Metglas–Elgiloy bi-layer, stent cell resonators for wireless monitoring of viscosity and mass loading

Green

J. Microelectromech. Syst.

2014

This paper describes resonant wireless strain sensors fabricated from magnetoelastic alloys. The transduction mechanism is the E effect-the change in stiffness of magnetoelastic materials with applied strain or magnetic field. This is measured as a shift in the resonant frequency and is detected wirelessly using pick-up coils utilizing the magnetoelastic coupling of these materials. The sensors are fabricated from a 28-μm-thick foil of Metglas 2826 MB (Fe 40 Ni 38 Mo 4 B 18 ), a ferromagnetic magnetoelastic alloy, using microelectrodischarge machining. Two sensor types are described-single and differential. The single sensor has an active area of 7 × 2 mm 2 , excluding the anchors. At 23°C, it operates at a resonant frequency of 230.8 kHz and has a sensitivity of 13 × 10 3 ppm/mstrain; the dynamic range is 0.05-1.05 mstrain. The differential sensor includes a strain independent reference resonator of area 2 × 0.5 mm 2 in addition to a sensing element of area 2.5 × 0.5 mm 2 that is divided into two segments. The sensor resonance is at 266.4 kHz and reference resonance is at 492.75 kHz. The differential sensor provides a dynamic range for 0-1.85 mstrain with a sensitivity of 12.5 × 10 3 ppm/mstrain at 23°C. The reference resonator of the differential sensor is used to compensate for the temperature dependence of the Young's modulus of Metglas 2826 MB, which is experimentally estimated to be −524 ppm/°C. For an increment of 35°C, uncompensated sensors exhibit a resonant frequency shift of up to 42% of the dynamic range for the single sensor and 30% of the dynamic range of the differential sensor, underscoring the necessity of temperature compensation. The geometry of both types of sensors can be modified to accommodate a variety of sensitivity and dynamic range requirements.[2013-0330] IndexTerms-Strain measurement, magnetoelasticity, resonant sensing, Metglas, E effect.

Section: A Resonating Elementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Passive Wireless Strain Sensors Using Microfabricated Magnetoelastic Beam Elements

Green

J. Microelectromech. Syst.

2014

“…It can be scaled up for a high throughput by the use of batch-mode μEDM [15]. This machining approach has been previously demonstrated for use in machining of Metglas 2826MB™ [16]. The strain sensor as fabricated by µEDM is shown in Fig.…”

Section: Materials and Fabricationmentioning

confidence: 99%

A passive, wireless strain sensor using a microfabricated magnetoelastic beam element

2013

2013 Ieee Sensors

This paper describes a resonant wireless strain sensor fabricated from a magnetoelastic alloy. The sensor consists of a doubly-clamped suspended structure comprised of a resonant strip and a strain attenuating spring. Strain causes a shift in magnetoelastic resonant frequency in the longitudinal mode of the sensor, which is detected wirelessly using pick-up coils. The sensor is fabricated from a 28 μm thick foil of Metglas™ 2826MB (Fe 40 Ni 38 Mo 4 B 18 ), a ferromagnetic magnetoelastic alloy, using micro-electrodischarge machining (µEDM). The sensor has an active area of 7×2 mm 2 and operates at a resonance frequency of 227.4 kHz. It has a sensitivity of 4300 ppm/mstrain; the dynamic range is 0.2-2.8 mstrain. The sensor geometry can be modified to accommodate differing sensitivity and dynamic range requirements.

“…Magnetoelastic sensors are being explored as well. Sensors measuring mass loading, strain, viscosity, temperature, magnetic field among other physical parameters have been previously reported [4–9]. Many sensors based on magnetoelastic materials use a change in resonant frequencies to determine the measurand.…”

Section: Introductionmentioning

confidence: 99%

Wireless strain measurement with a micromachined magnetoelastic resonator using ringdown frequency locking

Green

ISSS J Micro Smart Syst

2017

Resonant magnetoelastic devices are widely used as anti-theft tags and are also being investigated for a range of sensing applications. The vast majority of magnetoelastic devices are operated at resonance, and rely upon an external interface to wirelessly detect the resonant frequency, and other characteristics. For micromachined devices, this detection method must accommodate diminished signal strength and elevated resonant frequencies. Feedthrough of the interrogating stimulus to the detector also presents a significant challenge. This paper describes a method of interrogating wireless magnetoelastic strain sensors using a new frequency-lock approach. Following a brief excitation pulse, the sensor ring-down is analyzed and a feedback loop is used to match the excitation frequency and the resonant frequency. Data acquisition hardware is used in conjunction with custom software to implement the frequency-lock loop. Advantages of the method include temporal isolation of interrogating stimulus from the sensor response and near real-time tracking of resonant frequencies. The method was investigated using a family of wireless strain sensors with resonant frequencies ranging from 120 to 240 kHz. Strain levels extending to 3.5 mstrain and sensitivities up to 14300 ppm/mstrain were measured with response times faster than 0.5 s. The standard deviation of the locked frequency did not exceed 0.1%.