extremely accurate digital clock

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how could i get an extremely accurate digital clock . i made a clock with ds1307 but the time is not that much accurate .
 

The accuracy of your system depends on how good your main time base is. In the case of DS1307 it depends on whether you have chosen a proper crystal for your chip, and its capacitive loading.

see this note for details --
**broken link removed**

Of course your measurement method for the accuracy should also be very good. How are you testing the accuracy ?
 

in my clock with ds1307 there is a change of 10min in one week .
it may be because that my clock is placed in a room where machines are working .
 

tpetar said:
I think 10min is too much per week. In what temperature ranges you use this device (room temp, -20C +30C +50C 0C)?
Click to expand...

the room temperate will be 20c to 25c

- - - Updated - - -

is there any other chip which is more better than ds1307
 

getavinks@gmail.com said:
in my clock with ds1307 there is a change of 10min in one week .
it may be because that my clock is placed in a room where machines are working .
Click to expand...

is your change an increase or a decrease ? does it go faster or slower ?
you can improve the accuracy using guidelines from AppNote 58, or go the easier route and use ds3231

it all depends on what you mean by extremely accurate
 

getavinks@gmail.com said:
extremely accurate means the time must be proper for around 6 months.
how is this ds 3231
Click to expand...

upto 60 seconds in 6 months means accuracy/ stability of ~4 ppm. DS3231 datasheet claims to be able to do better than this with proper care in all matters.
i do not have personal experience with this ic however
 

getavinks@gmail.com said:
in my clock with ds1307 there is a change of 10min in one week .
it may be because that my clock is placed in a room where machines are working .
Click to expand...

This suggests you have access to mains AC. Is it reliable enough that you could use it as a timebase? Divide down 50 Hz (or 60 Hz) to get 1 Hz pulses, etc.
 

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