion. Alternatively, a single common voltage supply portion can be shared between the stages. All the transistors of the differential common source portion and the load portion have the same type of doping, while all the transistors of the current mirror are the same type of doping, but of a type which is different than that used in the differential common source amplifier portion and the load portion.

Abstract: The fast sampling method for taking a position measurement with an electronic measurement system incorporating a capacitive position transducer of this invention allows such capacitive position transducers to be used in contaminant filled environments, such as on a shop floor or in the outdoors. By sampling the output signals within 25 ns-35 ns from when the input signals were applied to the capacitive position transducer, the adverse effects of resistive contamination can be avoided.

Abstract: A sensor for sensing the level of oil or transmission fluid under both normal and extreme temperature conditions. The only active components of the sensor have input and leakage currents substantially lower than those of diodes and current sources under high temperature conditions. The sensor has a probe, including a pair of electrodes forming a level detecting capacitor, adapted to extend in the vessel to detect the level of the liquid. A reference capacitor is included which has a capacitance substantially the same as the capacitance of the level detecting capacitor when no dielectric liquid is present between the electrodes of the level detecting capacitor. Circuitry is provided for measuring the capacitance of each capacitor and for deriving from the capacitance measurements a signal proportional to the level of the dielectric liquid at the sensor. Circuitry is also provided for testing whether the reference capacitor is operating properly.

Abstract: A rotational displacement sensor includes a pair of coils stationarily mounted adjacent a rotatable cam formed of a metallic material. The coils are energized by high frequency alternating current. A differential amplifier is connected to the coils such that the output of the amplifier is linearly proportional to the rotational angular displacement of the cam relative to the coils.

Abstract: An oil level sensor includes a sensor body adapted to be mounted to the block or casing of an oil-containing reservoir. A probe including a pair of electrodes forming a capacitor extends from the sensor body so that the capacitor will be at least partially immersed in the oil to detect the level thereof. At least one of the electrodes is insulated so that the apparent capacitance of the capacitor is relatively insensitive to any change in the conductivity of the oil at high temperatures. Circuitry is provided in response to the capacitance of the capacitor for signalling the level of the oil, which capacitance is a function of the oil level. The sensor body is mounted to the block by external threads on the probe. The electrodes of the probe extend proximally past the threads to provide an increased capacitance for the sensor. The electrodes of the probe are concentric and the inner electrode is supported at both ends to reduce fatigue.