svorkoetter

WOS does adjust the gain automatically unless you've selected "Adjust threshold level manually" in the "Settings" window.

I want to let everyone know that I've tested a third-party watch test stand with Watch-O-Scope, and it works great! You can get one from AliExpress, the price is extremely reasonable, and you don't need to build your own microphone and amplifier. I've written up the details on the Watch-O-Scope website: http://www.watchoscope.com/teststand.html Also, we've fixed a problem in the Long Term test mode in Watch-O-Scope, so it no longer stops after 13.5 hours. All registered users can download the free upgrade.

Indeed, the piezos that I used when originally developing Watch-O-Scope uses piezos taken out of a greeting card's speaker as their microphones.

What I find interesting is to ask questions about the circuit with only a circuit board layout instead of an actual schematic.

You quoted my entire original post from 6 years ago, pictures and all, to add this (incorrect) bit of information?!? Hint: I've been a professional software developer for 31 years. https://lmgtfy.com/?q=featuritis

Hi @MatteoB, this forum probably isn't the place to get into such details, but very briefly, the input is first filtered (if filtering is enabled) using a 4th order infinite impulse response bandpass filter. After that, the software tracks an envelope of the signal, looking for the three distinct sounds making up each tick (as mentioned by @guidovelasquez). The time of the start of each sound is recorded, and the watch performance computed from those. Statistical analysis is applied to all the ticks within the averaging period. This, together with the initial filtering, is what produces stable results even when the signal is noisy. FFTs are not used.

There's a big difference between a preamp and a headphone amp. In the simplest terms, a preamp takes a very weak signal (or in the case of a watch mic, a very very very weak signal) and turns it into just a weak signal. A headphone amp turns a weak signal into a strong signal. Amplifiers also do impedance matching. A piezo element's impedance is primarily capacitive (around 27pF for the one I use), whereas a sound card's input impedance is resistive, typically around 10kΩ. A suitable preamp has corresponding input and output impedances. A headphone amplifier on the other hand takes a signal with about a 10kΩ impedance and converts it to a stronger signal with a much lower impedance, typically around 8Ω to 32Ω. Thus, a preamp is primarily a voltage amplifier to boost a weak signal, and a headphone amp is primarily a current amplifier to drive the low impedance of the headphones. The Schiit amp you mention has a selectable voltage gain of 0dB or 5.5dB (1x to 1.8x). The amplifier used by Watch-O-Scope has a gain 75dB (about 5600x). So they're not at all similar.

Yes, you can just download the new version and it will update your installed version without messing up your license.

Hi All ... I just wanted to let you know that I've just released Watch-O-Scope 1.3, with the following improvements and new features: Built-in volume boost, adjustable via scope and manual adjustment modes, requiring less external amplification. Long term test improvements: Ignore extreme outliers (±4σ) for better immunity to non-timekeeping noises (e.g. the date wheel clicking over at midnight, doors slamming, cars crashing outside). Clip graphs to three standard deviations (±3σ). Highlight one standard deviation (±σ). Support for manually selected beat rates all the way down to 300 bph. Report weights for standard positions are remembered and become the defaults for subsequent reports.

So far, the kit that Eland posted seems to be a good option for someone who doesn't want to start from scratch. I will pick one up when I'm in Germany later this month, and give it a try. The thing I like about it is that it doesn't use a proprietary part. The LF351 is generic, has multiple sources, and has been around for a long time. I just haven't had any experience with it before now.

Yes, so long as neither the input (not likely) nor output signal is more than about 2V peak-to-peak.

The gain of that circuit is only about 100 (40dB), which probably won't be adequate, and despite what the manual says, it won't run off of 3V. At 3V, the input signal is biased at 1.5V, which is of course only 1.5V below the chip's supply voltage, a point above which it will not operate. Put another way, there is zero headroom if operated at 3V. The only thing it will amplify without severe distortion is total silence.

Unlike a capacitor microphone, a piezo doesn't need a power source. And a dynamic microphone is a power source.

I agree with JerseyMo in principle, but of course those aren't the rules here. However, I don't see how buying a cheap knockoff piece could be "too cheap". You have a cheap knockoff watch, so why would that be any different than the original missing piece? A real Rolex piece would indeed be expensive, they won't sell you one anyway, and it probably wouldn't fit.