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

[Bob kb8tq]

Hi

One of the simplest justifications I can think of for a dirt cheap “Chinese” 
digital ’scope is to capture short burst stuff like narrow pps pulses. 

10 us / non-adjustable is a *very* common spec for a 1 PPS. 

Bob

> On Apr 21, 2020, at 4:56 AM, Chris Burford <cburford1 at austin.rr.com> wrote:
> 
> 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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