Sensors lab. User Manual

Transcription

1 Sensors lab User Manual

2 Annotation This document is a user manual for laboratory-based practical on the discipline Measurement of physical quantities and includes: description of the educational laboratory test bench; description of the Software, included in the laboratory kit; study guide on performing laboratory works. 2

3 Table of contents Annotation... 2 Table of contents... 3 Safety precautions Educational laboratory test bench Experimental modules Temperature measurement module Strain-gage measurement module Pressure measurement module Distance and displacement measurement module Vibration measurement module Sound and vibration measurement module NI cdaq measurement system NI cdaq 9178 data acquisition system NI 9474 high-speed sourcing digital output module NI 9205 analog input module NI channel universal C Series module NI 9237 simultaneous bridge module NI 9211 thermocouple input module NI 9401 bidirectional digital input module NI 9263 analog output module NI 9234 dynamic signal acquisition module Connector block and cables Software description Software activation Measurements Working with graphs Ultrasound and its implementation Theory Equipment description Order of performance of the laboratory work «Ultrasound velocity measurement» Checking questions

4 Safety precautions Follow the safety rules when connecting the equipment, during laboratory works and maintenance. It is prohibited to disassemble the power supply units of the workstations NI PXI, NI crio, NI cdaq and the sensors lab test bench, to connect other power supplies to the system and make any external connections. The system power supply must be connected to a grounded socket outlet. It is allowed to use the laboratory bench only for indoor test. It is prohibited to plug in laboratory benches in the presence of highly flammable liquids or in atmosphere that contains combustible gases. Maintenance personnel must be highly qualified. If a problem occurs or the bench gives off a smell, indicating inflammation of electrical elements or wires, work with the bench should be discontinued immediately switching it off and turning to attending personnel. Laboratory bench should be powered up and laboratory works should be performed only in the presence of an instructor. User Manual instructions on measuring units connection diagram on the bench should be strictly followed. Wrong terminal connection may lead to the failure of measuring system and may cause damage to the components. 4

5 1 Educational laboratory test bench Laboratory testbench is used to perform laboratory works on the following courses: «Measurement of physical quantities», «Sensors of technological parameters», «Technological measurements». Pressure measurement module Distance and displacement measurement module Strain-gage measurement module Temperature measurement module Vibration measurement module Sound and vibration measurement module Connector block Fig. 1.1 General view of the laboratory testbench The laboratory testbench is composed as follows: experimental modules; cdaq measuring system; connector block; connector cables. 5

6 1.1 Experimental modules Experimental modules are special devices that allow users to create required physical conditions and measure corresponding physical quantities with the help of sensors of nonelectrical quantities. The system is composed of the following experimental modules: Temperature measurement module; Distance and displacement measurement module; Strain-gage measurement module; Pressure measurement module; Vibration measurement module; Sound and vibration measurement module Temperature measurement module Temperature measurement module consists of a heating element which includes temperature sensors, the terminals of which are located on the front panel of the module. Necessary temperature is maintained in the heating element by using a controlled heater, the terminals of which are located under the heating element on the front panel (Fig ). Fig General view of the temperature measurement module To perform laboratory works, J and K type thermocouples, thermistors with rated resistance of 10 kω and transistor temperature sensor based on bipolar КТ358В transistor are used. The temperature of the heater is measured by using a resistance temperature detector (RTD) or resistance thermometer with static characteristic Pt100. Fig shows the internal structure of the module. 6

7 Fig Module s schematic structure Strain-gage measurement module The strain-gage measurement module (Fig ) is composed as follows: strain-gage sensor, the terminals of which are placed on the module front panel to connect the NI 9237 module; cantilever beam to which is attached a 350 Ω strain gage. Fig General view of the strain-gage measurement module The strain gage, attached to the cantilever beam, is connected to a quarter-bridge measurement circuit. To produce strains of different degrees, two 100 (± 0,5) g weights are placed on the free end of the beam. 7

