# Modern Test Equipment



## Silver Hawk (Dec 2, 2003)

Someone emailed me a few weeks ago asking if I knew the output voltage of an old Accutron Test Meter when it was set to "Low Amplitude" 

I had no idea; I do have an Accutron Test Meter (700 Series) that I bought from Roy many years ago, but I rarely use it and have never measured the output voltage in this setting. But my interest was piqued, so an email dialogue ensued and it turned out that "John" (real name withheld to protect the innocent) had made a modern test meter and the photo of it looked really impressive.

To cut a long story short, I did some work for him on some of his Accutrons and John's test meter is now mine  --- he didn't mind, since he is now working on his Mark 2 version. So today I played with it a bit and also compared it with the original Accutron test meter; took a few photos as well







.

First photo shows the dummy battery installed in a Cal. 2181 Accutron still in its watch case. This little device is part of the original Accutron Test Kit:










Next, the original Accutron Test Meter Series 700 in action. The 2181 Accutron is connected up and a battery is installed under the clip in the centre of the meter. This is supplying power to the watch via the meter. With the switch set to "Low Amplitude", the watch is drawing about 8 micro-amperes --- a correct figure for this calibre.










Now the modern meter. Built from parts from Maplins, the meter on the left shows micro-amperes while the LCD display on the right shows the current voltage setting (1.554v)....voltage can be adjusted between 0 and 2v using the dial below the LCD panel. Being a cheapish Chinese LCD panel, it draws quite a lot of current itself, which is why the ammeter is showing 15 micro-amperes with nothing connected:










The big toggle switch in the centre isolates this LCD panel once the voltage has been set, so the ammeter now shows zero with nothing connected:










The last picture is the modern meter in action. The voltage was set to 1.554v, the LCD panel isolated and the 2181 movement is drawing about 9 micro-amperes...which is bang on what Bulova recommend and agrees with the markings for a 218 on the old meter dial.

Interestingly, if the tuning fork is not vibrating either because it failed to start on its own or the movement is hacked, the current goes up to about 22 micro-amperes....which suggests to me that your battery is going to run out a lot quicker when you hack this movement  .










So what is the "Low Amplitude" setting on the old meter all about? Well its to ensure the indexing is set up correctly. In this setting, the supplied voltage is no longer 1.5 volts but 1.25 volts. This is still enough to make the tuning fork vibrate but is it vibrating enough to allowing indexing to take place? In this setting, you adjust indexing to ensure it does work at the reduced voltage.

Does the modern meter have any advantages over the old one? Yes, several. The old meter is calibrated to expect the old 1.3 volt mercury batteries, so things are not quite right with a 1.5 volt battery inserted in the clip. And secondly, being able to set the supplied voltage to any value is very useful...you can see very precisely at what voltage index stops, or at what voltage the tuning forks stop vibrating. The modern meter is not just for Accutrons, or even tuning fork watches, but is a useful tool for any battery driven watch.

I look forward to the Mark 2 version "John".


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## jasonm (Nov 22, 2003)

Really interesting post Paul...

Thanks for taking the time to do it :hi:


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## dobra (Aug 20, 2009)

Excellent analysis and report, Paul. As a Space-view owner who hasn't removed the back cover.... Mike


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## Silver Hawk (Dec 2, 2003)

jasonm said:


> Really interesting post Paul...
> 
> Thanks for taking the time to do it :hi:





dobra said:


> Excellent analysis and report, Paul. As a Space-view owner who hasn't removed the back cover.... Mike


Thanks guys...I was beginning to think no-one was interested  .


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## BlueKnight (Oct 29, 2009)

Silver Hawk said:


> jasonm said:
> 
> 
> > Really interesting post Paul...
> ...


Will you try it on my watch?


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## Silver Hawk (Dec 2, 2003)

BlueKnight said:


> Silver Hawk said:
> 
> 
> > jasonm said:
> ...


 :yes:


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## luddite (Dec 11, 2009)

Silver Hawk said:


> Thanks guys...I was beginning to think no-one was interested  .


Rest assured that we were hanging on your every word Paul. :notworthy:


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## mel (Dec 6, 2006)

I reckon a word to "John" is also in order - nice construction job there. One of my "loves" in life at work making prototypes or one-off's of any kind, a great challenge, and yet very satisfying. :yes:

And an improvement for Paul (Silver Hawk) being able to calibrate againstthe more modern batteries! All in all a great job I would say. 

"John", is it <rats nest> inside or a PCB or what? :lookaround:


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## Steve's Dad (Dec 19, 2007)

Silver Hawk said:


> Thanks guys...I was beginning to think no-one was interested  .


It's interesting alright Paul, but I suspect others (like myself) don't have enough knowledge to give an interesting response.

I think we are all just reassured by this kind of stuff that when we send our hummers to you for service/repair, you actually know what you're doing. :thumbsup:


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## JonW (Mar 23, 2005)

Cool! great to see someone making one of these, well done 'John' and Paul


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## louiswu (May 16, 2009)

Silver Hawk said:


> Thanks guys...I was beginning to think no-one was interested  .


Interested ? Yep, definitely :thumbup:

Able to completely understand the elec-trickery involved? Nope :duh:

Thanks for taking the time and effort to share this. My education continues .....


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## louiswu (May 16, 2009)

Silver Hawk said:


> Thanks guys...I was beginning to think no-one was interested  .


Interested ? Yep, definitely :thumbup:

Able to completely understand the elec-trickery involved? Nope :duh:

Thanks for taking the time and effort to share this. My education continues .....


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