Sensors lab - Metrisys · NI 9401 bidirectional digital input module; NI 9263 analog output module;...

Sensors lab

User Manual

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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.

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Table of contents

Annotation ....................................................................................................................................... 2

Table of contents ............................................................................................................................. 3

Safety precautions ........................................................................................................................... 4

1 Educational laboratory test bench ........................................................................................... 5

1.1 Experimental modules ...................................................................................................... 6

1.1.1 Temperature measurement module ........................................................................... 6

1.1.2 Strain-gage measurement module ............................................................................. 7

1.1.3 Pressure measurement module .................................................................................. 8

1.1.4 Distance and displacement measurement module ..................................................... 9

1.1.5 Vibration measurement module ................................................................................ 9

1.1.6 Sound and vibration measurement module ............................................................. 10

1.2 NI cDAQ measurement system ...................................................................................... 11

1.2.1 NI cDAQ 9178 data acquisition system .................................................................. 12

1.2.2 NI 9474 high-speed sourcing digital output module ............................................... 12

1.2.3 NI 9205 analog input module .................................................................................. 13

1.2.4 NI 9219 4-channel universal C Series module ........................................................ 14

1.2.5 NI 9237 simultaneous bridge module ..................................................................... 15

1.2.6 NI 9211 thermocouple input module ...................................................................... 16

1.2.7 NI 9401 bidirectional digital input module ............................................................. 16

1.2.8 NI 9263 analog output module ................................................................................ 17

1.2.9 NI 9234 dynamic signal acquisition module ........................................................... 18

1.3 Connector block and cables ............................................................................................ 18

2 Software description .............................................................................................................. 20

2.1 Software activation ......................................................................................................... 20

2.2 Measurements ................................................................................................................. 20

2.3 Working with graphs ...................................................................................................... 24

3 Ultrasound and its implementation ....................................................................................... 26

3.1 Theory ............................................................................................................................. 26

3.2 Equipment description .................................................................................................... 27

3.3 Order of performance of the laboratory work «Ultrasound velocity measurement» ..... 28

3.4 Checking questions ......................................................................................................... 31

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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.

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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».

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.

Pressure measurement

module

Sound and vibration measurement

module

Strain-gage measurement

module

Temperature measurement module

Vibration measurement

module

Connector block

Distance and displacement

measurement module

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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.

1.1.1 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. 1.1.1).

Fig. 1.1.1 - 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. 1.1.2 shows the internal structure of the module.

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Fig. 1.1.2 – Module’s schematic structure

1.1.2 Strain-gage measurement module

The strain-gage measurement module (Fig. 1.1.3) 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. 1.1.3 – 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.

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1.1.3 Pressure measurement module

Pressure measurement module (Fig. 1.1.4) 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. 1.1.4 – 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.

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1.1.4 Distance and displacement measurement module

Distance and displacement measurement module (Fig. 1.1.5) 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. 1.1.5 – 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.

1.1.5 Vibration measurement module

Vibration measurement module (Fig. 1.1.7) consists of:

vibration source;

vibration sensor (acceleration).

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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. 1.1.6.

Fig. 1.1.6 – 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. 1.1.7 – General view of the vibration measurement module

1.1.6 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. 1.1.8) 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);

Y

X

1

2

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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).

Fig. 1.1.8 – 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 9219 4-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. 1.2.1 shows the general view of the measurement system.

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2

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Fig. 1.2.1 – General view of NI cDAQ measurement system

1.2.1 NI cDAQ 9178 data acquisition system

The NI cDAQ-9178 (Fig. 1.2.2) 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. 1.2.2 – General view of NI cDAQ 9178 chassis

1.2.2 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.

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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. 1.2.3 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. 1.2.3

1.2.3 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. 1.2.4 shows the NI 9205 terminals assignment.

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Fig. 1.2.4 – NI 9205 terminals assignment




Fig. 1.2.5

1.2.4 NI 9219 4-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.



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Fig. 1.2.6

1.2.5 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. 1.2.7

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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. 1.2.8

1.2.7 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.