8 1.1.3 Pressure measurement module Pressure measurement module (Fig ) is composed as follows: metal pressure cylinder connected to the sensors; hand pump for pumping air into the metal cylinder; DM1 and DM2 pressure sensors, connected to the metal cylinder inputs via rubber tubes. Fig General view of the pressure measurement module Pressure measurement module is used to create different air pressures using the hand pump and to measure the created pressures using sensors, integrates into the module. Differential DM1 and DM2 pressure manometers measure gage pressure transmitted from the cylinder via rubber tubes. Absolute M manometer is used to measure atmospheric pressure and, if necessary, total pressure after connecting to it a tube, which transmits pressure from the metal cylinder. Piezo differential pressure sensor with MPX5500DP output voltage signal and measurement range from 0 to 500 kpa is used as differential DM1 and DM2 manometers. Piezo absolute pressure sensor with MPX4250АP output voltage signal and measurement range from 0 to 250 kpa is used as the absolute M manometer. 8

9 1.1.4 Distance and displacement measurement module Distance and displacement measurement module (Fig ) consists of 3 functional parts: distance meter (ultrasonic distance sensor); linear displacement probe (optical linear encoder); moving mechanism based on a stepper motor linear actuator. Fig General view of the distance and displacement measurement module Operating principle of the ultrasonic distance sensor is based on the generating of a 40 khz ultrasonic pulse and measuring the pulse travel time from the source to the object (reflector) and back. Linear displacement probe is an optical linear encoder (it is used to perform precise measurements of a set distance between ultrasonic pulse source and reflector) in a special case for easy connection to the terminals and for adapter circuit. At moving the beam to the left or to the right, pulses are generated at A and B terminals, the number of which defines the amount of movement and the 90 phase shift defines the direction of movement. The moving mechanism consists of a rectangular steel sheet for reflecting the ultrasonic waves, which is rigidly attached to the stepper motor and to the beam of the linear encoder. There is a special case under the stepper motor to simplificate the connections Vibration measurement module Vibration measurement module (Fig ) consists of: vibration source; vibration sensor (acceleration). 9

10 A motor with unbalanced rotating axis installed in a special case is used as a vibration source. The case vibration changes according to the engine rotation frequency, which depends on the set power of the motor electric supply. The latter is controlled by PWM modulation. Vibration sensor (1) is installed on the motor case (2) as shown on the Fig Y X 1 2 Fig Vibration sensor location on the motor case Acceleration in two directions (x and y) is measured by means of the vibration sensor, as which an ADXL203EB accelerometer with signal conditioned voltage outputs is used. Fig General view of the vibration measurement module Sound and vibration measurement module Sound and vibration measurement module is used for sound measurements and study of acoustic signals characteristics under different conditions. Modules front panel (Fig ) contains the following elements: acoustic signals source (1); input of acoustic signals source (AUDIO IN CH0); noise source switch (DISTORTION); inputs of acoustic signal meters (AUDIO OUT CH0, AUDIO OUT CH1); controlled vibration sources (2); 10

11 vibration sources monitoring unit (FAN SPEED CONTROL); vibration source selection switch (BALANCED FAN/UNBALANSED FAN); output of X-direction vibration acceleration meter (X ACCELERATION); output of Y-direction vibration acceleration meter (Y ACCELERATION); tachometer output (TACH OUT); input of 15 V DC power supply (POWER IN 15V DC 0.8 A). 2 1 Fig Sound and vibration measurement module 1.2 NI cdaq measurement system NI cdaq measurement system is composed as follows: NI cdaq 9178 data acquisition system; NI 9474 high-speed sourcing digital output module; NI 9205 analog input module; NI channel universal C Series module; NI 9237 simultaneous bridge module; NI 9211 thermocouple input module; NI 9401 bidirectional digital input module; NI 9263 analog output module; NI 9234 dynamic signal acquisition module. Fig shows the general view of the measurement system. 11

12 Fig General view of NI cdaq measurement system NI cdaq 9178 data acquisition system The NI cdaq-9178 (Fig ) is an 8-slot NI CompactDAQ USB chassis designed for small, portable, mixed-measurement test systems. Combine the cdaq-9178 with up to eight NI C Series I/O modules for a custom analog input, analog output, digital I/O, and counter/timer measurement system. Modules are available for a variety of sensor measurements including thermocouples, RTDs, strain gages, load and pressure transducers, torque cells, accelerometers, flow meters, and microphones. NI CompactDAQ systems combine sensor measurements with voltage, current, and digital signals to create custom, mixed-measurement systems with a single, simple USB cable back to the PC, laptop, or netbook. The cdaq-9178 has four 32-bit general-purpose counter/timers built in. Fig General view of NI cdaq 9178 chassis NI 9474 high-speed sourcing digital output module The NI 9474 is a C Series 8-channel, 1 µs high-speed sourcing digital output module. It works in any NI CompactDAQ or CompactRIO chassis. Each channel is compatible with 5 to 30 V signals and features transient overvoltage protection of 2,300 Vrms between the output channels and earth ground. Each channel also has an LED that indicates the state of that channel. With the NI 9474, you can connect directly to a variety of industrial devices such as motors, actuators, and relays. 12

