[time-nuts] Using speaker / earphone for PPS testing (not a question)

[Chris Burford]

I reached out to SRS several months ago to inquire if the pulse width could be configured from the default of 10 micro second. Their responses was no.

Chris

-----Original Message-----
From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of Taka Kamiya via time-nuts
Sent: Monday, April 20, 2020 22:35
To: Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>
Cc: Taka Kamiya <tkamiya9 at yahoo.com>
Subject: Re: [time-nuts] Using speaker / earphone for PPS testing (not a question)

Out of all signal source, the shortest 1 pps is PRS-10 at 10 micro second.  T-bolt is quite short as well but I don't have a definite data.
For those, speaker method worked just fine.  I'm just sharing what I learned on happenstance.  

--------------------------------------- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

    On Monday, April 20, 2020, 11:05:02 PM EDT, Bill Byrom <time at radio.sent.com> wrote:  
 
 It's easy to trigger on short pulses on most oscilloscopes if you follow these steps:
(1) Do NOT use Auto Trigger mode. Instead use Normal trigger mode.
(2) Set the vertical coupling mode to DC.
(3) Set the vertical gain (volts/div) and offset so that the baseline (OFF voltage between pulses) and pulse ON voltage should both be visible on the vertical scale. 
(4) Set the trigger coupling mode to DC and the trigger source to the proper channel.
(5) Set the trigger voltage to the midpoint between the pulse OFF and ON voltage. 
(6) Set the trigger slope appropriately, depending on the polarity of the 1 PPS pulse.
(7) Many oscilloscopes have a trigger indicator LED. It should flash visibly on each 1 PPS signal.
(8) If you are using an analog scope which does NOT have a microchannel plate (which was used on the Tektronix 2467 family and a few other models), the pulse ON signal may be difficult to see at a fast time/div setting, even with a high scope intensity setting. But you can slow down the time/div of an analog scope to something easy to see, such as 10 ms/div. This will allow you to see a bright sweep each time the scope triggers, even if a short pulse can't be seen.
(9) When using a digital oscilloscope, turn on the peak detect display mode. This allows the oscilloscope to keep a high sampling rate even if the time/div is set for a moderately slow sweep.

If the 1 PPS signal is very short, you won't be able to hear it on a speaker with a direct connection as you describe. But you can use a pulse stretcher circuit (such as a 555 timer IC) to drive a LED or speaker with a long output pulse (such as 10 ms). If you use two 555 IC's (or a 556 dual timer IC), you can even configure one section as a one-shot and the other as a tone generator so that a beep is produced for each pulse. The 555 and 556 may be sold as  LM555/LM556 or NE555/NE556.
--
Bill Byrom N5BB
Retired Tektronix Application Engineer

On Mon, Apr 20, 2020, at 9:25 PM, Taka Kamiya via time-nuts wrote:
> Maybe everyone but I knew, but I just did this and found it useful.
> 1 pps signal from some GPS are notoriously narrow and difficult to sync 
> on and see on scopes.  LED will barely light if some kind of stretcher 
> is not used.  If your purpose is ONLY to see if it's there or not, hook 
> up a small speaker, earphone, amplified or not, and you can hear the 
> tick-tick sound.  
> 
> I like DIYing and many times, I wonder if pps distribution circuit is 
> working.  I can tell a very short pulse that will barely register on 
> LED is clearly audible.
> I thought I'd share.
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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