Small Transducer Research Articles

Electromechanical impedance (EMI) technique as alternative to monitor workpiece surface damages after the grinding operation

Electromechanical impedance (EMI) technique has been employed in detection of structural failure in civil and mechanical structures because of its non-destructive property and easy implementation of small and inexpensive piezoelectric transducers that are attached to the structures, which lead to cost reduction as well as lesser dependence of manual inspection methods. In this technique, the capsule is excited by applying a sinusoidal voltage to generate waves to propagate throughout the structure. From the impedance signature of the structure without any damage, any structural change can be detected by measuring the electrical impedance of the piezoelectric (PZT) patch. Based on its real potentiality and because of its non-destructive characteristics, this work aimed to employ the EMI technique as the first alternative to monitor workpiece surface damages after grinding operation with a conventional abrasive grinding wheel. EMI measurements were performed by using a low-cost PZT transducer and under controlled environmental conditions. Microhardness and surface roughness of the machined surfaces, as well as grinding power, were also measured to detect any damage in the machined surface and to stablish relationship with the EMI technique. From the damage indices root mean square deviation (RMSD) and correlation coefficient deviation metric (CCDM), surface alterations on the ground surfaces were inferred by the EMI method. Also, it was observed a good correlation between the EMI technique and the other output parameters that were investigated in this work, such as surface roughness and power grinding, thereby posing as a non-destructive, low-cost, and viable technique to monitor workpiece surface damages in the grinding operation.

Preliminary acousto-ultrasonic investigation for multi-parameter transducer self-diagnostic system in composites

Commercial aerospace vehicles are demanded to withstand harsh conditions with a low weight impact. Composites are massively used to achieve the optimal trade-off about such performances. However, actually the effect of barely visible flaws on the damage tolerance approach reduces strongly the benefits introduced. Structural Health Monitoring is the most promising technology aimed to compensate such shortcoming aspect. Among several methods, guided waves are efficiently adopted to detect hidden flaws using small integrated transducers, whose reliability is affect by hazard operating conditions. The self-sensing of such devices became indeed crucial to reduce false alarms in damage detection. Although the electromechanical impedance technique is proved to be effective for sensor fault due to different degradation levels, several failures may induce different effects warning a possible compensation. The present work discusses such effects with a comprehensive acousto-ultrasonic experimental campaign. The combined wave propagation and electromechanical impedance investigation mostly assesses the necessity and the feasibility of a multi-parametric self-sensing system. This approach is verified performing several measurements using Laser Doppler Velocimetry (LDV) as well as electromechanical signature measurements on typical aeronautical composites.

Adhesive debonding inspection with a small EMAT in resonant mode

In this paper, a noncontact ultrasonic testing method with using a small electromagnetic acoustic transducer (EMAT) in resonant mode is proposed for metal-based adhesive debonding inspection. The small EMAT with a new magnet configuration and a small coil is developed firstly to improve the spatial resolution and detecting ability for minute defects. Different from conventional pulse echo method using short pulse excitation for debonding inspection, a new method based on power spectrum estimation of the resonant ultrasonic signal with long burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting ability of the small EMAT. Finally, ultrasonic C-scan images of specimens with various adhesive bonding are obtained to demonstrate the capability of this technique.

Phased array ultrasonic testing (PAUT) performed on electroslag weld specimen subject to cyclical tension load testing

Following the discovery of discontinuities in a weld specimen, which was made with a process called narrow gap electroslag welding (ESW-NG), the specimen was subject to mechanical cyclical tension loading until failure. The loading involved one block of 100 tension-only cycles at 42 ksi peak stress followed by a second block of 20 tension-only cycles at 55 ksi stress. Phased Array Ultrasonic Testing (PAUT) was performed to understand whether or not the loading protocol has caused the internal discontinuities to increase in length. The PAUT was performed before cycling began and after the end of first block of cycles. Conventional Ultrasonic Testing was also performed in order to develop comparative baseline results. PAUT utilizes an aperture, which is composed of multiple individual small transducer elements which can be pulsed individually at a computer-calculated timing (“phased or delay laws”) producing a sound beam which is swept through a volume of material. Utilizing PAUT, the operator has the ability to “steer” and “focus” the beam electronically through the material being examined at multiple angles in one scan (for example 45° through 75°) in lieu of being fixed at a certain angle as in conventional Ultrasonic testing (UT). The PAUT equipment utilized has the capabilities of 16 active pulsars capable of multiplexing over 64 channels (16:64) displayed in A, B, C, S, Linear scans, or a combination thereof. Scanning with a digital encoder was utilized in order to collect the data for post processing, analysis and data documentation. This presentation will discuss the findings of the PAUT on this weld specimen. The PAUT aperture utilized was a 5L-60 with 1 mm pitch and Sectorial and Linear scans were utilized. The sectorial scan results of the PAUT before and after cycling showed an increase in dimensions of the recorded indications by an average of 6–8 mm or approximately 50% of the original dimensions. The presentation will also include a discussion of the advantages and limitations of PAUT for various bridge applications. The advantages of PAUT include speed, flexibility, and the ability to perform complex inspections.