13 The NI 9474 module is a correlated digital module which means it can perform correlated operations, triggering, and synchronization when installed in an NI CompactDAQ chassis. Fig a) and b) show the general view of the module NI 9474 and its terminals on the connector block accordingly. а) general view of the module NI 9474 b) terminals of NI 9474 on the connector block Fig NI 9205 analog input module The NI 9205 is a C Series module, for use with NI CompactDAQ and CompactRIO chassis. The NI 9205 features 32 single-ended or 16 differential analog inputs, 16-bit resolution, and a maximum sampling rate of 250 ks/s. Each channel has programmable input ranges of ±200 mv, ±1, ±5, and ±10 V. To protect against signal transients, the NI 9205 includes up to 60 V of overvoltage protection between input channels and common (COM). In addition, the NI 9205 also includes a channel-to-earth-ground double isolation barrier for safety, noise immunity, and high common-mode voltage range. It is rated for 1,000 Vrms transient overvoltage protection. There are two connector options for the NI 9205; a 36-position spring terminal connector for direct connectivity or a 37-position D-Sub connector. To add strain relief and high-voltage protection to the 36-position terminal of the NI 9205, NI recommends the NI 9940 strain-relief connector accessory. Fig shows the NI 9205 terminals assignment. 13

14 Fig NI 9205 terminals assignment Fig a) and b) show the general view of the module NI 9205 and its terminals on the connector block accordingly. а) general view of the module NI 9205 b) terminals of NI 9205 on the connector block Fig NI channel universal C Series module The NI 9219 is a 4-channel universal C Series module designed for multipurpose testing in any NI CompactDAQ or CompactRIO chassis. With the NI 9219, you can measure several signals from sensors such as strain gages, RTDs, thermocouples, load cells, and other powered sensors. The channels are individually selectable, so you can perform a different measurement type on each of the four channels. Measurement ranges differ for each type of measurement and include up to ±60 V for voltage and ±25 ma for current. Fig a) and b) show the general view of the module NI 9219 and its terminals on the connector block accordingly. 14

15 а) general view of the module NI 9219 b) terminals of NI 9219 on the connector block Fig NI 9237 simultaneous bridge module The National Instruments 9237 simultaneous bridge module for use with NI CompactDAQ and CompactRIO contains all the signal conditioning required to power and measure up to four bridge-based sensors simultaneously. The high sampling rate and bandwidth of the NI 9237 offer a high-quality, high-speed strain or load measurement system with zero interchannel phase delay. With 60 VDC isolation and 1,000 Vrms transient isolation, the NI 9237 has high common-mode noise rejection and increased safety for both the operator and test system. Fig a) and b) show the general view of the module NI 9237 and its terminals on the connector block accordingly. а) general view of the module NI 9237 b) terminals of NI 9237 on the connector block Fig

16 1.2.6 NI 9211 thermocouple input module The NI 9211 thermocouple input module for use with NI CompactDAQ and CompactRIO chassis includes a 24-bit delta-sigma ADC, antialiasing filters, open-thermocouple detection, and cold-junction compensation for high-accuracy thermocouple measurements. The NI 9211 contains NIST-traceable calibration and channel-to-earth ground double isolation barrier for safety, noise immunity, and high common-mode voltage range. Fig a) and b) show the general view of the module NI 9211 and its terminals on the connector block accordingly. а) general view of the module NI 9211 b) terminals of NI 9211 on the connector block Fig NI 9401 bidirectional digital input module The NI 9401 is an 8-channel, 100 ns bidirectional digital input module for any NI CompactDAQ or CompactRIO chassis. You can configure the direction of the digital lines on the NI 9401 for input or output by nibble (4 bits). Thus, you can program the NI 9401 for three configurations - eight digital inputs, eight digital outputs, or four digital inputs and four digital outputs. Each channel is compatible with 5 V/TTL signals and features 1,000 Vrms transient isolation between the I/O channels and the backplane. The module includes a screw-terminal connector with strain relief as well as a D-SUB solder cup backshell for creating custom cable assemblies. Fig a) and b) show the general view of the module NI 9401 and its terminals on the connector block accordingly. 16

