3) Random Errors

Apart from the assembly and environmental errors there can be many other errors which may be very difficult to trace and predict, these are called as random errors. It is even not possible to list all these random errors, but some of the prominent ones have been described below:

a) Frictional errors: There are number of moving mechanical parts in the analogue measuring instruments. The friction between these components leads to errors. Due to friction some of the parts wear and tear, which further adds to the error of the instrument. Hence, one should not use the analogue measuring instruments for long periods of time and replace with the good quality ones from time-to-time.

b) Mechanical vibrations: When the instrument is used in vibrating place the parts of the instrument start vibrating giving faulty readings.

Exercise 3. Find if the following statements are true or false. Correct them if they are false.

1. Hybrid instruments use the mechanical appliances to produce energy necessary to operate a digital readout.

2. There are two types of errors in measurements: systematic and random.

3. User should not calibrate the instrument during the term of warranty.

4. Vibrating does not influence noticeably on instrument readout.

5. Every error we can’t predict belongs to random error.

Lesson 7

ВИВЧЕННЯ ТЕРМІНОЛОГІЇ ЗА ТЕМОЮ МОДУЛЯ

Exercise 1. Learn the text and then answer the questions.

Combination instruments

For some types of work, combination instruments have been developed which, typically, have two indicating instruments with interconnecting circuitry and selector switches. These are so arranged that various testing requirements may be set up by proper switch settings. This reduces the wiring as compared to that needed for separate instruments. Time needed to set up for a particular test is reduced and possibilities of wiring errors are reduced.

Additionally, single-instrument multi-testers are available (both analog and digital) which measure both DC voltage and current as has been discussed, but in addition can measure AC voltage and (in some instances) AC current and can measure resistance. Such instruments are a great convenience to electricians.

Clamp-on instruments

A specialized type of instrument is available which is useful for measuring currents in conductors where it is desired to do so without interrupting the circuit. These are called clamp-on instruments. These typically incorporate a split or hinged ring of magnetic core material which is clamped around the conductor in which current is to be measured. Clamp-on instruments are available to measure both AC current and DC current. The sensing device may differ between the two types. Instruments designed for AC current measurement can measure an induced voltage in a coil surrounding the ring at one point with the induced voltage being proportional to the amount of current flow through the conductor. The instrument designed for DC current measurement electronically senses the distortion in the magnetic field in the clamp-on ring caused by the continuous mono-directional current flow.

Both types of instruments are available to cover a wide range of full scale current.

At least one maker of DC clamp-on instruments can supply clamp-on rings in various diameters from smaller sizes for wires or cables to large rings that can surround pipes.

Computer-compatible instruments

With the continuing development of computer usage, the appearance of computer-compatible field-testing instruments was inevitable. Typically, this is an adjunct to electronic testing instruments that permits the worker to store recorded data on command in some form of internal storage device (RAM, ROM, tape, disc, etc.) incorporated in the instrument. Numerical measurements can be supplemented with coded information as to location and type of test plus supplementary information appropriate to the test being made. This data can also normally be recorded and then downloaded into a PC computer for more detailed analysis while in the field.

Storing information in the above fashion reduces field time in data taking. The stored information can also be later transferred to a desktop computer that can be used to record, analyze and process the data in accord with record keeping programs that have been developed for the operating company's purpose.

1. Give examples of combination electric instruments. What are its areas of application? What are advantages and disadvantages of such kind of meters?

2. What are special advantages of so-called clump-on instruments?

3. Why do you think is very convenient to store instrument readouts in electronic form?

4. What additional conveniences could be given to computer-compatible instruments owing to wireless technologies?

ГРАМАТИЧНІ ВПРАВИ

Reviewing adverb clauses of time (Module 4, Lesson 2)

Exercise 1. Complete the sentences using appropriate verb tenses.

1. Bye-bye. I (phone) _______ you again when I (get) ______ home.

2. I’m sure it will stop raining soon. As soon as it (stop) ________, I (leave) __________ home.

3. I (listen) ______________ to English records while I (sleep) _________. Do you think it will improve my English learning?

4. He’s going to leave tomorrow. However he promises to give us detailed instructions before he (leave) ___________.

5. I’ll get there around six. I (wait) ______________ for Tom until he (come) ___________.

Exercise 2. Translate the following sentences into English.

1. Я зроблю це, коли повернусь.

2. Я вже закінчу листа до того часу, коли ви повернетесь.

3. Коли я йшов сюди, я зустрів вашого брата.

4. Поки ви будете обідати, я почитаю газету.

5. Ми відправимось, як тільки отримаємо телеграму.

6. Джон вам зателефонує як тільки він повернеться.

Комунікативна практика

Solving problems while phoning

Exercise 1. What would you say under the following circum­stances.

1. You have dialed the wrong number.

2. Someone else has dialed the wrong number.

3. There is an interference on the line.

4. Your English is not very good.

5. You were suddenly disconnected.

6. You didn't comprehend what someone said.

7. You want the person to stop speaking so fast.

8. You want the person to speak louder.

Help for you: possible phrases in an arbitrary order.