Transluminal Approach with Bubble-Seeded Histotripsy for Cancer Treatment with Ultrasonic Mechanical Effects

Bubble-seeded histotripsy (BSH) is a newly developed ultrasound-based mechanical fractionation technique using locally injected phase change nanodroplets (PCNDs) as sensitizers. The PCNDs are a kind of microbubble precursor compressed into submicron-size in droplets form, which were designed for local administration and will expand into microbubbles under ultrasound exposure. Previously, we reported that a combination of PCNDs injection and pulsed high-intensity focused ultrasound (pHIFU) with an acoustic intensity as low as about 3 kW/cm2 at 1.1 MHz, which is similar to the acoustic intensity of currently available HIFU coagulation therapy, was enough to induce tissue fractionation after significant antitumor effects in an in vivo study. Toward therapeutic application of BSH to deep-seated tissues such as the pancreas, the transluminal approach, using endoscopic ultrasound was thought to be ideal. Therefore, for a preliminary examination, we developed a new transducer with a small aperture (20- × 20-mm square) and long focal length (35 mm), operating at 2.1 MHz that could be attached to an EUS-mimicking probe. With the newly developed transducer and locally injected PCNDs, predictable tissue mechanical fractionation was observed in both ex vivo and in vivo studies at acoustic intensities that were too low to induce any significant bioeffects (around 4 kW/cm2) without using PCNDs. For in situ monitoring of the treatment site during a procedure, the degree of attenuation of microbubble motions after exposing the microbubbles to pHIFU was monitored, using ultrafast echographic imaging. Microbubble movements were observed to be largest at 25–30 s after pHIFU exposure. On the contrary, after 40 s, the movement of microbubbles decreased to the same level as at the start of the procedure, suggesting that an overdose of pHIFU exposure causes coagulation attributable to the thermal effect caused by absorption of the energy. Those results were promising for expanding the application of BSH for a transluminal approach, using a small transducer under real-time monitoring.

Electret-based microgenerators under sinusoidal excitations: an analytical modeling

The fast-growing number of mobile and wearable applications has driven several innovations in small-scale electret-based energy harvesting due to the compatibility with standard microfabrication processes and the ability to generate electrical energy from ambient vibrations. However, the current modeling methods used to design these small scale transducers or microgenerators are applicable only for constant-speed rotations and small sinusoidal translations, while in practice, large amplitude sinusoidal vibrations can happen. Therefore, in this paper, we formulate an analytical model for electret-based microgenerators under general sinusoidal excitations. The proposed model is validated using finite element modeling combined with numerical simulation approaches presented in the literature. The new model demonstrates a good agreement in estimating both the output voltage and power of the microgenerator. This new model provides useful insights into the microgenerator operating mechanism and design trade-offs, and therefore, can be utilized in the design and performance optimization of these small structures.

Quantitative imaging performance of frequency-tunable capacitive micromachined ultrasonic transducer array designed for intracardiac application: Phantom study

