RTC to milliseconds

[Alan73922]

@Mark105601

then move them under their independent battery power into various positions on the gear for the testing.

I see your constraint now - battery power and portable. Today you might use a WiFi system to distribute a time signal but I gather you are talking a few years ago when that was infeasible/too expensive/used too much power.

@Mark105601

primarily to avoid making adjustments in a cluster

I don’t understand what this means. I didn’t flesh out the method completely, there are buffering requirements to prevent glitches. One use is to dither a 10 bit PWM at 40kHz, after filtering it is equivalent to a 24 bit DAC as long as the voltage isn’t required to change quickly. Works well.

[Mark105601]

@Alan73922

I see your constraint now - battery power and portable. Today you might use a WiFi system to distribute a time signal but I gather you are talking a few years ago when that was infeasible/too expensive/used too much power.

Yes, WiFi wasn’t an option either in an EM noisy, high voltage and multi-storey environment. I doubt that WiFi systems even today would be able to cope.

@Alan73922

@Mark105601

primarily to avoid making adjustments in a cluster

I don’t understand what this means.

I recall that our calibration values required up to 30 RTC clocks (worst case) to be adjusted to achieve accuracy for a given crystal. We spread the adjustments over a range of seconds so we didn’t try to add or subtract 30 RTC clocks from the clock in one hit, which would have compromised our results.