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a) general view of the module NI 9401 b) terminals of NI 9401 on the connector block

Fig. 1.2.9

1.2.8 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. 1.2.10

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1.2.9 NI 9234 dynamic signal acquisition module

The NI 9234 is a four-channel C Series dynamic signal acquisition module for making high-

accuracy 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. 1.2.11 shows the general view of the module NI 9234.

Fig. 1.2.11 – General view of the module NI 9234

1.3 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 9219 4-channel universal C Series module;

NI 9237 simultaneous bridge module;

NI 9211 thermocouple input module;


NI 9263 analog output module.

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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 0,17 2

6 cable to connect banana connectors black 0,6 2

7 cable to connect banana connectors black 0,17 2

8 cable to connect BNC connectors black 2 2

Fig. 1.3.1 shows the connector cables in accordance with Table 1.1.

Fig. 1.3.1 – Connector cables

1 2 3

4, 5 6, 7 8

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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.

2.1.1).

Fig. 2.1.1 – “Product activation” window

2. In order to receive the product activation code copy the serial number, displayed in the

corresponding line, and send an e-mail request to: [email protected].

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. 2.2.1)

which consists of the following sections of laboratory works:

Temperature

Distance

Strain

Pressure

[email protected]

mailto:[email protected]:[email protected]

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Vibration

Circular motion

On hovering at each section, in the lower right corner of the window appears its brief

description.

Fig. 2.2.1 – 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. 2.2.2) 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.

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Fig. 2.2.2 – 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. 2.2.3).

Fig. 2.2.3 – Window “Temperature measurement using thermocouples”

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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. 2.2.4).

Fig. 2.2.4 – “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.

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2.3 Working with graphs

Measuring results are also visualized in a graphical form (Fig. 2.3.1).

Fig. 2.3.1 – Temperature control graph

Fig. 2.3.2 shows the graph palette to move cursors, zoom or pan the display:

Fig. 2.3.2 – 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.

2.3.3).

Fig. 2.3.3 – Graphical display zoom toolbox

The tools in the toolbox are designed to:

‒ 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.

http://zone.ni.com/reference/en-XX/help/371361K-01/lvconcepts/customizing_graphs_and_charts/#Autoscaling

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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.

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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. 3.1.1 – 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)

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Fig. 3.1.2 – 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 fe

and fr, 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;




Distance and displacement measurement module.

Hardware functional characteristics:

12 V and 5 V power supplies are used for providing power;

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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 3.3.1. Modules' terminals, used during

the laboratory work, are presented on the Fig. 3.3.1.

Fig. 3.3.1 – Terminals of modular instruments

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Table 3.3.1

Contact 1 Contact 2

1 12 V + Connector block – Power supply unit Vsup Connector block – NI 9474

2 12 V - Connector block – Power supply unit COM Connector block – NI 9474

3 DO4 Connector block – NI 9474 +12V 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




12 COM Connector block – NI 9474 Dist. and displ. mod. – Stepper motor

13 +12 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. 3.3.2).

Fig. 3.3.2 – Window “Ultrasound velocity measurement”

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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.

Fig. 3.3.3 – 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 3.3.2.

8. Calculate the ultrasonic velocity Vi using formula 3.3.1 an write down in the Table

3.3.2.

Vi = 2L/i (3.3.1)

9. Calculate the velocity mean value (Vmean) and the mean square value (σ) using the

following formulas:

∑

(3.3.2)

√

∑( )

(3.3.3)

Write down the results in the Table 3.3.2.

10. Calculate the systematic error component using formula 3.3.4 and write down the

obtained results in the Table 3.3.2.

1

2

31

V = Vmean – V0 (3.3.4)

where V0 is the ultrasonic velocity real value in the given conditions (take V0 = 344 m/s

at t = 20 C and V0 = 350 m/s at t = 30 C).

Table 3.3.2

№ , [μs] Vi , [m/s]

1

2

3

4

5

6

7

8

9

10

Vmean, [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?

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