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Economist
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Gated vs Triggered

07/16/2011 1:32 PM

I have a function generator by global specialties 2003 model.

Two modes are available to used, gated and triggered. I want to turn it on using a TTL signal supplied from an external source.

When I used triggered, it only turns on the rising edge.

When I used gated, it does not work.

What I want is for my function generator to turn on when my signal is on and vice versa.

Any ideas.

Thanks

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redfred
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#1

Re: Gated vs Triggered

07/16/2011 2:22 PM

I looked for the 2003 model but could only find the 2001A model to try and find some more information. So my only advice is the obvious ones. Maybe your test instrument is actually broken. (I know that this is not helpful but I'm trying to be thorough. ) Maybe there's a hidden gate threshold adjustment that needs to be set. Maybe the gate function is working fine but you are just not using it properly or that it works differently than you expect. (Again being thorough, but without a manual to refer to...)

Maybe your best bet would be to build a separate circuit that gates your continuous function generator signal. You can do this very easily with a FET switch and a buffering op-amp.

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Mikerho
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#2
In reply to #1

Re: Gated vs Triggered

07/16/2011 5:28 PM

Hi redfred,

I have seen your posts here and have a lot of respect for your ability as an EE.

I want to build a function generator and have found this:

Do you think this is a valid design? Are the outputs of the 74HC14 just supposed to float?

I have tried to make the schematic bigger, but to no avail. The original sch is here.

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#3
In reply to #2

Re: Gated vs Triggered

07/16/2011 5:35 PM

Please start a new post.

here is a spec sheet for the model 2003.

http://www.eurekaspot.com/webdata/mfr_pdfs/GS/GS(2003.pdf

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Mikerho
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#4
In reply to #3

Re: Gated vs Triggered

07/16/2011 5:43 PM

Sorry, I forgot to post OT. However, someone else may benefit from redfred's answer to me.; and why is this a problem?

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JohnDG
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#6
In reply to #3

Re: Gated vs Triggered

07/16/2011 6:19 PM

This is only a short-form spec. Can you give a link to a user manual (or whatever) with full spec? Should include input logic levels etc.

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JohnDG
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#5
In reply to #2

Re: Gated vs Triggered

07/16/2011 6:11 PM

Crap system on CR4 - no chance of posting decent cct diagrams. Is it on-line anywhere, so you could give a link to it? Or maybe you could upload it somewhere and link it?

[OP does have a point, tho', you could've started a new thread or pm'd redfred (OP feels hijacked - and maybe justifiably)]

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#7
In reply to #5

Re: Gated vs Triggered

07/16/2011 6:57 PM

So my real question should be does anyone have the spec on a general specialties model 2003 function generator.

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#8
In reply to #7

Re: Gated vs Triggered

07/16/2011 7:04 PM

Just to fill us in, why don't you have the original docs?

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#9
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Re: Gated vs Triggered

07/16/2011 7:27 PM

I can't find them.

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#13
In reply to #9

Re: Gated vs Triggered

07/16/2011 9:25 PM

Happens all the time. Unfortunately without knowing what the original design intent of the gating function, it is difficult to say what the gate conditions and function should be. Contact the original manufacturer for a PDF file or just a clarification.

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#10
In reply to #2

Re: Gated vs Triggered

07/16/2011 7:30 PM

Gee, I'm truly flattered. Thank you very much.

I'll try to keep this brief because our OP is correct that this is a hijacking of their original topic. (Although you are asking for a way to build your own generator.) Even your original schematic link is too fuzzy for my laptop and and best reading glasses. It looks this design is a microcontroller based function generator with a buffered D/A. This approach is likely what the 2003 our OP is doing. This does mean though that you will have to write or acquire the appropriate code. The only thing that I'd change from what I see here is that I'd include a ±15V supply somewhere so that the output could get a larger swing than the ±4.5V this circuit will produce.

If you post a new thread with a link to a clearer schematic I'll gladly add any new comments there. Who knows maybe you can get a few comments from Winfield Hill, now there's a sharp Engineer.

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#12
In reply to #2

Re: Gated vs Triggered

07/16/2011 7:56 PM

"... Are the outputs of the 74HC14 just supposed to float?"

Just to clear this up - I assume you're referring to the 4 inverters bottom r.h. corner.

These are drawn in just for completeness - they are the unused parts of the 74HC14 (hex inverting Schmitt trigger) package. The outputs aren't 'floating' - their inputs are at a defined state (0V).

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#14
In reply to #12

Re: Gated vs Triggered

07/16/2011 9:38 PM

Just to clear this up - I assume you're referring to the 4 inverters bottom r.h. corner.

These are drawn in just for completeness - they are the unused parts of the 74HC14 (hex inverting Schmitt trigger) package.

I knew that. However, I have seen unused pins on ICs that needed to be grounded or other somesuch.

I guess in this case, since the individual inverters are electrically separate, it wouldn't matter. Duh!

Thanks!

I learn more every day...

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#11

Re: Gated vs Triggered

07/16/2011 7:45 PM

Hi Economist,

I want to apologise for posting my own question here. Being that I'm developing a function generator myself, I jumped when the trigger (your thread) presented itself.

Sorry,

Mike

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