external crystal oscillator in RTC

[KPITSENTHI]

I am using 20 PPM external crystal oscillator in RTC because of 20 PPM it shell be give 1.33 sec delay per day how can I calculate the error in this external crystal.

 

[betwixt]

There are 86,400 seconds in one day so the error is 1.33 in 86,400. Work out the % error and apply it to the oscillator. Without knowing the frequencies involved it's difficult to give more advice. An error as small as that can normally be controlled by adjusting capacitors around the crystal.

Brian.

 

[KPITSENTHI]

I am not getting what is 86,400 can you please explain bit brief

Added after 35 seconds:

I am not getting what is 86,400 can you please explain bit brief

Can you please let me the formula for calculate error?

 

[keith1200rs]

60 seconds in a minute, 60 minutes in an hour, 24 hours in a day. So number of seconds in a day is 60x60x24 = 86400.

Your error is 1.33 in 86400 = 1.33/86400 = 15e-6 or 15ppm.

Keith.

 

[KPITSENTHI]

Actual frequency = 32768 (Hz)

20 ppm frequency =32768-20 = 32748

Actual frequency per day = 32768 * 3600 * 24 = 2831155200

20 ppm error frequency per day = 32748* 3600 * 24 = 2829427200


Error frequency per day = 2831155200 – 2831068800 = 1728000 Hz /per day


frequency = 1728000 /1000000 = 1.74 sec

20 PPM error in 32.768 Khz. crystal oscillator = 0.5 Sec per day


Pelase let me know my caluation is right or worng

 

[FvM]

keith1200rs has shown the correct calculation in one line. Your result is wrong.

 

[keith1200rs]

20 ppm frequency =32768-20 = 32748


Pelase let me know my caluation is right or worng

This is wrong. 20ppm is 20 parts per million. You have used 20Hz here.

Keith.