17 a) general view of the module NI 9401 b) terminals of NI 9401 on the connector block Fig NI 9263 analog output module The NI 9263 is a 4-channel, 100 ks/s simultaneously updating analog output module for any NI CompactDAQ or CompactRIO chassis. The NI 9263 also features ±30 V overvoltage protection, short-circuit protection, low crosstalk, fast slew rate, high relative accuracy, and NIST-traceable calibration. The NI 9263 module includes a channel-to-earth ground double isolation barrier for safety and noise immunity. Fig a) and b) show the general view of the module NI 9263 and its terminals on the connector block accordingly. а) general view of the module NI 9263 b) terminals of NI 9263 on the connector block Fig

18 1.2.9 NI 9234 dynamic signal acquisition module The NI 9234 is a four-channel C Series dynamic signal acquisition module for making highaccuracy audio frequency measurements from integrated electronic piezoelectric (IEPE) and non-iepe sensors with NI CompactDAQ or CompactRIO systems. The NI 9234 delivers 102 db of dynamic range and incorporates software-selectable AC/DC coupling and IEPE signal conditioning for accelerometers and microphones. The four input channels simultaneously digitize signals at rates up to 51.2 khz per channel with built-in antialiasing filters that automatically adjust to your sampling rate. Fig shows the general view of the module NI Fig General view of the module NI Connector block and cables Connector block (Fig. 1.1) is designed to connect the experimental modules to the modular instruments of NI cdaq-9178 system. On the left lateral side of the block are placed power supply input (which connects to an AC network (220 V) via a cable included in the laboratory stand kit) and a power switch. Inside the connector block there are 12 V and 5 V DC power supplies, the terminals of which are located on the Power supply unit part of the connector block front panel. Terminals of the following modular instruments are placed on the connector blovk front panel: NI 9474 high-speed sourcing digital output module; NI 9205 analog input module; NI channel universal C Series module; NI 9237 simultaneous bridge module; NI 9211 thermocouple input module; NI 9401 bidirectional digital input module; NI 9263 analog output module. 18

19 Connections between experimental modules and modular instruments are performed via special connector cables, included in the laboratory stand kit. Table 1.1 presents the cables list. Table 1.1 Assignment Color Length, m Q-ty 1 cable to connect BNC connectors to mini-banana connectors red/ black 0,9 1 2 cable to connect mini-banana connectors red 0,6 4 3 cable to connect mini-banana connectors black 0,6 4 4 cable to connect banana connectors red 0,6 5 5 cable to connect banana connectors red 0, cable to connect banana connectors black 0,6 2 7 cable to connect banana connectors black 0, cable to connect BNC connectors black 2 2 Fig shows the connector cables in accordance with Table , 5 6, 7 8 Fig Connector cables 19

20 2 Software description 2.1 Software activation To activate the software perform the following steps: 1. Run the software. The first time you run it, Product activation window will open (Fig ). Fig Product activation window 2. In order to receive the product activation code copy the serial number, displayed in the corresponding line, and send an request to: 3. Enter the activation code and click Apply. Note: save the activation code to use it next time you need to reactivate the software on the same computer. 2.2 Measurements Measurement sequence: 1. Run the software. Window «Measuring of physical quantities» will open (Fig ) which consists of the following sections of laboratory works: Temperature Distance Strain Pressure 20

21 Vibration Circular motion On hovering at each section, in the lower right corner of the window appears its brief description. Fig Program window «Measuring of physical quantities» 2. Select one of the sections of laboratory works. Window for selecting laboratory work of the chosen section will open. For example, the section Temperature (Fig ) consists of the following laboratory works: 1.1. Temperature measurement using thermocouples; 1.2. Temperature measurement using semiconducting thermistors; 1.3. Temperature measurement using transistor sensor. 21

