Key features

2.1 Modern EFC based on micro processing schemes with hard logic are the multifunctional devices. The transition from one function to another is implemented by installed software or by switching keys.

Functional scheme is shown on pic. 1 relate to EFC with hard logic.

2.2 “FREQUENCY MEASURMENT” mode perform the direct comparing of researched signal frequency with standard frequency value (quartz-crystal generator). Here that gives opportunity to find with digital method the number that will show in how many times bigger than .

On pic. 2 are shown the diagrams of EFC voltages that reveal the point of digital method – the calculation of pulses quantity N coming on counting block (11) during time – “MEASURING TIME” or “COUNTING TIME”.

From diagram follows that the actual value of researched signal frequency equal to:

 

.

 

Measuring of researched signal frequency value:

 

.

 

The value of absolute error of discreteness:

 

 

The maximum value of relative error of discreetness defined by next formula:

 

where, N – quantity of pulses that comes on the counting block of EFC during counting time.

Total error of frequency measuring:

 

 

where – error component causing by quartz-crystal generator.

 

2.3 “PERIOD MEASURMENT” mode perform comparing of researched signal period with standard time interval. Diagrams of EFC voltages are shown on pic. 3. We can see from diagrams that actual value of researched signal period is defined by:

 

 

where – period of standard (master) signal;

N – marks quantity that comes on counting block;

n – period factor.

Counting time is defined by:

 

 

The measuring period value of researched signal:

 

 

The values of relative and absolute error of discreetness are equal to:

 

 

where

Total relative error of measuring:

 

 

where – transformation error caused by ratio of signal/obstacle voltage.

 

2.4 In “FREQUENCIES RATIO” mode the voltage with high frequency (the position of key on switch “1”) is applied on the input “1” (pic.1). In channel 1 this voltage transforms in sequence of short pulses with repetition rate. This pulses comes on the first input of time selector while on the second input is applied the control pulse with duration . Formation of control pulse is performed in channel “2” from the signal with lower frequency applied on the input “2”.

 

From pic. 4 follows equality:

 

 

The actual value of frequency ratio equal to:

 

 

The measuring value of frequencies ratio:

 

 

Counting time:

 

 

The absolute error of discreetness:

 

 

The relative error of discreetness:

 

 

Where

 

Total error of measurement: