Re: Amateur FTIR
- From: Sam Goldwasser <sam@xxxxxxxxxxxxxxxxxx>
- Date: 10 Nov 2005 10:52:06 -0500
"Douglas Taylor" <dj.taylor@xxxxxxxxxxxxx> writes:
> "Sam Goldwasser" <sam@xxxxxxxxxxxxxxxxxx> wrote in message
> news:6wk6fhdwjv.fsf@xxxxxxxxxxxxxxxxxxxxx
> > "Douglas Taylor" <dj.taylor@xxxxxxxxxxxxx> writes:
> >
> >> Is it possible to build your own FTIR?
> >>
> >> I don't mean from scratch, I mean is it possible to build one out of
> >> 'parts'.
> >
> > Sure, why not? :)
> >
> >> I ask because I just bought the electronics and beamsplitter/moving
> >> mirror
> >> assembly from a Nicolet Spectrometer. The moving mirror is a 'porch
> >> swing'
> >> type so I don't need air for an air bearing, the KBr beamsplitter looks
> >> in
> >> excellent shape. It would be neat to get this working in a stand-alone
> >> mode.
> >
> > You may be better off ignoring the electronics except maybe the detector
> > front-end and doing your own unless documentation is available.
>
> I have given this some thought.... The electronic functions that are needed
> are:
>
> 1. Amp to drive the mirror motor - sort of a saw tooth drive signal
> (audio freq bandwidth)
> 2. Laser signal phase lock loop - if the mirror moves at a constant
> speed the laser interference signal will be a sine wave in the audio
> spectrum, I think you couple this to the mirror drive to keep the mirror
> speed constant.
So these together form a constant reference frequency drive.
> 3. A/D trigger signal - you use the laser reference zero crossings to
> trigger the A/D
Is that a high enough sampling rate? I guess if it's IR, then the fringe
signal for the unknown spectrum will be a lower frequency but you still
need to obey Mr. Nyquist.
> 4. Start & End of scan - you need to know where the mirror is, either at
> the start of the scan or end and either direct the mirror drive circuit to
> tell the mirror motor to go forward or backward.
> 5. Digital interface - connect the A/D to a computer, monitor other
> signals.
>
> Sounds like a lot of basic electrical circuit stuff, nothing exotic. Maybe
> it is possible to build.
> >> I still need an laser and detector (working on it), but the real question
> >> is can I operate the electronics independently?
> > You mean a laser for the reference?
> Yes, an ordinary HeNe laser is what is used. The beamsplitter I have
> has a small circular area in the middle which is where the laser reference
> beam is directed. I comes out the other side of the interferometer into a
> small detector.
So it sounds like you have an interesting project if you're in it for
the challenge. Even if you don't do the full FTIR, you could build a
nice accurate wavemeter with what you have.
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.
.
- References:
- Amateur FTIR
- From: Douglas Taylor
- Re: Amateur FTIR
- From: Sam Goldwasser
- Re: Amateur FTIR
- From: Douglas Taylor
- Amateur FTIR
- Prev by Date: Re: Amateur FTIR
- Next by Date: Re: Eprom Eraser, how to build
- Previous by thread: Re: Amateur FTIR
- Next by thread: Spectroscopy for home
- Index(es):
Relevant Pages
|