22 Fig Program window «Measuring of physical quantities. Temperature» 3. Select a laboratory work from the selected section. Window for performing the chosen laboratory work will open. For example, on choosing the laboratory work 1.1 Temperature measurement using thermocouples opens the program window for performing the corresponding laboratory work (Fig ). Fig Window Temperature measurement using thermocouples 22

23 4. Windows for performing laboratory works contain the following control buttons: «Measure» runs the measurement process; «Report» generates a report of the measurement results; «New session» starts a new session; «Calculator» opens Windows standard calculator; minimizes windows; closes program windows and terminates laboratory works; applies settings. On clicking the Measure button opens the Number of measurements dialog box (Fig ). Fig Number of measurements dialog box After applying the settings, program automatically measures all given values and displays the results in the Table Measuring results in the laboratory work program window. On clicking the Report button, program automatically creates a.csv file containing a report of measuring results, which can be edited using MS Excel. On clicking the New session button, program resets current measuring results and starts a new session of measurements. On clicking the Calculator button, opens Windows standard calculator. 23

24 2.3 Working with graphs Measuring results are also visualized in a graphical form (Fig ). Fig Temperature control graph Fig shows the graph palette to move cursors, zoom or pan the display: Fig Graph palette 1. On clicking a, user may scroll the displayed graph on the graphical element. 2. On clicking b, the toolbox for zooming vertical and horizontal axes will open (Fig ). The tools in the toolbox are designed to: Fig Graphical display zoom toolbox Zoom in an area of the graph; Zoom in an area of the graph on the x-axis; Zoom in an area of the graph on the y-axis; Zoom in or out to autoscale the graph; Zoom in proportionally; Zoom out proportionally. 24

25 3. On clicking c, user may move the cursor to any point of the graph, after which in the indication elements Power and Frequency (located next to the zoom toolbox) power and frequency values will appear accordingly. 4. On clicking Auto scale, user may automatically determine and set scale ranges of a graph. 25

26 3 Ultrasound and its implementation Aim: to measure the speed of ultrasonic wave propagation under laboratory conditions; distance measurement using ultrasound. 3.1 Theory The range of mechanical vibrations which can be heard by the human ear lies between frequencies of 16 Hz and 16,000 Hz. The non-audible frequencies below 16 Hz are known as infrasound and those above 16,000 Hz as ultrasound (US). The frequency is the number of vibrations per second. Ultrasonic vibrations are used in a wide range of techniques such as purifying, metal welding, machining, metal forming, soldering, materials testing, locating, diagnosis, therapy, signal transmission, etc. Fig Ultrasonic sensor Ultrasonic sensors are based on the measurement of the properties of acoustic waves with frequencies above the human audible range, often at roughly 40 khz 1). They typically operate by generating a high-frequency pulse of sound, and then receiving and evaluating the properties of the echo pulse. Three different properties of the received echo pulse may be evaluated, for different sensing purposes. They are: Time of flight (for sensing distance) Doppler shift (for sensing velocity) Amplitude attenuation (for sensing distance, directionality, or attenuation coefficient) Time of flight. Reflection mode In reflection mode (also known as echo ranging ), an ultrasonic transmitter emits a short burst of sound in a particular direction. The pulse bounces off a target and returns to the receiver after a time interval t. The receiver records the length of this time interval, and calculates the distance travelled r based on the speed of sound c: (3.1.1) 26

27 Fig Ultrasonic reflection mode for sensing distance Very often, separate transmitting and receiving transducers are placed immediately next to each other, housed as a single unit. In these cases, the distance calculated will be twice the distance from the sensor to the target. Doppler shift When a wave reflects off of a moving object, its frequency is shifted by an amount proportional to the velocity of the object. This fact can be exploited in ultrasonic sensing by having the receiver measure not the time of flight but the frequency of the returning echo pulse. Knowing f e and f r, the frequency of the emitted and received pulse, respectively, the velocity v of the target may be calculated: ( ) ( ) (3.1.2) where A is the angle between the target's and the pulse's lines of motion. 3.2 Equipment description The following devices are used during the laboratory work: 5 V power supply; NI 9474 high-speed sourcing digital output module; NI 9401 bidirectional digital input module; NI 9205 analog input module; Distance and displacement measurement module. Hardware functional characteristics: 12 V and 5 V power supplies are used for providing power; 27

