Mitsubishi MELSEC QS Series User Manual page 186

9
DEVICE EXPLANATION
(6) Retentive timers
9
- 20 9.2 Internal User Devices
9.2.8 Timer (T)
(a) Definition
Retentive timers measure the "coil ON" time.
The measurement begins when the timer coil switches ON, and the contact
switches ON when a time-out (coil OFF) occurs.
Even when the timer coil is OFF, the current value and the contact ON/OFF status
are saved. When the coil is switched ON again, the time measurement resumes
from the current value which was saved.
(b) Retentive timer types
There are 2 retentive timer types: low speed retentive timer, and high speed
retentive timer.
(c) Retentive timer clear
The RST ST instruction is used to clear (reset) the current value and switch the
contact OFF.
[Ladder example]
X100
X102
[Time chart]
X100
ST0 coil
ST0 present value
ST0 contact
RST ST0 instruction
X102
Diagram 9.20 Ladder example and timing chart of retentive timer
(d) Measurement units
The measurement units settings for retentive timers are the same as those for low
speed timers and high speed timers.
• Low speed retentive timer : Same as low speed timer
• High speed retentive timer : Same as high speed timer
POINT
In order to use retentive timers, a retentive timer "number of points used" setting
must be designated at the "Device" tab screen in the "(PLC) Parameter" dialog
box.
K200
ST0
RST ST0
ON
OFF
ON
OFF
15s
to
0 1
Present value is saved
when coil switches.
OFF
Contact remains ON when coil switches.
OFF
X100 ON time is measured as 20 seconds
when the timer measures time in 100 ms units.
Retentive timer display
When X102 switches ON, the ST0 contact is
reset, and the current value is cleared.
5s
150 151 to 200
ON
Instruction execution
0
ON