Instrumentation Lab

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  • Topic: Multimeter, Electronic test equipment, Metrology
  • Pages : 7 (1511 words )
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  • Published : March 4, 2013
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Jordan University of Science and Technology
Faculty of Engineering
Mechanical Engineering Department

Title :Calibration of Instruments .
Course # :ME 472.
Dr : Mohammad Othman
Name : Afnan Rowhi al Bahlool .
Student number : 20080025118.

Objective :
* Get familiar with the pressure gages, such as U tube manometer , deadweight and calibrate them with pressure gage . * Get familiar with some electrical instruments , such as the DC power supply, AC power supply (function generator ), digital and analog multi-meters . * Study how to calibrate these instruments.

* study the hysteresis phenomena .

Introduction :
calibration is often regarded as including the process of adjusting the output or indication on a measurement instrument to agree with value of the applied standard, within a specified accuracy. 

Although the exact procedure may vary from product to product, the calibration process generally involves using the instrument to test samples of one or more known values called “calibrators

Calibrations are performed using only a few calibrators to establish the correlation at specific points within the instrument’s operating range.

Calibration may be called for:
* a new instrument
* after an instrument has been repaired or modified
* when a specified time period has elapsed
* when a specified usage (operating hours) has elapsed
* before and/or after a critical measurement
* after an event, for example after an instrument has had a shock, vibration, or has been exposed to an adverse condition which potentially may have put it out of calibration or damage it sudden changes in weather * whenever observations appear questionable or instrument indications do not match the output of surrogate instruments * as specified by a requirement, e.g., customer specification, instrument manufacturer recommendation.

Hysteresis :

 a delay in the response of an object to changes in the forces acting on it, especially magnetic forces  in which an induced or observed effect remains after the inducing cause is removed. In this way, two physical quantities are related in a manner that depends on whether one is increasing or decreasing with respect to the other. There are various examples, including magnetic hysteresis,electric hysteresis, and thermal hysteresis.

this phenomenon should be studied carefully, because in some applications, many explanations can be executed usin difference, such as the loss of energy in the magnetic .

Figure 1 pressure hysteresis

Equipment and instruments :

Negative pressure :
A way of expressing vacuum; a pressure less than atmospheric or the standard 760 mmHg (101,325 pascals). 
Which is used  to refer to a situation in which an enclosed area has lower pressure than the area around it. Any compromise in the divide between the area of negative pressure and the more highly pressurized area around it would cause substances to flow into the area of negative pressure.

 Negative pressure is useful for a number of applications, including the prevention of oil spills, quarantine of highly contagious patients, and in the household vacuum cleaner.
 Negative pressure can also be dangerous, as is the case when municipal waterlines lose pressure, potentially sucking contaminated groundwater up into the water supply. 

2. Dead weight tester :
* Deadweight testers are the basic primary standard for accurate measurement of pressure. Deadweight testers are used to measure the pressure exerted by gas or liquid and can also generate a test pressure for the calibration of numerous pressure instruments. 

* Known weights are placed on a rotating plate on top of a calibrated piston, connected by tubing to the pressure sensor being tested. This puts a known force (weights) on a known surface area (piston). The rotation eliminates any static friction that would affect the...
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