28 NI 9474 is used for controlling the stepper motor and for providing power of ultrasonic sensor and linear encoder; NI 9401 module is used for feeding a start impulse of the ultrasonic sensor and for measuring the length of echo-pulses from the ultrasonic sensor; NI 9205 is used for measuring A and B signals from the linear encoder; Distance and displacement measurement module is used for creating required physical conditions to perform laboratory works. 3.3 Order of performance of the laboratory work «Ultrasound velocity measurement» To perform the laboratory work, follow these steps: 1. Read carefully the laboratory bench description and safety precautions (ch. 1.1, 1.2). 2. Get acquainted with the laboratory work aim and the theory of temperature measurement using transistor temperature sensor. 3. Switch on the power supply of NI cdaq-9178 data acquisition system, connect the system to a computer via special USB cable, switch on the computer and the bench power supply. 4. Perform the connections presented in the Table Modules' terminals, used during the laboratory work, are presented on the Fig Fig Terminals of modular instruments 28

29 Table Contact 1 Contact V + Connector block Power supply unit V sup Connector block NI V - Connector block Power supply unit COM Connector block NI DO4 Connector block NI V Dist. and displ. mod. Sound and vibr. mod. 4 COM Connector block NI 9474 Dist. and displ. mod. Sound and vibr. mod. 5 DIO0 Connector block NI 9401 Start Dist. and displ. mod. Sound and vibr. mod. 6 DIO4 Connector block NI 9401 Echo Dist. and displ. mod. Sound and vibr. mod. 7 COM Connector block NI 9401 Dist. and displ. mod. Sound and vibr. mod. 8 DO0 Connector block NI 9474 F1 Dist. and displ. mod. Stepper motor 9 DO1 Connector block NI 9474 F2 Dist. and displ. mod. Stepper motor 10 DO2 Connector block NI 9474 F3 Dist. and displ. mod. Stepper motor 11 DO3 Connector block NI 9474 F4 Dist. and displ. mod. Stepper motor 12 COM Connector block NI 9474 Dist. and displ. mod. Stepper motor V Мод. изм. пер. и рас. Ультр. дат. рас. +12 V Dist. and displ. mod. Linear encoder 14 Мод. изм. пер. и рас. Ультр. дат. рас. Dist. and displ. mod. Linear encoder 15 Ch0 + Connector block NI 9205 A Dist. and displ. mod. Linear encoder 16 Ch1 + Connector block NI 9205 V Dist. and displ. mod. Linear encoder 17 COM Connector block NI 9205 Dist. and displ. mod. Linear encoder 5. Run the program Measurement of physical quantities. Select the section Distance, then laboratory work Ultrasound velocity measurement (Fig ). Fig Window Ultrasound velocity measurement 29

30 6. Perform the following steps in the program window Ultrasound velocity measurement : Move the reflector at a distance L 75 mm from the ultrasonic radiator (performing corresponding actions in the section Stepper motor control ); Click Measure after setting the distance L and enter 10 in the field Number of measurements of the dialog window that opens and click the Accept button. 1 2 Fig Setting the number of measurements 7. After the user applies measurement settings, the program automatically starts to measure the ultrasonic transmission total time (τ) 10 times by writing the result in the Table Measuring results of the program window. Copy the data from the Table Measurement mean values in the Table Calculate the ultrasonic velocity V i using formula an write down in the Table V i = 2L/ i (3.3.1) 9. Calculate the velocity mean value (V mean ) and the mean square value (σ) using the following formulas: (3.3.2) ( ) (3.3.3) Write down the results in the Table Calculate the systematic error component using formula and write down the obtained results in the Table

31 V = V mean V 0 (3.3.4) where V 0 is the ultrasonic velocity real value in the given conditions (take V 0 = 344 m/s at t = 20 C and V 0 = 350 m/s at t = 30 C). Table 3.3.2, [μs] V i, [m/s] V mean, [m/s] σ, [m/s] V, [m/s] 11. After you have finished the laboratory work: close the program window Ultrasound velocity measurement ; close the program window Measuring of physical quantities ; switch off the computer and the bench power supply; switch off the power supply of NI cdaq-9178 data acquisition system. 3.4 Checking questions 1. What waves are called ultrasound vibrations? 2. How is ultrasound velocity measured? 31