Question

RLC Circuit/critical damping.

Methodology for critical resistance measurements. What is the random error
associated with the uncertainty of this measurement? How can it be accounted
for ?

What you havehere is a deacde box that varies the ressitance in a circuit.

Answer 1

Uncertainty of Measurement

1.Introduction

2.Essentials of measurement uncertainties

3.Scope

4.Definition

5.ISO GUM Principles I

6.Measurement Uncertainty Estimation Protocol

7.Mathematics involved in estimating standard uncertainties

8.Expression of measurement uncertainty (for results from chemical laboratory)

9.Probability distribution

10.Case study -2

11.Pooling of Standard deviations

12.Converting information into a standard uncertainty (type B evaluations

13.Possible sources of Uncertainty in a chemical lab

14.Cause and effect analysis ( also called fish diagram)

15.References

1.Introduction

Measurement is a process, in which a set of operations are performed to determine the value of quantity. A process is an integral set of activities that uses resources to transform inputs to outputs. In a measurement process even when all the measurement factors which can be controlled are controlled, repeated observation made during under the same condition, are rarely found identical. This is due to the variables - operator, reference standards / materials / Instrument / environment, calibration, test methods and therefore measurement results are never true value and in fact accompanied with uncertainty. Therefore the "measurement uncertainty" is a property of a measurement.

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2.Essentials of measurement uncertainties

The customer needs to get an idea of the applicability of the result. Measurement uncertainty has to be taken into account particularly when regarding specification limits. Testing laboratories need uncertainties with their calibration certificates, so that they can establish the uncertainty of their own measurements. An estimation of a measurement's uncertainty is required for testing and calibration laboratories complying with ISO/IEC 17025. A calibration laboratory ... shall have and shall apply a procedure to estimate the uncertainty of measurement for all calibrations ...", Testing laboratories shall have and shall apply procedures for estimating uncertainty of measurement" The uncertainties values have to be stated in the test report depends on requirements by the test method, requirements by the customer, or whether conformance to specification has to be assessed (ISO/IEC 17025, 5.10.3). In calibration, uncertainties have to be stated in the certificate (as they are required by the user of the calibrated equipment).

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3. Scope

The purpose of this write-up is to familiarize the reader with subject of measurement uncertainty to that extent that he would be able estimate uncertainty in measurement in his laboratory.

Instead of going into theoretical aspect and in great detail this document has taken the help simple and solved examples to familiarize and develop the skill of calculating uncertainty in measurements.

The examples given cover most of the situations but the focus is on chemical testing laboratory.

Hope, those who have very little or no exposure to the estimation of uncertainty will be able to start estimating uncertainty in measurement for their kind of lab.

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4.Definition

Uncertainty is the parameter associated with the result of a measurement that characterizes the dispersion of the values that could be attributed to the measurand.

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