GENERALIZED MEASURING SYSTEM. Stage 1 : A detector- transducing or sensor-transducer stage Stage 2 : An intermediate stage, which is called the signal conditioning stage Stage 3: A terminating or readout stage. INUPUT IDENTIFICATION.
Stage 1:A detector- transducing or sensor-transducer stage
Stage 2: An intermediate stage, which is called the signal conditioning stage
Stage 3: A terminating or readout stage
The measured does not change or not rapidly change with time. Of course, the non-changed measured is the most easily measured quantity. The meter pointer has no difficulty in eventually reaching a definite indicationINUPUT IDENTIFICATION
The measured varies with time in a continuous manner. For instance, the speed of an automobile, as it starts from rest, and the voltage in utility power lines. Temperature, fluid flow, pressure, stress, and strain are normally behave in analog manner.
Digital quantity is that quantity varies in a stepwise manner between two distinct magnitudes: a high and a low voltage, for instance.
Digital quantities are preferred in measuring systems. Noise problem is reduced or eliminated, data transmission is simpler, and computers are designed to process digital information.
Therefore it may be preferred in some cases to convert analog type input to an equivalent digital signal
Transducer classified as:-
-Mechanical : Bourdon tube
-Hydraulic-pneumatic: Float, propeller
-Optical:Photographic film, photoelectric cell
- Electrical:Resistance, coil, condenser.
The purpose of the second stage is to modify the transduced signal so that it will be suitable for the third stage.
The final stage expresses the measured in comprehensible to one of the human sense or to a controller. The output device may be
Displacement type: moving pointer and scale, moving scale and index, light beam and scale, electron beam and scale (CRO), liquid column
Digital type : Direct alphanumeric readout
-Recorders: Digital printing, inked pin and chart, light beam and photographic film, magnetic recording.
Processors: Various type of computing systems or controlling systemsSECOND or INTERMEDIATE STAGESIGNAL-CONDITIONING STAGE
The piston-cylinder combination constitutes a force-summing apparatus sensing and transducing pressure to force. As a secondary transducer, the spring converts the force to displacement. Finally, the transduced input is transferred without signal conditioning to the scale and index for read outTHIRD OR TERMINATING or FINAL STAGE
Fig. 2.3 Gage for measuring pressure in automobile tires