How to measure time between two events on an FX3GE?

[Garcia 0]

I have a huge confusion regarding the retentive timers on FX3GE. According to the programming manual for FX3G(image attached), all retentive timers use the EEPROM. This is very confusing to me because the retentive timers are modifying the measured time constantly in an EEPROM register and EEPROM type of memory is known to be write limited. After a couple of million write cycles the EEPROM registers burnout. I've experienced this myself by constantly using the T250 and after a while it became unusable. The timer stopped counting time after some time.

This leads to my decision that retentive timers on FX3GE PLCs are something that should бе used only on rare occasions so as to avoid EEPROM memory burnout. If this is true than the real question comes in: What is an alternative for using retentive timers on FX3GE when you want to measure time between two events. The instruction TTMR for teaching timer is appropriate however this instruction does not exist on FX3G series.

 

[Nightfly 12]

Depends how accurate you want it, but you could always periodically simply increment a DINT. Have one that counts up every second (no need to reset as it’s good for over 60 years). When something starts, copy the value of the DINT to a “start time” Register, same when it stops. The time in seconds is obviously stop time – start time.

[Garcia 0]

Quote

Depends how accurate you want it, but you could always periodically simply increment a DINT. Have one that counts up every second (no need to reset as it’s good for over 60 years). When something starts, copy the value of the DINT to a “start time” Register, same when it stops. The time in seconds is obviously stop time – start time.

Seems a bit hacky but I guess it's better than nothing. I am surprised that Mitsubishi would not think of this. Thanks for the suggestion.

Edited 11 Dec 2021 by Garcia