Commercially available intracardiac echo (ICE) catheters face a trade-off between viewing depth and resolution. Frequency-tunable ICE probes would offer versatility of choice between penetration or resolution imaging within a single device. In this phantom study, the imaging performance of a novel, frequency-tunable, 32-element, 1-D CMUT array integrated with front-end electronics is evaluated. Phased-array ultrasound imaging with a forward-looking CMUT probe prototype operated beyond collapse mode at voltages up to three times higher than the collapse voltage (-65 V) is demonstrated. Imaging performance as a function of bias voltage (-70 V to -160 V), transmit pulse frequency (5–25 MHz), and number of transmit pulse cycles (1–3) is quantified, based on which penetration, resolution, and generic imaging modes are identified. It is shown that by utilizing the concept of frequency tuning, images with different characteristics can be generated trading-off the resolution and penetration depth. The penetration mode provides imaging up to 71 mm in the tissue-mimicking phantom, axial resolution of 0.44 mm, and lateral resolution of 0.12 rad. In the resolution mode, axial resolution of 0.055 mm, lateral resolution of 0.035 rad, and penetration depth of 16 mm are measured. These results show what this CMUT array has the potential versatile characteristics needed for intracardiac imaging, despite its relatively small transducer aperture size of 2 mm × 2 mm imposed by the clinical application.

Investigation of a small force standard with the mass based method

<p class="Abstract"><span lang="EN-US">A small force standard with the mass based method </span><span lang="EN-US">i</span><span lang="EN-US">s developed. It is composed of an electromagnetic compensation balance, a nano-positioning stage and a displacement and pitch angle adjustment unit. The small force standard is used to measure spring constant</span><span lang="EN-US">s</span><span lang="EN-US"> of cantilevers in Atomic Force Microscope (AFM) and forces of small force transducers in related applications. Since the balance and the nano-positioning stage are traced to mass and length standards, respectively, the small force standard is SI traceable. The principle and structure of the small force standard and its main components are discussed in detail. The spring constants of several cantilevers used in AFM were calibrated by the small force standard. The calibration results are demonstrated and uncertainties are evaluated. For verifying metrological characteristics of the small force standard, a preliminary international comparison between NIM, PTB and KRISS was carried out. The comparison results </span><span lang="EN-US">wer</span><span lang="EN-US">e in good agreement and indicate that the calibration capabilities of the participating small force standards </span><span lang="EN-US">wer</span><span lang="EN-US">e equivalent within their reported uncertainties.</span></p>

Non-invasive transmission of sensorimotor information in humans using an EEG/focused ultrasound brain-to-brain interface.

We present non-invasive means that detect unilateral hand motor brain activity from one individual and subsequently stimulate the somatosensory area of another individual, thus, enabling the remote hemispheric link between each brain hemisphere in humans. Healthy participants were paired as a sender and a receiver. A sender performed a motor imagery task of either right or left hand, and associated changes in the electroencephalogram (EEG) mu rhythm (8–10 Hz) originating from either hemisphere were programmed to move a computer cursor to a target that appeared in either left or right of the computer screen. When the cursor reaches its target, the outcome was transmitted to another computer over the internet, and actuated the focused ultrasound (FUS) devices that selectively and non-invasively stimulated either the right or left hand somatosensory area of the receiver. Small FUS transducers effectively allowed for the independent administration of stimulatory ultrasonic waves to somatosensory areas. The stimulation elicited unilateral tactile sensation of the hand from the receiver, thus establishing the hemispheric brain-to-brain interface (BBI). Although there was a degree of variability in task accuracy, six pairs of volunteers performed the BBI task in high accuracy, transferring approximately eight commands per minute. Linkage between the hemispheric brain activities among individuals suggests the possibility for expansion of the information bandwidth in the context of BBI.

A New Measurement Approach for Small Deformations of Soil Specimens Using Fiber Bragg Grating Sensors.

A measurement approach for small deformations of soil specimens has been proposed in this study. The proposed approach consists of a small deformation transducer (SDT) based on fiber Bragg grating sensors which could provide an alternative tool to measure local small deformations of a soil specimen with high accuracy. The working principle, design procedures, calibrations and applications of the SDT are presented. An analytical solution is derived to obtain the relationship between the small deformation of the transducer and the wavelength shift of the FBG sensor, which was further evident in the laboratory calibration tests. The measurement range and resolution of the SDT can be adjusted by choosing different length and thickness of the material. The SDT can achieve a strain resolution of 4.45 micro-strains for a soil specimen with 80 mm in height. Measurement errors and stability were also examined and the results show that the maximum measurement error was around 0.01 mm. The designed SDT was further installed in a modified triaxial apparatus. Three shearing tests under different confining pressures were conducted. Results measured by the newly developed SDT are analyzed with comparisons to the results using external linear variable differential transformer (LVDT) transducers. The results provide evidence that this measurement approach is suitable for measuring the local deformations of soil specimens with high accuracy and stability.

