Static & dynamic characteristics of instruments

All the types of characteristics regarding static and dynamic has been discussed with images

1. STATIC & DYNAMIC CHARACTERISTICS Submitted by Kaavya B Holy Cross College, Trichy

2. PERFORMANCE CHARACTERISTIC STATIC DYNAMIC

3. STATIC CHARACTERISTICS ? Static characteristics refer to the characteristics of the system when the input is either hold constant or varying very slowly with time.

4. STATIC CHARACTERISTICS Accuracy & Precision Repeatability & Reproducibility Resolution Threshold Range or Span Linearity Sensitivity Drift Static error Dead zone Stability Bais Tolerance Hysteresis k

5. DYNAMIC CHARACTERISTICS ? Dynamic characteristics refer to the performance of the instrument when the input variable is changing rapidly with time. The dynamic performance of human eye cannot be said to be very satisfactory.

6. DYNAMIC CHARACTERISTICS Speed of response Fidelity Dynamic error Lag Overshoot Step response Ramp response

7. STATIC

8. ACCURACY & PRECISION Accuracy indicates the closeness of the measured value with the actual or true value, and is expressed in the form of the max error as a percentage of full scale reading. Precision is a measure of the reproducibility of the measurements. (group of measurements) k

9. TYPES OF ACCURACY & PRECISION Types of Accuracy: Point accuracy Accuracy as percentage of scale span Accuracy as percentage of true value Types of Precision : Conformity Significant figures

10. ACCURACY TYPES POINT ACCURACY (particular point) ACCURACY AS % OF SCALE SPAN (uniform scale –thermometer) ACCURACY AS % OF TRUE VALUE (error % of true value)

11. PRECISION TYPES CONFORMITY (resistor value ---because of limitation of scale error is created SIGNIFICANT FIGURES

12. FORMULA % of TV= (MV – TV) x 100 / TV % of full scale deflection =( MV – TV) x 100/Max scale value. PRECISION = Measured range / σ e

13. D/BW Accuracy & Precision ACCURACY PRECISION It represents the degree of correctness of the measured value w.r.t TV It represents degree of repeatability of several independent measurements of desired input at same conditions It depends on systematic errors It depends on factors that cause random or accidental errors.

14. REPEATABILITY & REPRODUCIBILITY It is defined as the ability of instrument to reproduce a group of measurements of same measured quantity by same observer using same instruments & conditions. Variation of scale reading over a given period of time.

15. RESOLUTION It is the min change or smallest increment in the measured value that can be detected by instruments. It can be L.C of instruments Resolution = Δ I / ( I max – I min ) x 100

16. THRESHOLD It is defined as the range of different input values over which there is a constant output value.

17. RANGE OR SPAN The range of an measuring device is specified by the min & max values of an instrument for which it is designed to measure.

18. LINEARITY It is the ability of an instrument to reproduce its input linearly . Linearity = Max deviation of output from idealized straight line / actual readings

19. SENSITIVITY Sensitivity = Δ output / Δ input --- at a steady state In instruments deflection factor = magnitude of measured quantity / magnitude of response k

20. DRIFT It is a departure in the output of the instrument over the period of time , where in input does not change Zero drift ( entire calibration changes with same value Span drift ( changes proportionally) Zonal drift ( particular region)

21. STATIC ERROR It is the deviation from the TV of the measured variable. Involves the comparison of an unknown with a measured standard one Static error = E s / E v x 100

22. DEAD ZONE It is an area where no action occurs the system is dead. Range of input values over which there is no change in output value. Used in voltage regulators.

23. STABILITY The ability of an instrument to retain its performance throughout its specified storage life and operating life. 5ml of fuel sample is enough OXIDATION STABILITY CHECKER

24. BAIS Constant error which exists over the full range of measurement of an instrument. Eg . Zero error

25. TOLERANCE Max allowable error that is specified in terms of certain values while measurement. It specifies the max allowable deviation of a manufactured device from a mentioned value.

26. HYSTERESIS It is a phenomenon under which measuring instrument shows different output effects during loading & unloading. It can be eliminated by taking readings in both direction & then taking mean. When input of an instrument is varied from zero to its full scale & then if the input is decreased from its full scale to zero, the output varies. The output at the particular input while increasing & decreasing varies because of internal friction.

27. DYNAMIC ( input changes with time )

28. 2 INPUTS Transient response : part of the response which goes to zero as the time becomes large. Steady state response : It has a definite periodic cycle

29. SPEED OF RESPONSE Rapidity with which a measurement system responds to changes in measured quantity. It shows how active and the fast the system is

30. FIDELITY It is the ability of the system to reproduce the output the same as the input without dynamic error. If output varies linearly with input then the system is 100% fidelity It does not depend on time and phase of input

31. DYNAMIC ERROR The difference between the TV quatity changing with respect to time and the measured quantity with respect to time k

32. LAG Every system requires its own time to respond to changes in input. This time is called as lag. RETARDATION LAG: As soon as there is a change in the measured quantity, the system begins to respond faster. TIME DELAY: The change occurs after some time , begins after a dead time , after the application of the input.

33. OVERSHOOT

34. STEP & RAMP RESPONSE The measuring instrument measuring the one steady step value to another steady step value, the in B/W these 2 values is called step response. (ice to hot) The value of response time in B/W 2 response changes very slowly with time. (Only ice ) k

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