Appendix 5 common question A&Q
Appendix 5 common question A&Q
The following are the common questions may happen when using the PLC.
Q1：why the coil is not set when the condition is satisfied?
A1：the probable reasons:
（1）use one coil for many times, double coils output, the later coil has priority.
（2）some conditions reset the coil, please use monitor function to find the reset point and
modify the program.
Q2： set on the pulse output instruction, the pulse doesn’t output?
A2：there are many pulse output instructions in the program.
Q3：why connect the high speed counter but no counter value?
A3：the probable reasons:
（1）make sure the PLC has high speed counter photo-couplers.
（2）when the PLC hardware version is 2.5 and software version is 3.0, it is not available to
use HSC, please update the hardware version to 3.0.
Q4：What’s the difference between com1 and com2?
A4：the communication parameters of com1 and com2 can set by users. The difference is com1
can return to default parameters by stop PLC after power on.
Q5：Why free format communication is failure?
A5：check the communication parameters, if use com2, please set the FD8220 to HFF, FD8221 set
to corresponding parameters.
Q6：why the real time clock(RTC) can not work?
A6：XC3-14 and XP1 do not have RTC function.
Q7：why PLC can not communicate with other device?
A7：the probable reasons:
（1）communication parameters: PLC com port and device parameters must be the same.
（2）communication cable: connection correct and good.
（3）communication serial port: check the serial port, download the PLC program, if
download successful the serial port is no problem.
（4）ask manufacturer for help.
Q8：how long can the PLC battery be used?
A8：for 3-5 years.
Q9：why the temperature fluctuates serious under normal temperature when connecting the
thermocouple with the temperature module?
A9：the probable reasons:
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