Key questions

3.1 Why EFCs are related to high accuracy and universal measuring tool?

3.2 What is the main point of measuring method of EFC?

3.3 Explain the principle of EFC work by modes:

- frequency;

- time interval;

- frequency ratio.

3.4 List the errors that occur in EFC in different modes of work.

3.5 Find out methods of decreasing of measurement errors.

3.6 Explain how the total error determines in different work mods.

3.7 Explain how to determine the position of decimal point in different work mods.

 

Home task

4.1 Research the structural scheme of given EFC and the principle of work in different modes. To draw the structural scheme of EFC.

4.2 Using the technical characteristics of EFC choose time counting that provides the minimal error in frequency measuring mode. The result show in table 4.1. The variants of the tasks given in table 1 (appendix A); here .

 

Table 4.1 – Basic characteristics evaluation in “FREQUENCY MEASURMENT” mode.

ƒs, kHz	Тcount, ms	Expected result, kHz	∆ N, Hz	N	δ N

 

4.3 Using the technical specifications of EFC choose the parameters of period measurement mode that provide minimal measurement error of interval. The result is show in table 4.2. It is recommended to provide calculations on same frequencies as in table 1 (appendix A).

 

Table 4.2 – Basic characteristics evaluation in “PERIOD MEASURMENT” mode.

ƒs, kHz	n	Т м	Expected result (ms, µs)	∆ N	N	δ N	Тcount, ms

 

4.4 Using technical specifications of EFC choose parameters of the frequency ratio mode that will provide minimal measurement error. The results show in table 4.3 (the frequencies are given in appendix A).

 

Table 4.3 – Basic characteristics evaluation in “FREQUENCIES RATIO” mode.

ƒ1/ƒ2	n	Expected result	∆ N	N	δ N	Тcount, ms

 

Laboratory task

5.1 Research the counter. Establish a correspondence between governments, shown on the front panel of the device and the structural scheme (pic 1).

5.2 To make the external research of EFC in self-control mode.

5.3 To make research in all work modes.

5.4 In frequency measurement mode perform validation of feature selection on the frequencies given in table 1 (appendix A). The results show in table 5.1.

 

Table 5.1 – Basic characteristics evaluation in “FREQUENCY MEASURMENT” mode.

ƒs, kHz	Тcount, ms	Result, kHz	∆ N, Hz	N	δ N

 

5.5 In period measurement mode perform the same measuring. The results show in table 5.2.

 

Table 5.2 – Basic characteristics evaluation in “PERIOD MEASURMENT” mode.

ƒs, kHz	n	Т м	Result (ms, µs)	∆ N	N	δ N	Тcount, ms

 

5.6 In frequencies ratio mode perform the same measuring. The results show in table 5.3.

 

 

Table 5.3 – Basic characteristics evaluation in “FREQUENCIES RATIO” mode.

ƒ1/ƒ2	n	Result	∆ N	N	δ N	Тcount, ms

 

6. Protocol of the laboratory work (№.... name...)

6.1 The purpose of the experiment.

6.2 List of equipment used in the Table. 6.1.

 

Table 6.1 - List of equipment used

Name of the device	type	serial number	Metrological characteristics
Accuracy	Range	Frequency

 

6.3 Measuring chart.

6.4 To build in one system of coordinates of graphic arts of dependence of relative error of δ _N from frequency in the mode of measuring of frequency and period. To draw a conclusion about the choice of the mode of operations of EFC.

 

 

LABORATORY WORK №7a