16F628 Internal clock

I wish to add a frequency counter to a square wave generator (20Hz to 3kHz, TTL) using the COUNT instruction, and to keep it really simple was going to use a 16F628, 8x1 LCD and 100nF decoupling capacitor!

Intended to use the internal oscillator and tweak the count period to get a fairly accurate reading (with 3%?).

But wondered if the internal clock drifted with age, temperature, etc?

Thanks

Yup, that's the bad part. The internal OSC will shift with temperature, wind direction, Gas price and almost everything else. If you need accuracy, use a Crystal.

Thanks. Will just have to had a crystal to the parts list!