Sensor output ratio

Figure 4. Theoretical sensor output as a function of the air-fuel ratio...

Sensor sensitivity is the ratio of the change in sensor output to the change in the measurand (slope of the cahbration curve) ... 

Sensor accuracy describes the closeness of agreement between a measured value and a true value of the measurand (concentration of analyte or refractive index). Sensor accuracy is usually expressed in absolute terms or as a percentage of the error/output ratio. 

The sensor element needs to be maintained at 750° C and is heated up by the heater. However, if heater is operated by a constant voltage, the temperature varies by 242° C in the driving region. Conversely, if the heater is controlled by the sensor element resistance constant, the temperature varies only by 46°C. Furthermore, the temperature drops to 100°C at the constant voltage, when the fuel is cut off but hardly varies as constant control of the sensor element resistance. The purpose of the air/fuel ratio control will be achieved with the control to maintain the sensor output accuracy. 

To avoid the uncertainties of temperature measurement associated with the uncertainty of emissivity, a two-color pyrometer is recommended, which analyzes the body radiation properties for two wavelengths. In the two-color or ratio pyrometer the radiation is detected at two separate wavelengths for which emis-sivities of the surface can be considered nearly the same. Thus the ratio of the thermal radiation sensor output calculated for two wavelengths by Wien s law is obtained as... 

If the sensitivity (5 v) of a sensor is defined as the ratio between the changes in the sensor output voltage and flow... 

Figure 6.36 is a schematic of a detection system for the moisture sensor that permits continuous spatial resolution based on time-division multiplexing. The photodetectors, PD also function as wavelength filters. PDl and PDl produce electrical signals that are proportional to the light intensity at 0.67 pm before and after the fiber sensor. The ratio of these outputs is calculated by R1 in order to nulHfy the effects of any... 

If the spectra Zi(cu) and Z2(tu) of the two sensors outputs are contaminated with instrumental noise (a noncausal output), a simple ratio Z2/Z1 may yield a biased or unreliable estimate of the response. By using only the correlated part of the signals, i.e., the part due to the common input of both sensors, the ground noise in this case, a more reliable estimate, will be obtained. This may be done by using a known relation between input and output of linear and causal systems the input-output cross-spectrum is the product of the transfer function and the input power spectrum (see, e.g., Ljung 1999). Consider a linear system whose input is the output of seismometer 1 (Zi) and its output is the output of seismometer 2 (Z2). This system would have a transfer function A2M1 = P2i(oj)/Pii(ffl)>... 

The accuracy of plume gas ratios reported from multi-gas systems depends on a number of factors influencing the sensor measurement error. These include sensor calibration, linearity and possible calibration drift, the sensor baseUne and possible temperature, humidity and pressure dependences of the sensor output, as outlined below. 

Figure 4 shows the theoretical output of a sensor calculated using the Nernst equation and the oxygen partial pressures of Figure 3. Again note the step change at the stoichiometric air-fuel ratio. Many commercially available sensors have outputs that closely approach this theoretical relationship.

Altitude Response. Pressure response is an issue that needs to be addressed for every instrument deployed on an aircraft. First, it must be decided how chemical abundances are to be reported. If standard practice is followed and they are reported as mixing ratios, then it must be determined whether the instrument is fundamentally a mass- or a concentration-depen-dent sensor, because this definition determines the first-order means by which instrument response is converted to mixing ratios as a function of pressure. In this context, a mass-sensitive detector is a device with an output signal that is a function of the mass flow of analyte molecules a concentration-sensitive detector is one in which the response is proportional to the absolute concentration, that is, molecules per cubic centimeter. 

A comparative study of the readout options for the SAW sensor with additional film has shown that for a single SAW sensor the highest signal-to-noise ratio is obtained from the amplitude measurement (Wohltjen and Dessy, 1979). Voltage output related to the phase-shift as discussed above works well for dual delay lines. There are also inherent advantages in measurement of the change of the resonant frequency. The frequency shift due to deposited film of low elastic shear modulus p is... 

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