Sensor Output Signals

In this experiment, you will become familiar with an instrumentation amplifier circuit that is used to amplify weak sensor output signals. 

Fig. 20. Typical flow sensor output signal as function of the flow. (For sensor geometry see figure 19 10 mW dissipation in the heater resistor lmW in the sensor restistors 150 O). The sensor can be used op to 100 pl/min (ethanol)...

For a reversible sensor, sensitivity is defined as the change in sensor output signal obtained for an incremental change in the concentration or mass of the analyte, i.e., the slope of the response-vs-concentration curve. Sensitivity for a reversible AW sensor typically has units of [frequency change]/[concentration change], e.g., Hz/M (M mol/L), Hz/(/ug/L), or even ppm >pm (normalized frequency shift/concentration). For an irreversible sensor, sensitivity is more appropriately defined in terms of frequency change/integrated exposure, e.g., Hz/M-min. 

The sensor output signal should be insensitive to the moisture content... 

The relative multiplicative dispersion arising from the sensor output signal is as follows ... 

The most important and substantial, by the time and volume of work required, are those tests where the determination of main metrological characteristics, at which the evaluation of the influence of various external factors on the sensor s sensitivity is performed, should be done. A aoss-sensitivity test to other gases, impact of the presence of humidity on the sensor output signal test at different temperatures, a vibration test, a thermoshock test, and other tests imitating the extreme working conditions of the sensor will follow afterwards. 

Fig. 7.9.15 Magnetic sensor input signal modulated by the tone wheel rotation (blue line). Switching thresholds for defined switching to prevent unwanted switching (green line). Generated sensor output signal by the comparator circuit (red line)...

Drift The change of sensor output signal independent of the measured property over a period of time (see Fig. Id) ... 

The second block of the circuit is a high accuracy instrumentation operational amplifier that makes both sensors output signals Vout 1, Vout 2 difference. Two potentiometers enable respectively offset and gain adjustment. The DC offset adjustment generates an output signal equal to OV when the system detects the zero in the XY position of the platform. The maximum D(3 voltage adjustment which is proportional to the platform movement is made by means of the gain adjustment. 

The sensor output signal of pulse modality flow sensors is strongly tied to the relationship... 

The sensor output signal of pulse modality flow sensors is strongly tied to the relationship between sensing element temperature and flow rate as well to the relationship between sensing element resistivity and temperature [7]. Further explanation of its functionality is discussed in the next section. In steady state, the input heat transfer is balanced by power dissipation ... 

The device was operated at a constant drain-source current and voltage. The measurement was carried out with a feedback loop by regulating the reference voltage. The sensor output signals in terms of gate voltage shift were measured as a function of the DO concentration by a digital voltmeter. 

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