Mitsubishi Electric MELSEC-L02SCPU User Manual page 224

(4) Measurement example
In this example, frequency is measured under the following conditions.
• Actual frequency: 1234Hz
• Frequency measurement unit time: 0.01s
• Frequency movement averaging processing count: 1 (The moving average processing is not performed.)
(a) Count value per time unit
Count value per time unit for the actual frequency is calculated as follows using the formula in ( Page 221,
Section 8.5 (1) (b)).
The count value should be an integer. For this reason, the count value in this example is 12 or 13 because the
numbers after the decimal point is accumulated within the module. When this count value is used in the formula
above, the following result can be acquired.
(b) Calculating frequency error (maximum)
222
1234(Hz)
=
Count value per unit time
Frequency measurement value (Hz)
Frequency measurement value (Hz) =
Error (maximum) (Hz) = 1234(Hz)
= 0.07404(Hz) + 100(Hz)
= 100.07404(Hz)
Count value per unit time
0.01(s)
=
12.34
12 or 13
=
0.01(s)
1200(Hz) or 1300(Hz)
60(ppm)
+
1000000 0.01(s)
1
1