A case study in model-based dynamic calibration of small strain gauge force transducers

<p class="Abstract">Investigations of the model-based dynamic calibration of a small strain gauge force transducer of high bandwidth revealed new challenges for parameter identification. This paper discusses a more generalized mechanical model of the calibration set-up employed taking account of the transducer’s connection to its mechanical environment at both ends. Based on new experimental sine and shock force data, the improved model is studied and its parameters are identified. It is shown that the proposed model is capable of linking the calibration results of both calibration methods to a much better degree. This paper is an extended version of the original contribution to the IMEKO 2015 conference in Prague, Czech Republic.</p>

Experimental Demonstration and Circuitry for a Very Compact Coil-Only Pulse Echo EMAT.

This experimental study demonstrates for the first time a solid-state circuitry and design for a simple compact copper coil (without an additional bulky permanent magnet or bulky electromagnet) as a contactless electromagnetic acoustic transducer (EMAT) for pulse echo operation at MHz frequencies. A pulsed ultrasound emission into a metallic test object is electromagnetically excited by an intense MHz burst at up to 500 A through the 0.15 mm filaments of the transducer. Immediately thereafter, a smoother and quasi “DC-like” current of 100 A is applied for about 1 ms and allows an echo detection. The ultrasonic pulse echo operation for a simple, compact, non-contacting copper coil is new. Application scenarios for compact transducer techniques include very narrow and hostile environments, in which, e.g., quickly moving metal parts must be tested with only one, non-contacting ultrasound shot. The small transducer coil can be operated remotely with a cable connection, separate from the much bulkier supply circuitry. Several options for more technical and fundamental progress are discussed.

P002 Abnormal surround inhibition of finger tapping task and cerebellar hyper-activation of functional MRI in patients with focal hand dystonia

Introduction Surround inhibition is one physiological mechanism to select neuronal responses and to focus neural activity in the central nervous system. Within the motor system, it is a mechanism by which basal ganglia circuits selectively execute desired motor programs. Clinical features of focal hand dystonia (FHD) are task specific abnormal posturing due to sustained muscle contractions interfering with the performance of the skilled motor tasks. In dystonic patients, abnormal involuntary co-contraction of the hand muscles is associated with a disruption of SI. Objectives The aim of the study is to research the relationship with disrupted SI and function of central nervous system during motor performance using functional MRI. Patients & methods Seven healthy subjects (mean ages 34.7 ± 9.1 years, all men) and seven patients with writer cramp (mean ages 53.7 ± 17 years, 4 men and 2 women) were enrolled. Surrounding inhibition study: the experiment of surround inhibition was done according to Beck and Hallett. The EMG were recorded in both right first dorsal interosseus muscle (FDI) and abductor polices brevis muscle (APB). SI was evaluated as the ratio of MEP size of APB to that of FDI. Their right hand put on a side-table with their index finger on small tip of force transducer. Subjects pushed down on a small force transducer using their index finger as quickly as possible after an acoustic start signal. MEPs were measured by using single TMS which was given before signal and 100 ms, 150 ms and 1200 ms after signal. The time course of SI was constructed. And also cortical silent periods were measured for the evaluation of cortical inhibition during finger movement. Functional magnetic imaging for task and testing procedures: Subject was required to tap the second finger with the thumb at the speed of about 1 Hz for ten seconds of one session. Each subject participated in two sessions during they performed right-hand tapping or left-hand tapping. Functional MRI contrast analysis of activity was collected during tapping versus rest block. Blood oxygen level-dependent (BOLD) images were recorded. All imaging data were analyzed using analysis of SPM2 software in. Activation area was imaged by statistically activation of BOLD. For functional MRI, epoch-related fMRI design to map regional changes in BOLD signal under the condition of grip task and finger tapping task. Results In normal subjects, significant SI (smaller MEP of APB to FDI) was found within 150 ms after finger tapping. However, FHD showed no SI during finger tapping. In FHD, BOLD activity of contralateral SMA and cerebellum and excessive activation in PMA were observed in four of 7 patients. Hyperactive area around SMA in FHD extended broader than normal subjects. And also hyperactive areas were observed in ipsilateral SMA. Finger tapping task than grip task produced stronger activation in cerebellum and SMA in FHD. Discussion: In normal subjects, significant SI was found within 150 ms during pinching task with 10% Fmax. However, FHD showed no SI during pinching task. In FHD, the finding of fMRI showed BOLD hyper-activation of SMA and excessive activation in PMA. And also hyperactivity is observed in both cerebellar hemispheres. Tapping task than grip task produced hyperactivity in SMA and cerebellum. These findings suggest that skilled task must make less surround inhibition in central nervous system network. The finding of hyperactive BOLD signal suggests that dis-inhibition of central nervous system network. There may be any relationship with a disrupted SI and hyper-activation of cerebellum in fMRI during voluntary movement. Conclusion Our findings showed FHD with disrupted SI had cerebellar hyper activation of cerebellum in fMRI during voluntary movement.

The Usefulness of Intraoperative Transoral Ultrasound Examination for Head and Neck Surgery

Recently, the treatment for early head and neck cancer trends toward a transoral surgery. However, it is difficult to determine the indication for transoral surgery or to evaluate the depth of tumor invasion. Ultrasound (US) examination has some advantages that it can evaluate the tumor in real time and in particular. In this study, we used ultrasonography with small transducer in transoral surgery, and performed intraoral evaluation of tumor thickness. The subjects were patients with oropharyngeal or hypopharyngeal cancer who underwent intraoperative transoral US examination at our department form April 2016 to March 2017. We used Hitachi ARIETTA 70 ultrasound system with laparoscopic US transducer L43K (Hitachi Aloka Medical, Ltd. Tokyo, Japan). We aimed to verify assessable thickness of primary site by transoral US examination and if the tumor was resected with negative deep margin. Furthermore we compared the tumor thickness measured by US and pathological tumor thickness. In total, 10 patients (oropharyngeal cancer: 4, hypopharyngeal cancer: 4, oral cancer: 2) were analyzed, consisting with one patient of Tis, 5 of T1 and 4 of T2. Seven of 10 patients were detectable by US. In unassessable three patients, two cases (Tis and early T1) were too thin to detect by US and one was difficult to evaluate due to the location of the tumor. The minimum thickness of tumor in detectable patients was 2.5 millimeters. In all assessable patients, deep resection margin was negative. The range of tumor thickness measured by US was 2.5 to 18.0 millimeters, and the range of pathological tumor thickness was 1.8 to 9.0 millimeters. Primary site over 2.5 millimeters thickness was detectable by transoral US examination, and was resectable with negative deep margin. Thus, transoral US examination for head and neck cancer was useful to decide deep resection margin in transoral surgery.

Investigation of Silicon Nitride as an Excellent Membrane Material for MEMS Ultrasonic Transducers

Silicon micromachining techniques developed over the last few decades’ aid in precise control over nanometer scale structures. Using these techniques to fabricate transducer elements with small electrode spacing efficient and broadband ultrasonic air transducers can be made. In this paper frequency response profile of a circular capacitive micromachined ultrasonic transducer (CMUT) element with silicon nitride as the membrane material is analytically modelled and compared with FEM simulation results. It is observed that the resonance frequency is highly dependent on the membrane material and structural properties. Silicon nitride serves as an excellent material for generation and detection of ultrasonic waves in air. The results are compared with published experimental values and appreciable agreement is obtained.

Evaluation of a small flat rectangular therapeutic ultrasonic transducer intended for intravascular use

BackgroundThe aim of the proposed study was to evaluate the performance of a flat rectangular (2×10mm2) transducer operating at 4MHz. The intended application of this transducer is intravascular treatment of thrombosis and atherosclerosis. MethodsThe transducer’s thermal capabilities were tested in two different gel phantoms. MR thermometry was used to demonstrate the thermal capabilities of this type of transducer. ResultsTemperature measurements demonstrated that this simple and small transducer adequately produced high temperatures, which can be utilized for therapeutic purposes. These high temperatures were confirmed using thermocouple and MR measurements. Pulsed ultrasound in combination with thrombolytic drugs and microbubbles was utilized to eliminate porcine thrombi. ConclusionsThe proposed transducer has the potentials to treat atherosclerotic lesions using the thermal properties of ultrasound, since high temperatures can be achieved in less than 5s. The results revealed that the destruction of thrombi using pulsed ultrasound requires long exposure time and high microbubble dosage.

Hybrid MRI-Ultrasound acquisitions, and scannerless real-time imaging.

