Varying interval time for PID

[jwscs]

hi every one,

i have to measure ph and control the flow of co2, so i decided to use the helpful PID vis like i do for my temperature control.

the difference and hence my question is, i don't want (/ be able) to run the PID in a timed-loop, in fact my measurement intervals (eg. every ~30s or ~60s) may vary in the second range, because of how i aquire the data and the way i set the co2-valve.

so my question is: is this a non-problem?

i am just not sure wether the internal-timer or supplying the dt explicitly will take care of this?

(and i can not test it on the hardware atm)

thx for your time

[nathand · Accepted solution]

Shouldn't be a problem. Don't wire dt, let the PID use its internal timer. Might make it more difficult to tune the PID since you'll have to account for the worst case (longest possible delay between updates).

[jwscs]

thx, that was what i was hoping for