Omron CJ1M-CPU21, Operation Manual

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COUNTER FREQUENCY CONVERT: PRV2(883) Section 5-3
• Counter input method: 4
×
differential phase mode
Conversion result = 00000000 to 00030D40 hex (0 to 200,000)
(If a frequency higher than 200 kHz has been input, the output will re-
main at the maximum value of 00030D40 hex.)
2. Frequency Calculation Method
When the CPU Unit is a CJ1M CPU Unit with version number 3.0 or later,
there are two ways to calculate the frequency of pulses input to high-speed
counter 0.
a) Standard Calculation Method (Earlier Method)
When C1 = 0 @ 00, the count is calculated by counting each pulse re-
gardless of the frequency. At high frequencies, the rising or falling edg-
es of some pulses will be corrupted, resulting in errors (about 1% error
max. at 100 kHz).
b) High-frequency Calculation Method
In this case, the counting method is switched at high and low frequen-
cies. (Supported by CJM1 CPU Unit Ver. 3.0 or later only)
• High-frequency counting
At high frequencies (above 1 kHz), the function counts the number of
pulses within a fixed interval (the sampling time) and calculates the fre-
quency from that count. One of the following three sampling times can
be selected by the third digit of C1.
• Low-frequency counting
At frequencies below 1 kHz, the Standard Calculation Method is used,
regardless of the sampling time setting.
Converting Counter PV to Total Number of Revolutions (C1 = 0001 hex)
If C1 is 0001 hex, PRV2(883) calculates the cumulative number of revolutions
from the counter PV and pulses/revolution setting.
Conversion result = Counter PV
÷
Pulses/revolution
Flags
Sampling time Value of C1 Description
10 ms 0 @ 10 hex Counts the number of pulses every 10 ms.
The error is 10% max. at 1 kHz.
100 ms 0 @ 20 hex Counts the number of pulses every 100 ms.
The error is 1% max. at 1 kHz.
1 s 0 @ 30 hex Counts the number of pulses every 1 s. The
error is 0.1% max. at 1 kHz.
Name Label Operation
Error Flag ER ON if high-speed counter 0 is disabled in the settings.
ON if C1 is not in a specified value (0000 or 0001).
ON if the pulses/revolution setting in C2 is 0000.