Probe-type Sensors Research Articles

Automated multiport flow-through water pumping and sampling system

Flow-through systems are often used in aquarium and aquaculture facilities, laboratories, and aboard research vessels and other mobile systems to collect, analyze, and monitor water properties as they vary across time and location. These systems most often intake water from a single source and deliver it to a suite of flow-through sensors after which waste water either exits the system or is recirculated back to the source. Here we describe a system that is designed to take water from multiple sources via a multiport valve manifold and deliver it to a common sample stream, facilitating analysis by a single suite of flow-through and probe type sensors. Build cost depends on the manifold design and the number of valves, but generally under $9000. The inclusion of a Free Surface Interface Cup (FSIC) allows probe type sensors or sample “sippers” that require unpressurized conditions to be utilized down-stream of the pumping system and manifold. With the exception of the multiport sampling manifold, all components of this system are available off-the-shelf, simplifying construction, service, and maintenance. The operating system code is open source and based on the Arduino platform, enabling users to customize the code to better fit their requirements.

Effects of the rotor obliquity on the cylindrical capacitive sensor

The cylindrical capacitive sensor (CCS) is superior to conventional probe-type sensors in measuring the radial error motion of a rotor accurately since the CCS is immune to geometric errors of the rotor. However, due to the extended axial length of the CCS, the obliquity (or the axial tilt) of the rotor may cause unnecessary measurement error. This paper presents the effects of rotor obliquity on the performance of the CCS. The existing analytical model for the CCS has been extended to incorporate the axial tilt of the rotor, which leads to a new mathematical model for the CCS that can describe the complete three-dimensional motion of the rotor. Based on the new mathematical model, a nonlinear analysis is performed to derive the analytical solution of the measured rotor displacement with the CCS. As a result, it has been revealed how the rotor obliquity causes measurement errors in both eccentricity and phase angle. The analytical results are compared and verified with simulations.

Optimal multi-segment cylindrical capacitive sensor

This paper discusses a multi-segment cylindrical capacitive sensor (CCS)optimized to minimize the effects of geometric errors. Spindle error motion is akey index of performance in rotating machines. The CCS was developed as analternative of probe-type sensors and applied to several rotating machineapplications since the spindle error motion can be measured accurately without asignificant effect of geometric errors. However, research on the CCS has so farfocused on the case of two pairs of sensor units. Therefore, it is necessary toinvestigate the general case or multi-segment CCS for a better rejection ofgeometric errors. This work presents generalization of the previous CCSsystem down to a multi-segment CCS. We first introduce a multi-segmentCCS that consists of equally spaced pairs of sensor units of the sameangular size on the circumference, and derive a mathematical model ofthe measuring process with the multi-segment CCS. Theoretical analysisusing the mathematical model shows that a multi-segment CCS withnpairs of sensor units can remove all harmonic errors except the(2nk − 1)th and(2nk + 1)th(k = 1, 2, 3,...)harmonic errors. In addition, the angular size of the multi-segmentCCS is optimized to minimize the effects of geometric errors througha minimum norm approach. The optimal multi-segment CCS withn pairs ofsensor units has the largest sensor unit size among those which remove the(2n − 1)th harmonic error, which is the lowest harmonic error that cannot be removedwith nsensor unit pairs.

Small optical magnetic-field sensor that uses rare-earth iron garnet films based on the Faraday effect

Highly accurate optical magnetic-field probe sensors that use iron garnet films have been developed. New probe-type sensors were designed with a confocal optical system. A new garnet composition, Bi(0.98)Gd(0.92)La(0.03)Y(1.07)Fe(4.72)Ga(0.28)O(12), was found that shows high temperature stability for a sensitivity of less than 2.0% from -20 to +80 degrees C. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 0.3 to 42 mT. An optical current transformer that uses the proposed sensor has an ac linearity of 1.0% for input current up to nearly 300 A. The sensor realized high performance in actual use.

Small Optical Magnetic Field Sensor Probe Using Rare-Earth Iron Garnet Crystals

We developed highly accurate optical magnetic field sensor probes. New probe-type sensors 5 mm in width were designed, using a confocal optical system with two drum-shaped ball lenses. BiRIG films were prepared by the LPE method. We found a new garnet composition, Bi0.98Gd0.92La0.03Y1.07Fe4.72Ga0.28O12, that showed high temperature stability for sensitivities less than 2.0% from - 20°C to +80°C. The linearity error of the sensor output was obtained within 1.0% for alternating magnetic fields from 5.0 Oe to 450 Oe. We also developed optical current transformers (OCTs), using this sensor and a permalloy magnetic core with a 6 mm air gap. The sensitivity of the new OCTs is about four times higher than that of our previous ones. The OCTs showed high performance in practical use.

Flow-through (bio)chemical sensors—Plenary lecture

The basic features and most salient examples of flow-through chemical and biochemical sensors based on the integration of derivative analytical reactions, separation processes (dialysis, gas diffusion, sorption, liquid–liquid extraction) and detection (optical, electroanalytical, mass, thermal) are presented and discussed, and critically compared with those of probe-type sensors and conventional continuous-flow configurations, where such processes take place sequentially in separate modules.