I used pulsar detection techniques to turn a phone into a watch timegrapher • Hacker News Board

Re: I used pulsar detection techniques to turn a phone into a watch timegrapher

#31

Post by fecal_henge » Tue, Mar 10, 2026, 10:55 PM UTC

tylerjaywood wrote: post #2

I built an audio timegrapher feature for my watch accuracy app, ChronoLog. Professional timegraphers use a piezo contact sensor and can cost upwards of $1,000. I wanted to do it with a phone mic. The problem: an iPhone's built-in microphone picks up a mechanical watch's tick at about 1.5 dB SNR. The solution turned out to be epoch folding — the same technique radio astronomers use to find pulsars. Stack 100+ tick per…

10 seconds per day is a little over 115 ppm. What is the frequency error of the reference clock that ultimately drives the ADC connected to the microphone?

Re: I used pulsar detection techniques to turn a phone into a watch timegrapher

#32

Post by TApplencourt » Wed, Mar 11, 2026, 2:47 AM UTC

tylerjaywood wrote: post #20

TApplencourt wrote: post #3

Earlier quoted context omitted.

How does it compare to other apps ("watch accuracy meter" for example) on android?

I have this in open beta on Android right now so you're welcome to give it a shot and let me know :) One difference is cost. I know that mine is lower cost, and is a one time unlock -- no subscription. So there's that. I'm also therefore positioned a little bit more towards the casual user, I prioritize speed of completion which means I need high confidence in a good signal quickly and don't hesitate to cancel mid-fl…

>One difference is cost. I know that mine is lower cost, and is a one time unlock

The one I'm talking about is free, so not sure about that. Not sure if I will pay for beta testing : )

Re: I used pulsar detection techniques to turn a phone into a watch timegrapher

#33

Post by syntaxing » Wed, Mar 11, 2026, 3:38 AM UTC

Wow I’m a watch guy and this was a fun read. I used a couple of similar apps and they work ok. I wonder how yours stack up. You can get these cheap piezo ones for $150 but unsure how those perform either.

Re: I used pulsar detection techniques to turn a phone into a watch timegrapher

#34

Post by matheusmoreira » Thu, Mar 12, 2026, 2:38 AM UTC

coredog64 wrote: post #15

matheusmoreira wrote: post #12

Earlier quoted context omitted.

It tells you for how long the time displayed by the watch is valid. If a watch loses ten seconds per day, in a month it will be about five minutes off. The objective is to minimize this number as much as possible. The open source sensor watch has a temperature sensor and software which turns it into a temperature compensated quartz watch. Mine loses time every year instead of every day or every month.

Practically speaking, unless you only own a single mechanical watch you really only care about the per day loss.

Are there reasons to worry about the accuracy of a watch one is not actively using?