I recently got one fo these from ebay for $1.99;
http://www.ebay.com.au/itm/DS3231-A...ck-module-memory-module-Arduino-/400503978923
It uses the DS3231 high accuracy RTC chip.
Unlike the old DS1307 which needed a 32kHz watch xtal, this one has internal oscillator so it doesn't need the xtal, and even better, has precise timekeeping to give <2 PPM precision at room temps.
I used to use the old DS32kHz modules, which were big and clunky (and expensive) to get <2PPM freq output, but this is a complete clock on a chip, that already has the <2PPM precision.
There is a programmable squarewave output pin that can be set at 1 Hz, so I'm thinking this really cheap little chip could be a nice reference clock for a high precision frequency meter project? ie; use it to gate the freq meter at 1 second or 5 second intervals and instantly get better than 2 PPM precision.
http://www.ebay.com.au/itm/DS3231-A...ck-module-memory-module-Arduino-/400503978923
It uses the DS3231 high accuracy RTC chip.
Unlike the old DS1307 which needed a 32kHz watch xtal, this one has internal oscillator so it doesn't need the xtal, and even better, has precise timekeeping to give <2 PPM precision at room temps.
I used to use the old DS32kHz modules, which were big and clunky (and expensive) to get <2PPM freq output, but this is a complete clock on a chip, that already has the <2PPM precision.
There is a programmable squarewave output pin that can be set at 1 Hz, so I'm thinking this really cheap little chip could be a nice reference clock for a high precision frequency meter project? ie; use it to gate the freq meter at 1 second or 5 second intervals and instantly get better than 2 PPM precision.