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51Last Rev.: 25 AUG 08 Sensor Calibration : MIME 3470 Page 1 Grading Sheet ~~~~~~~~~~~~~~ MIME 3470—Thermal Science Laboratory ~~~~~~~~~~~~~~ Laboratory №. X SENSOR CALIBRATION Students’ Names Section № POINTS 10 APPEARANCE, ORGANIZATION, ENGLISH, and GRAMMAR MATHCAD TURBINE-TYPE METER CALIBRATION CURVE PRESSURE TRANSDUCER CALIBRATION CURVE SHEAR BEAM CALIBRATION CURVE 25 25 25 DISCUSSION CONCLUSIONS ORIGINAL DATA SHEET TOTAL Comments d GRADER— 5 5 5 100 SCORE TOTAL 52Last Rev.: 25 AUG 08 Sensor Calibration : MIME 3470 MIME 3470—Thermal Science Laboratory ~~~~~~~~~~~~~~ Laboratory №. X SENSOR CALIBRATION ~~~~~~~~~~~~~~ LAB PARTNERS: NAME NAME NAME SECTION № EXPERIMENT TIME/DATE: NAME NAME NAME TIME, DATE ~~~~~~~~~~~~~~ OBJECTIVE—The objective of this experiment is to familiarize the student with some common types of sensors used in fluid engineering applications. The students will construct calibration curves and determine sensor characteristics. INTRODUCTION—There are many different sensors used in fluid engineering: temperature sensors, pressure sensors, flow meters, and load cells are only a few. The subject of this experiment is to calibrate some of the sensors that will be used in later experiments in this class. 1. The Turbine-type Flow Meter Turbine flow meters are the most popular way to measure flow electronically in a wide range of industries. Inside a turbine meter, the flow medium engages a vaned rotor, causing it to rotate at an angular velocity that is directly proportional to the flow rate. As the turbine rotates, an AC voltage is induced in a magnetic pickup coil mounted outside the fluid process. As each turbine blade passes the base of the pickup coil, the magnetic flux density is affected, inducing a voltage pulse. Schematic of the basic Each pulse represents a distinct operation of the turbinevolume of fluid that has been type flowmeter [1] displaced through two adjacent blades. The pulse rate generated is thus a measure of the flow rate. In theory, this produces a linear relationship between the flow rate and the pulse rate. In reality, friction in the system requires a minimum flow for the linear relationship to be approximately true. Page 2 3. Shear-Beam Load Cell There are many types of load cells for force measurement, with the most common being straingage based. A strain-gage load cell consists of an elastic element with mounted strain gages Depending on range and stiffness requirements, the sensing element can be a compression/tension member, cantilever-beam, and shear-beam, among others. In a shear-beam sensor, the elastic member produces equal tensile and compressive stresses at adjacent locations on the same surface as shown, allowing the use of prefabricated planar gage assemblies that incorporate a full bridge of gages. The gage’s “unit construction” offers many manufacturing and performance advantages. Experimental Procedure: Turbine Meter— The student will be calibrating the turbine meter against a variable-area flow meter (rotameter). The frequency output of the turbine meter will be determined by using a computer-based data acquisition and analysis system to count the number of cycles over a fixed period of time. Measure the frequency output of the meter against the flow rate as indicated by the rotameter. For your report: on one plot, show the measured flow rates against the frequency readings and determine and plot a regressed line of the data. This is a calibration curve. The Mathcad linear regression function is documented below (source Mathcad Help). The slope of the curve indicates the volume per pulse of the turbine meter. 2. Pressure Transducer Check out also the SLOPE and INTERCEPT functions in Mathcad Help Because of the great variety of conditions, ranges, and materials for which pressure must be measured, there are many different types of pressure sensor designs. Often pressure can be converted to some immediate form, such as displacement. The sensor then converts this displacement into an electrical output such as voltage or current. The three most universal types of pressure transducers of this form are the strain gage, variable capacitance, and piezoelectric. Off all the pressure sensors, Wheatstone bridge (strain based) sensors are the most common. All bridge sensors make use of a stain gage and a diaphragm. When a change in pressure causes the diaphragm to deflect, a corresponding change in resistance is induced in the strain gage attached to the diaphragm. This in turn causes a change in the Wheatstone bridge balance and voltage output. Pressure Transducer – The pressure transducer will be calibrated using a handheld electronic pressure calibrator. The voltage output of the transducer will be measured against the input pressure. For your report: on one plot, show the input pressure against the voltage readings and determine and plot a regressed line of this data. This is a calibration curve. The Mathcad linear regression function again will be used. The slope of the curve indicates pressure per voltage output of the transducer. Shear-Beam Load Cell – The student will calibrate the load cell by hanging weights and noting the outputted voltage. For your report: on one plot, show the weights against the voltage readings and determine and plot a regressed line of this data. The slope of the curve indicates force per voltage output of the load cell. Last Rev. 6/28/2017 Ordered Data, Calculations, & Results MATHCAD OBJECT--DOUBLE CLICK TO OPEN Sensor Calibration : MIME 3470 Page 3 Last Rev.: 25 AUG 08 DISCUSSION OF RESULTS Sensor Calibration : MIME 3470 CONCLUSIONS Page 4 Last Rev.: 25 AUG 08 Sensor Calibration : MIME 3470 Page 5 DATA SHEET FOR SENSOR CALIBRATION Time/Date: ___________________ Lab Partners ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ ____________________________ Turbine Meter: Rotameter Flow rate (gpm) Frequency, Hz Pressure, inH20 Voltage, V Weight, g Voltage, V d d d d d d d d Pressure Transducer: d d d d d d d d Load Cell: d d d d d d d d