Test clock crystal for drift in a temperature and humidity clock (HTC-1)

[Pha5e]

I have a desk top Temperature and Humidity clock (see photo below). The time seems to advance over a couple of months after being set.

How can I check if it's the crystal or the capacitors connected to the crystal that are causing the drift?

 

[betwixt]

It almost certainly is the crystal or it's loading capacitors but a few seconds drift per month would be quite normal for equipment like that.

If you need absolute precision you need an external clock locked to GPS or a time standard. If you want to try to tweak the existing clock to be more accurate, replace one of the crystal loading capacitors with an adjustable one and set it for better accuracy. You can do this by trial and error although it could take a long time to confirm you have it right or you could use a precision frequency counter to confirm the frequency is correct.

Brian.