1. I'm sorry to have bothered you.

2. Could you speak up, please?

3. I'm afraid we were cut off.

4. This is a bad line, I can't hear you.

5. Could you speak slowly, please?

6. I'm sorry, I think you have the wrong number.

7. I'm sorry, I don't speak English very well,

8. I'm sorry, I didn't understand/catch that.

Exercise 2. Find some question corresponding to the following answers.

1. I’d like to speak to someone about a bill.

2. I’ll hold on.

3. This is Vasily Kuznetsov from National Aviation University.

4. Yes of course. I’ll put you through to the laboratory.

5. Never mind.

6. Yes, I’ll call back then.

7. None at all, good bye.

8. I’ll take sure she gets the message.

9. K-U-Z-N-E-T-S-O-V.

10. +38 050 2322322

Вправи для самостійної роботи

Exercise 1. Read an advertising material for clamp-on heat meter an then prepare short description of main principles of action and characteristics of offered instruments.

Fixed installed and portable clamp-on heat meters

• External temperature and heat quantity measurements

• Clamp-on flow and PP100 temperature sensors

• Portable and fixed installation instruments

• For all commonly used pipe materials

• Pipe diameters from 10 mm to over 3,000 mm

• For process temperatures from -30 °C to +200 °C

• Bi-directional flow measurement

• Intuitive instrument menu

• Setup Wizard for easy and quick meter programming

• Unique Audible Sensor Positioning Assistant

CATronic clamp-on ultrasonic flow meters equipped with the optional heat quantity measurement function have been used for many years as portable and permanently installed heat meters by businesses of various industries and municipal organizations all over the world.

Due to their capability of determining energy transmission, they are particularly useful for the building services activities and are also frequently used within the food and drink industry where heating and chilling applications are essential parts of the production process.

The clamp-on mounting technique of the flow and temperature sensors enables the flow meters to measure the heat quantity non-invasively and non-intrusively from outside the pipe. For this reason there is no need to cut into the pipe and therefore no interruption of flow, no pressure drop, and no risk of leakage.

The portable CATflow 230 can be used for spot measurements as part of energy consumption surveys on heat exchangers, heating and chilling lines, HVAC systems (Heating, Ventilating, and Air Conditioning), and boilers. In the case of retrofit situations, the CATflow 150 flow meter is the ideal solution for permanent installation. With various process inputs, outputs and serial interfaces, the CATflow 150 can easily be embedded into automated control systems, and can act as an additional control unit for heating and cooling systems.

How it works

A set of ultrasonic flow sensors is installed on a suitable pipe section along with two PP100 temperature sensors which are mounted to the pipe at the inlet and outlet of the chosen location. From the specific heat capacity of the flowing medium, the energy transmission can be determined using the calculated mass flow rate and temperature difference between the inlet and outlet.

General information

The ultrasonic flow sensors cover a pipe diameter range from 10 mm to over 3,000 mm (0.4 to 118 inch) and work on any common pipe material and temperatures from -30 °C to +200 °C. The PP100 clamp-on temperature sensors supplied with the flow meter match this temperature range and can be easily connected to the flow meter.

Parameters of the measurable liquids are stored on the transmitter and can be chosen from a menu. This includes commonly used heating media such as hot water and oil, as well as refrigerants such as chilled water, water/glycol mixes and R-coded chemical refrigerants.

The CATflow 230 and CATflow 150 feature an internal data logger with a capacity of up to 100,000 samples, which stores all measured and totalized values and parameter sets. When equipped with a data logger, the flow meters are supplied with the CATdata+ software which enables the user to download and view the flow data on a computer. The data can be transferred via the instrument’s RS 232 interface for which an RS 232 to USB converter cable can be supplied.

Both the CATflow 230 and CATflow 150 offer process outputs including 0/4…20 mA current outputs, open-collector outputs with totalizer pulse, and digital relay outputs. Additionally, the CATflow 150 can be equipped with an RS 485 interface. Apart from the units specific to the heat quantity measurement function, the CATronic flow meters display various units for the volumetric flow rate, flow velocity, mass flow rate, flow volume and mass.

Ease of use

Every instrument of the CATflow series of clamp-on ultrasonic flow meters can be set up and measurements be obtained within a matter of minutes. This is made possible by their intuitive menu structure and Setup Wizard function, which guide the user step by step through the configuration process. Additionally, the flow meters offer the unique Audible Sensor Positioning Assistant - a new intelligent sensor location function which assists the user during the sensor installation process by giving real-time graphical instructions and audible signals.

Typical applications

• Boiler and air conditioning system controlling

• Balancing of heating and cooling systems

• Inspection of air conditioning units

• Energy consumption surveys

Exercise 2. Be ready to discuss possible applications of clamp-on instruments, as well as probable methods of non-contact measurement of different physical parameters.

Lesson 8

Підготовка до модульної контрольної роботи

Revision of topics discussed in lessons 1-7. Every students of the group makes a report devoted to measuring instruments: their history, present status and prospects for the future.

Вправи для самостійної роботи

The following exercises are typical for tasks that could be offered to students during module test.

Exercise 1. Translate the text in written.

The altimeter indicates the altitude above sea level or the ground in feet. The barometric altimeter is an aneroid barometer. It measures variations in air pressure with changes in altitude. A metal diaphragm is housed in a case connected to the static tube. The diaphragm expands and contracts as air pressure in the case changes. Levers and gears connect the diaphragm to a pointer.

The altimeter reads zero at the average sea-level pressure of 29.92 inches. At different geographical locations the barometric pressure varies according to the elevation and weather conditions. The pilot en route radios for the local sea-level barometric reading and adjusts his altimeter to this setting with a knob. When landing he asks the controller for the airport barometric pressure and adjusts his altimeter to show the height above the runway.

The absolute altimeter, or terrain-clearance indicator, gives the height of the plane above the Earth. It measures the time lapse between the transmission of a radio signal to the ground and its return. The rate-of-climb, or vertical-speed, indicator shows the rate of ascent or descent in thousands of feet per minute.

Exercise 2. Fill in the blanks using the terms of module 7.

1. Other types of readout utilizes LCD (____________________) elements.

2. Such a diode is normally a neutral light color because it reflects light, but when energized by an ___________ signal, it appears as a dark bar (absorbs light) which contrasts with the light background color.

3. Of the two types, the liquefied crystal ____________ are normally used in test instruments since they take less energy from the instrument batteries and can be easily read in bright sunlight.

4. The discussion herein assumes that ___________ crystal readout displays will be used.

5. The direct current ___________, as its name implies, amplifies the input signal to a value that will actuate the readout module after adjustment using the range selector module.

Exercise 3. Explain the terms below with other words.

Readout, display, pointer, clamp-on instrument, operating coil, amplifier, output.

Exercise 4. Choose the one word or phrase that best complete the sentence.

1. Kansas _______ at the geographical center of the US.

1. it is located

2. the location is

3. its locations

4. is located

2. Since the eighteenth century, ________ the major genre of literature in most literate societies.

1. becoming the novel

2. has the novel become

3. a becoming novel

4. the novel has become

3. In concrete poetry, the primary consideration is the way that _______ in the poem.

1. words are arranged

2. the arrangement of words

3. arranging the words

4. words in an arrangement

4. The U.S. Metric Conversion Act, which President Ford ________ in 1975, outlined a policy of voluntary conversion to the metric system.

1. signed

2. signing

3. signing him

4. he signed

5. Komodo dragons, which average eight feet in length, ________ largest lizards.

1. the world’s

2. is the world’s

3. the world’s

4. are the world’s

6. Chicago is home to more than four million people ________ as many as fifty-four languages and dialects.

1. speak

2. they speak

3. spoke

4. speaking

7. About three fourth of the books published in the United States are put out by publishers _______ in New York City.

1. located

2. locates

3. they locate

4. they are located

8. Diamond is the only mineral ________ cut and polished in the same operation.

1. can be

2. it can be

3. that can be

4. what can be

Exercise 5. Identify the one underlined word or phrase that must be changed in order the sentence to be correct.

1. The apple tree appears in the mythology, traditions, historical, and archeology of the most ancient nations.

2. The first horse-drawn chariots were introduce around 2500 B.C.

3. Not only the Etruscan alphabet and the Latin alphabet are descendents of the Greek alphabet.

4. During their first attempts as a song writer, George Gershwin diligently continued to study the piano, harmony, theory, and orchestration.

5. Early television sets such as the RCA Victor model had small screens but containing a mass of additional components.

6. The cliff dueling in Messa Verde were built in the thirteenth century by native Americans which farmed the green plateau.

7. The poet Walt Whitman was an easy recognized figure with his long, white board and wide-brimmed hat.

8. Someone who personifies the “American dream” are Andrew Carnegie, who immigrated to the United States from Scotland without money and made millions in the steel industry.

Exercise 6. Complete the sentences using the verbs in brackets in appropriate form (finite or non-finite). Add auxiliary verb if necessary.

1. For full scale deflection of the meter pointer, the meter shunt (provide) __________ a path for the portion of the current in excess of that (require) __________ by the sensitivity of the meter movement.

2. Assume that the movement sensitivity of the meter in the above figure (be) ___________ one ampere.

3. With the addition of the proper shunt resistance, the ammeter circuit (allow) __________ a total of 5 amperes (pass) _________ before the pointer (indicate) _________ full-scale deflection—4 amperes through the shunt and 1 ampere through the movement.

4. Therefore, the maximum current (read) _________ ability of the ammeter (increase) ______________by the addition of the shunt resistor.

5. Temperature sensors (supply) _______________ with the flow meter match this temperature range and can easily (connect) _____________ to the flow meter.