[time-nuts] [Fwd: RE: [Microscope] Re: HR2000 Retuning]

J. Forster jfor at quikus.com
Tue Jan 24 12:35:16 EST 2012


---------------------------- Original Message ----------------------------
Subject: RE: [Microscope] Re: [time-nuts] HR2000 Retuning
From:    "Randall Buck" <rbuck at silcom.com>
Date:    Tue, January 24, 2012 8:35 am
To:      Microscope at yahoogroups.com
--------------------------------------------------------------------------


Possible sources for Hg vapor calibration:

1)  The Penray lamp (a small tube ~ 2" long) with its special ballast is the
standard Hg line calibration source.

2) Ordinary CFL ("spring style" lamps) will give a few HG lines against a
continuum of phosphorescence.  I haven't tried it but it should probably be
sufficient.  Note the relative position of the lines and their wavelengths
before moving the grating.

3) T-5 , miniature 6" or 8" fluorescent lamps are available without an
internal phosphor coating.  These are used in germicidal fixtures and (with
a filter) for geological prospecting.

4) You might be able to find a "germicidal" lamp with a standard light bulb
(Edison thread) base -- the clear glass envelope is a small sphere about 1
1/2 " dia.

5) Backyard pond water sterilizers use an Hg vapor lamp.  I think these
should not be operated for long out of cooling water.


IMPORTANT NOTE:  All HG lamps are capable of emitting potentially dangerous
levels of ultra violet light.  The Penray and germicidal lamps demand
particular caution since they are designed to emit the 254nm Hg line and
even 185nm line -- both wavelengths are in the UVC band.  Shielding, using
aluminum foil with a pinhole for calibration, and UV protection goggles are
essential.  Electric arc welding goggles MAY be appropriate (check first) ,
gas welding goggles are NOT appropriate.

Randall






-----Original Message-----
From: Microscope at yahoogroups.com [mailto:Microscope at yahoogroups.com]On
Behalf Of J. Forster
Sent: Monday, January 23, 2012 5:34 PM
To: nerd at verizon.net; Discussion of precise time and frequency
measurement
Cc: microscope at yahoogroups.com
Subject: [Microscope] Re: [time-nuts] HR2000 Retuning


That about covers it. One note, this preoceedure will move the wavelength
range the unit scans, but will not alter it. To cover a wider chunk of
spectrum, the grating will have to be changed the one with fewer or more
lp/mm.

Also you can look for light leaks by shining a flashlight at the unit
while watching the display,. A light leak will raise the noise floor
across the spectrum.

-John

=================


> My extreme curiosity eventually led me to acquire a couple ofHR2000
> spectrometers from Roland.  He still has several left, and if you ever
> want to
> have the chance to grab one of these, I recommend you act fast.
>
> The units he has were from a medical diagnostic device and have a grating
> which
> gives about 200 nm of range.  The internal sensor is specified to operate
> over
> the range of 200 to 1100 nm.  My units were adjusted to work over the
> range of
> about 467 to 671 nm.  Should you need it, Ocean Optics will gladly (for
> IIRC
> around $500) put a different grating in, or for somewhat less, change the
> range
> of the existing grating.
>
> I needed to be able to cover the wavelength of a Blu-ray laser at around
> 405 nm
> so decided to attempt a recalibration.  I was able to download the manual
> as
> well as their OOIBase32 software which talks to the spectrometer over USB.
>  I
> got a couple of USB adapters so I could plug the units directly into the
> computer's standard ports.
>
> On the side of the unit you will notice a circular slotted pattern with a
> center
> screw slot and two screws 180 degrees apart on the circle.  Those outer
> screws
> have lockwashers and each had a dab of glue.  From the manual it was clear
> that
> this is the holder of the grating.  I loosened the outer screws, and while
> the
> spectrometer's input fiber was pointed at the 405 nm laser spot, I slowly
> turned
> the center slot with a screwdriver.  It didn't take much turning (CCW)
> before I
> saw a strong response peak.  I moved it to sufficiently within the range
> and
> tightened the two outer screws.
>
> Now I turned to Appendix A in the HR2000 manual.  I had to locate a Hg
> lamp (I
> was able to find an antique scientific unit on feebay) as you will need
> several
> strong spectral lines within your range for the cal procedure.  I actually
> cheated slightly from the procedure, I made an educated guesstimate of the
> short
> wavelength being seen and loaded that into the unit with the USBprogrammer
> utility.  That made it a little easier for me to identify the Hg lines.
>
> Read the procedure all the way through and understand it before trying it.
>  Less
> hair pulled out that way.  I followed the instructions, did the linear
> regression as they specified in Excel (yes, an old version will work just
> fine),
> and loaded the correction factors into the unit's EEPROM (again, using
> USBprogrammer).
>
> I then plugged both my units in at the same time, and if you get
> SprectaSuite
> from Roland (he usually sends it on a CD) and you have multiple units, you
> will
> see both of their responses superimposed.  I pointed both fibers at the HG
> lamp
> (no, I didn't look into an unfiltered lamp!) and where the units ranges
> overlapped, the spectral lines coincided precisely.  I could have gotten a
> larger range, but for now I have two units with a combined range of about
> 370 to
> 670 nm.  I'm just not sure which end I want to expand another 100 nm.
>
> The procedure overall is not that difficult, and I got it right on the
> first
> try, but you MUST have a source of a multitude of spectral lines!  The
> good part
> is that you don't have to open the unit up, so no chance of getting any
> dust
> inside.
>
> One note:  theu nits have a mulitpin connector on one of the edges.  I
> found
> that ambient light was getting in and raising the overall "dark" floor.
> The
> cure was simply to place a piece of black vinyl electrician's tape over
> the
> connector, flush with the case.
>
> Any questions, feel free to contact me off-list.
>
> Peter
>
> P.S., John, please forward to the microscopes group.  I joined the
> Tekscopes
> group and ended up with a mountain of scopes, and the time-nuts group and
> now
> have a pile of time measurement and standards stuff, so no way I'm joining
> the
> microscopes group.  I have just one, and it's crappy but works, and I'll
> just
> stop right there while I can still afford rent.
>
>
>
> On 1/23/2012 10:32 AM, J. Forster wrote:
>> I've been bombarded with emails about retuning the spectrometers. I'll
>> get
>> the info and repost it in the near future, unless Peter would prefer to
>> put it up himself.
>>
>> Best,
>>
>> -John
>>
>> ==============
>>
>>
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