The approximate resolution of the FV Converter is shown in following diagram.

 

 

When the input frequency is 1500 Hz

 

The clock frequency of the cycle measurement is 20 MHz. The count value of the input frequency can be measured by the following formula;

20000000 ÷ (Input frequency) = Count value
With the input frequency of 1500 Hz: 20000000 ÷ 1500 = 13333.33

The count value is integer, so the resolution of the above formula is 13333 or 13334. By back calculating the count values into the frequency, following values are obtained.

20000000÷13333=1500.0375
20000000÷13334=1499.925

The difference between above formulas is 1500.0375−1499.925=0.1125 Hz

Due to this, it has approx. 0.12 Hz resolution in the input frequency of around 1500 Hz. Note that an error of 0.0375 Hz is occurred to the 1500 Hz measurement. With the consideration of the crystal oscillator accuracy, the 1500 Hz accuracy will be something over 0.12 Hz.

 

In the case of deviation output

 

In the case of deviation output, the resolution is same as the others, but the output voltage per one resolution is larger than others.

 

 

The accuracy of the voltage output of the low frequency

 

Outputs the voltage to which the inverse number of count value is converted by the 16-bit converter

When 1 is entered to each of 16-bit (full) of the binary counter, the frequency is 305.1 Hz.

When the frequency is 305.1 Hz or less, it becomes 16 bit or more. Cut off the lower bit of the binary counter and calculate by upper 16 bits.

The accuracy in this state is;

 

Accuracy = input frequency ÷ 2¹⁵

 

 

The accuracy mentioned in the brochure

Voltage output 0.1 % FS
Current output 0.7 % FS

The resolution and analog circuit accuracy of 20 kHz are mentioned in the brochure because the accuracy of them becomes worst.

 

The input frequency can be modified to the maximum of 50 kHz. The accuracy of this model has same features as the other input frequency.