Anglicky v odborných předmětech "Support of teaching technical subjects in English “

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Anglicky v odborných předmětech "Support of teaching technical subjects in English “. Tutorial : Mechanic - electrician Topic : Electric measurement the 2nd. y ear Measuring devices 3 Prepared by: Ing. Jiří Smílek.

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## Anglicky v odborných předmětech "Support of teaching technical subjects in English “

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### Anglicky v odborných předmětech"Support ofteachingtechnicalsubjects in English“

Tutorial: Mechanic - electrician

Topic: Electric measurement

the 2nd. year

Measuringdevices 3

Prepared by: Ing. Jiří Smílek

Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002

je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

• Measuring range:
• Measuring range ​​reflects the range of values ​​within which the instrument measures with the required accuracy
• Usually the measuring range coincides with a full scale,
• Instrument sensitivity :
• The sensitivity of the device indicates how the deflection of the hands responds to the unit of the measured values.
• Constant device for
• is the reciprocal of sensitivity;
• expresses the size of the measured variables at one scale interval.
• formula
• unit V/div, A/div, V . A/div
• Changing the measuring range:
• DC
• Ampere meter– shaft
• Voltmetr– ballast
• AC - also
• Ampere meter– measuring transformer current - MTP
• Voltmeter-measuring transformer voltage-MTN
• Calculation of constants:
• Shunt, ballast - n times increases the range
• kP = n k
• MTP - transfer of the transformer p= I/5A
• Conversion constant transformer
• KT =p kA
• MTN - transfer of the transformer p= U/100V
• Conversion constant transformer
• KT =p kV
• W – meter
• k= range U x range I / number of scale intervals
• Accuracy of measuring instruments:
• expresses the class of accuracy.
• according to standard: 0,05, 0,1, 0,2, 0,5, 1, 1,5, 2,5 a 5.
• These numbers indicate the measured values ​​of variables leaving the maximum deviation from the actual size, in% of measuring range
• To measure accurately, the deflection of the hands must be measured in the last third of the scale.
• formula
• Overload means the multiples of the rated current or voltage, that the measuring instrument will last for a period of time without damage
• voltmeters doubled,
• ammeters tenfold,
• Power consumption devices:
• Power necessary to achieve full deflection of the hands
• Overload means the multiples of the rated current or voltage, that the measuring instrument will last for a period of time without damage
• voltmeters doubled,
• ammeters tenfold,
• Rapid stabilization of displacement of the hands:
• Reading measurement values ​​- after stabilization of the position of the hands -> longer measurement time.
• Prevention - damping oscillation rotation of the system.
• Errors of measuring instruments:
• influencing variables, which can alter the measurement data. They are for example:
• ambient temperature,
• strange magnetic fields,
• position of the device,
• frequency,
• wave alternating current,
• influence of ferromagnetic bar
• Reference conditions
• are the sum of the reference values ​​given by the instrument manufacturer for each influence quantity,
• The reproducibility of measurements
• Each correct measurement must be reproducible.
• This means that repetition with a certain measurement by the same device under the same conditions we get the same results.
Activities for students–questions
• Describe what is a measuring range
• Write how the measuring range is related to the scale
• Describe what is the instrument sensitivity
• Write a formula
• Describe what is a constant unit
• Write a formula
Activities for students–questions
• Write how to express accuracy of the meter
• Name the class of accuracy according to the standard
• Describe what we have to watch to gauge accuracy (as far as possible)
Activities for students–questions
• Write what is meant by overload (thus how we state it)
• Name some variables affecting the measurement accuracy
• Describe what we must do, in order for us to repeat measurements to achieve the same conditions
Bibliography
• Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7.
• Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.