Siemens SIMATIC S7-300 FM 350-1 - Speed Measurement Mode

Operating Modes, parameters and commands
7.4 Measuring modes
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
143
7.4.4 Speed capture
Speed measurement
In the RPM measurement operating mode, the FM 350-1 counts the pulses that are received
from a tacho-generator within a dynamic measuring time, and calculates the speed from this
value with the number of pulses per encoder revolution.
For the RPM measurement mode, you must also set the pulses per encoder revolution.
This returns the speed expressed in units of 1x10
-3
/min.
8SGDWHWLPH
8SGDWHWLPH
&RXQWSXOVHV
,QWHUQDOJDWH
6WDUWRI530
PHDVXUHPHQW
(QGRI530
PHDVXUHPHQW
Figure 7-33 RPM Measurement with Gate Function
Update Time
The FM 350-1 updates the measured values cyclically. You enable the update time by
means of the "Update time" parameter. You can change the update time during operation.
Table 7- 35 Calculating the Update Time
Value range of n
Boundary conditions Update time
n
min
n
max
Non-isochronous mode Any T
DP
n × 10 ms 1 1000
T
DP
< 10 ms n × T
DP
(10 ms/T
DP
[ms] ) +1
1)
1000 Isochronous mode
T
DP
≥ 10 ms n × T
DP
1 10000 ms/T
DP
[ms]
1)
1
The decimal places obtained after division by T
DP
are omitted.
It is prohibited to exceed these limits. If these limits are exceeded, the FM 350-1 generates a parameterization error and
does not switch to isochronous mode.