Sensor interface circuits

Grassi, M., Malcovati, P. and Baschirotto, A. (2007) A 141-dB Dynamic Range CMOS Gas-Sensor Interface Circuit Without Calibration With 16-Bit Digital Output Word. IEEE Journal of Solid-State Circuits, 42,1543-1554. 

Err" signal errors are automatically shown on the LED display in the case of a defective pH electrode or faulty temperature sensor (Pt 100) and for incorrect buffer two set points can be set over any part of the pH, mV or 0° C scale, which when exceeded starts an alarm and/or allows readjustment of dosing valves or pumps via an interface circuit. 

Most microhotplate-based chemical sensors have been realized as multi-chip solutions with separate transducer and electronics chips. One example includes a gas sensor based on a thin metal film [16]. Another example is a hybrid sensor system comprising a tin-oxide-coated microhotplate, an alcohol sensor, a humidity sensor and a corresponding ASIC chip (Application Specific Integrated Circuit) [17]. More recent developments include an interface-circuit chip for metal oxide gas sensors and the conccept for an on-chip driving circuitry architecture of a gas sensor array [18,19]. 

This chapter includes two different sensor system architectures for monolithic gas sensing systems. Section 5.1 describes a mixed-signal architecture. This is an improved version of the first analog implementation [81,91], which was used to develop a first sensor array (see Sect. 6.1). Based on the experience with these analog devices, a complete sensor system with advanced control, readout and interface circuit was devised. This system includes the circular microhotplate that has been described and characterized in Sect. 4.1. Additionally to the fabrication process, a prototype packaging concept was developed that will be presented in Sect. 5.1.6. A microhotplate with a Pt-temperature sensor requires a different system architecture as will be described in Sect. 5.2. A fully differential analog architecture will be presented, which enables operating temperatures up to 500 °C. 

P.F. Ruedi, P. Heim, A. Mortara, E. Franzi, H. Oguey, and X. Arreguit. Interface circuit for metal-oxide gas sensor Digest IEEE Custom Integrated Circuits Conference (2001), 109-112. 

S.A. Bota, A. Dieguez, J.L. Merino, R. Casanova, J. Samitier, and C. Cane. A Monolithic Interface Circuit for Gas Sensor Arrays Control and Measurement , Analog Integrated Circuits and Signal Processing 40 (2004), 175-184. 

Jersch J, Maletzky T, Fuchs H (2006) Interface circuits for quartz crystal sensors in scanning probe microscopy applications. Rev Sci Instrum 77 083701... 

In the use of a QCM as a sensor, oscillator circuits are the most common electrical interface. A frequency counter can then measure the frequency output from the oscillator, which is identical to the resonant frequency of the quartz crystal. There are two general classifications for the oscillator circuits operation in series resonance and operation in parallel resonance. The performance of these circuits and the choice of the proper circuit are discussed extensively elsewhere. 

Most capacitive evaluation circuits do not achieve the maximum possible resolution but are limited by the electromechanical interface, shortcomings in the electronic circuits, or stray signals coupling into the detector and corrupting the output. Section 6.1.2 below illustrates approaches to maximize the sensitivity of capacitive sensor interfaces, potential error sources, and approaches to minimize them. Electronic circuit options are discussed in Section 6.1.3. 

Abstract Oscillators are the standard interface circuits for quartz crystal resonator sensors. When applying these sensors in gases a large set of circuits is available, which can be adapted to particular applications. In liquid applications viscous damping accompanied by a significant loss in the Q factor of the resonator requires specific solutions. We summarize major design rules and discuss approved solutions. We especially address the series resonance frequency and motional resistance determination and parallel capacitance compensation. We furthermore introduce recent developments in network analysis and impulse excitation technique for more sophisticated applications. Impedance analysis especially allows a more complete characterization of the sensor and can nowadays be... 

The application of oscillator circuits as sensor interface for QCM is the most common method. Since a quartz crystal is a resonant element, stable oscillation can be excited by quite simple circuits. They deliver a frequency analog output signal, which can be easily processed in digital systems. Two oscillation conditions can be formulated assuming approximately linear behavior and not considering the pre-oscillation process ... 

The book is intended to give a state-of-the-art overview of the recent achievements in the area of piezoelectric sensors. The focus lies on TSM resonators, since this class of piezoelectric devices is most frequently used in physical and chemical sensor and biosensor apphcations, and they are largely commercially available. The book is divided into three parts. The first four chapters cover the physical background of piezoelectric devices. While Ralf Lucklum and Frank Eichelbaum discuss different interface circuits to drive a TSM resonator in the first chapter, Diethelm Johannsmann provides a comprehensive picture of how to treat different load situations of the quartz crystal microbalance (QCM) in the second, including rather new development in the area of con-... 

Ralf Lucklum, Frank Eichelbaum Interface Circuits for QCM Sensors. 

As chemo-resistive sensors are based on a change in conductivity at high operating temperatures, so main circuit blocks required for interfacing these sensors are driving circuits for micro-heaters, temperature control units and sensing material interface circuits. 

Sensing material interface circuit, the design of this interfacing circuit is one of the main challenging components of a resistive gas sensor. This is because ... 

Bota, S. A., Dieguez, A., Merino, J. L., Casanova, R., Samitier, J. and Cane, C. (2004) A monolithic interface circuit for gas sensor arrays Control and measurement. Analog Integrated Circuits and Signal Processing, 40,175-184. 

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