Mitsubishi Electric MELSEC-Q Series User Manual page 179

10 DEVICES
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Retentive timers
(1) Definition
(a) Retentive timers measure the "coil ON" time.
(b) 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 present value and the contact
ON/OFF status are saved. When the coil is switched ON again, the time
measurement resumes from the present value which was saved.
(c) There are 2 retentive timer types: low-speed retentive timer, and high-speed
retentive timer.
(d) The RST T
switch the contact OFF.
[Ladder example]
X0
X1
[Time chart]
X0 OFF
T0 coil OFF
T0 present value
Present value is saved when coil switches.
T0 contact OFF
RST ST0 instruction
X1 OFF
(2) Measurement units
(a) 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
REMARK
In order to use retentive timers, a retentive timer "number of points used" setting
must be designated in the PLC parameters device settings.
instruction is used to clear (reset) the present value and
K200
X0 ON time is measured as 20 seconds when the timer
ST0
measures time in 100 ms units.
Retentive timer display
RST ST0 When X1 switches ON, the ST0 contact is reset, and
the present value is cleared.
ON
ON
15 Sec.
0 1 to 150
Contact remains ON when coil switches.
MELSEC-Q
5 Sec.
151 to 200 0
ON
Instruction execution
ON
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