Electrical – Crystal marking

While I haven't seen anything with that exact marking, I speculate that it is perhaps a cylinder type 8.000 MHz crystal oscillator, more or less interchangeable with the 8.000 MHz AB308-8.000MHZ, MCRJ308000F18300HZH, ECS-80-18-10X, etc.

I speculate that the S80003H is perhaps exactly the part model as the S80009F, but manufactured in a different week. And so with exactly the same part number except for the date code.

If, hypothetically, this company uses International Rectifier's date code system, then

• "3H" indicates the 8th week of 2003 or 2013, and
• "9F" indicates the 6th week of 1999 or 2009.

From the nRF52832 data sheet:

The easiest is to pulse or toggle a GPIO pin on every TICK interrupt and measure the frequency on your oscilloscope, or even better, compare with a known accurate frequency source. Also, modern PC sound cards can sample 32 kHz, and they are surprisingly accurate, especially when calibrated.

Alternatively, write out the RTC value over the serial port or Bluetooth. Capture the RTC values overnight using a terminal program that has timestamping capability (e.g. Tera Term). After a good night's sleep, your measurement error should be in the 5 ppm region. Don't forget your PC clock drifts too.

Finally, make absolutely sure that you are using two NP0 capacitors on your crystal, and that they conform to the crystal manufacturer's specified value, taking into account the parasitic capacitances of pins and traces.