To combine MRI, ultrasound, and computer science methodologies toward generating MRI contrast at the high frame rates of ultrasound, inside and even outside the MRI bore. A small transducer, held onto the abdomen with an adhesive bandage, collected ultrasound signals during MRI. Based on these ultrasound signals and their correlations with MRI, a machine-learning algorithm created synthetic MR images at frame rates up to 100 per second. In one particular implementation, volunteers were taken out of the MRI bore with the ultrasound sensor still in place, and MR images were generated on the basis of ultrasound signal and learned correlations alone in a "scannerless" manner. Hybrid ultrasound-MRI data were acquired in eight separate imaging sessions. Locations of liver features, in synthetic images, were compared with those from acquired images: The mean error was 1.0 pixel (2.1 mm), with best case 0.4 and worst case 4.1 pixels (in the presence of heavy coughing). For results from outside the bore, qualitative validation involved optically tracked ultrasound imaging with/without coughing. The proposed setup can generate an accurate stream of high-speed MR images, up to 100 frames per second, inside or even outside the MR bore. Magn Reson Med 78:897-908, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

All-in one small modular transducer system for ultrasound therapy

We developed new concept all-in one small modular transducer system for ultrasound therapy. Focus position control of HIFU (High Intensity Focused Ultrasound) with multi-elements phase delay control is very popular in clinical application. However, multi-elements driving amplifiers are very large size like a large refrigerator. So, we adopted a direct drive amplifier system for the multi-elements modular transducer. The modular system has some advantages compared to conventional systems. It can be reduced the energy loss of the connecting cable between the transducer element and the amplifier. Other advantages are below. Free placement of module transducer elements like a patient specific body line. Easy maintenance of each element. Easy design change to reduce the manufacturing time. The modular transducer system is composed of four blocks. The first module is multi-channel transducer elements. The second module is multi-channel direct drive amplifier system. The third module is a name-card size multi-channel phase delay signal generator with the phase delay signal set memory bank. The fourth module is a phase delay signal set generating software with a personal computer. It can transmit the signal set to the third module. We manufactured the prototype very small all-in one modular transducer system for ultrasound therapy.

Applying Small Molecule Signal Transducer and Activator of Transcription-3 (STAT3) Protein Inhibitors as Pancreatic Cancer Therapeutics.

Constitutively activated STAT3 protein has been found to be a key regulator of pancreatic cancer and a target for molecular therapeutic intervention. In this study, PG-S3-001, a small molecule derived from the SH-4-54 class of STAT3 inhibitors, was found to inhibit patient-derived pancreatic cancer cell proliferation in vitro and in vivo in the low micromolar range. PG-S3-001 binds the STAT3 protein potently, Kd = 324 nmol/L by surface plasmon resonance, and showed no effect in a kinome screen (>100 cancer-relevant kinases). In vitro studies demonstrated potent cell killing as well as inhibition of STAT3 activation in pancreatic cancer cells. To better model the tumor and its microenvironment, we utilized three-dimensional (3D) cultures of patient-derived pancreatic cancer cells in the absence and presence of cancer-associated fibroblasts (CAF). In this coculture model, inhibition of tumor growth is maintained following STAT3 inhibition in the presence of CAFs. Confocal microscopy was used to verify tumor cell death following treatment of 3D cocultures with PG-S3-001. The 3D model was predictive of in vivo efficacy as significant tumor growth inhibition was observed upon administration of PG-S3-001. These studies showed that the inhibition of STAT3 was able to impact the survival of tumor cells in a relevant 3D model, as well as in a xenograft model using patient-derived cells. Mol Cancer Ther; 15(5); 794-805. ©2016 AACR.

A novel optical telemetry system applied to flowmeter networks

Recently developed transducers utilise the unique characteristics of Deformed Helix Ferroelectric Liquid Crystal (DHFLC) to linearly and passively transduce small voltage signals into the optical domain. These small optical transducers can be retrofitted to an existing flowmeter network where the true benefits of distributed sensing in the optical domain can be leveraged. Signals from multiple sensors can be multiplexed into a single optical fibre for measurement at a remote location. We demonstrate two methods of signal measurement based on a positive displacement oval gear flowmeter. Utilising a reed switch to produce short pulses, errorless flow rate transduction is possible across all flow rates including very low flows. Using a variable reluctance sensor, completely passive transduction of flow rates can be achieved. The same technique can be applied to any sensing network with an electrical signal output.