Basics of Control and Test Methods
Classification of control methods. Existing methods of control differ in the multiplicity and variety of the physicochemical principles used in them . They are classified according to various criteria:
• stages in the production process (input, current, acceptance);
• the product is ready for operation after the control (destructive, non-destructive);
• the degree of human participation in the implementation of control ("manual", semi-automatic, automatic);
• the degree of coverage of products control (solid, selective);
• the kind of load acting on the product (mechanical, climatic, electrical and radiation).
For quality control in the standards and technical specifications (TU), selective or continuous monitoring is established on the products .
Custom Control is shown in the following cases:
• The amount of the batch presented allows the use of statistical control methods (in this case, the batch quantity must be at least twice the sample size);
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• Destructive testing methods are applied;
• there is a significant expenditure of resources during testing;
• The tests are of high cost and complexity.
When sampling, plan one or
two-stage control, determining the volume of samples, whose products are directly subjected to testing, and acceptance numbers.
With one-step control, tests are performed on a single sample. With two-step control, in addition to the primary control, there is also a re-sample that is tested when a fault is received in the primary sample. For example, tests in groups P-2, P-3, P-6 presuppose a two-stage control, P-4, P-5 - single-stage control.
Correct determination of the sample size of products is one of the key issues of acceptance control, ensuring the reliability of the results obtained. Too much sample size can lead to unacceptable losses of time and money. However, if the sample and test time are too small, there can be justified doubts about the reliability of the results obtained. Optimal are such a sample and such a test time that it is possible to achieve reliable results with a minimum cost of testing and maximum efficiency of obtaining the results.
The alternative to selective control is Solid Control , which is used in all other cases.
Methods for measuring electrical parameters
Quality control of products usually involves checking the elements and components that make up its components - resistors, capacitors, diodes, transistors, integrated circuits (ICs), etc.
Tests (measurements) of products (including integrated circuits, etc.) are subdivided into functional and parametric ones.
Functional control is reduced to verifying the correct execution of the products laid down by the developers of the functions. The control is performed by matching the output signals of a given sequence of input testing actions.Parametric control consists of measuring static and dynamic characteristics and comparing the data obtained with the parameters and characteristics contained in the product specification.
During the measurement of dynamic characteristics (varying in time), the time parameters and the amplitude of the measuring pulse are monitored.
The measurement of static characteristics (ie, constants in time) is performed at constant voltages at all electrodes of the device.
Automated measuring systems are used to measure parameters and product characteristics (for example, microchips). All of them are built on the basis of separate, carefully selected measuring devices, the switching and synchronization of which are carried out according to a specified program, and the recording of measured values of parameters and characteristics is carried out automatically.
Special executive mechanisms implement a sorting based on a number of characteristics that determine the criterion "pass-not-fit" or by the tolerance groups of parameters, i.e. Parties with different tolerances of instrument quality levels.
Product testing is a group of operations that simulate real or extreme operating conditions in order to identify potentially unreliable products.
Test conditions and a list of controlled parameters are specified in private and general technical conditions (OTU), which are, as a rule, industry standards that contain norms and specific requirements relating to specific types of products.
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Depending on the goals, the tests can be divided into two groups: 1) research - to study certain properties of products; 2) control - to assess the quality of products.The research trials are divided into boundary - to determine the dependencies between the maximum allowable values of product parameters and operational and comparative - for comparison of quality characteristics (conducted for several types of products).
The larger group is control tests , which include:
• Acceptance - are carried out at the acceptance inspection of the quality of each batch of products submitted for delivery;
• periodic - are carried out for the purpose of periodically monitoring the quality of products, confirming the stability of the technological process of their production and the probability of failure-free
work on a special program and methods of processing test results;
• Qualification - are performed in order to check the workflow of the technological process, evaluate the readiness of production for serial production of products and verify compliance with the requirements of standards and specifications;
• typical - are carried out after making changes in the design and technology of manufacturing products to assess the effectiveness and appropriateness of these changes;
• preservation tests - are conducted to confirm the minimum retention period established in the standards and specifications for the product;
• durability tests - are implemented to confirm the values of the minimum operating time established in the standards and specifications for the product;
• test - are performed to check the customer's research organization of serial production products to meet the full scope of the requirements of standards and specifications for the product, as well as to develop recommendations for improving the quality, improving the control system and setting additional requirements , entered in the technical documentation (if necessary).
The composition of the tests included in each category can be divided into groups. Each group can include one or more kinds of tests.
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