When it arrived I looked inside the large box and found it was indeed a standard 486DX-2 66MHz PC, complete with two HDDs and a Data I/O DataAcq DT21-EZ analogue/digital I/O card [D24].
All the cables were numbered, making it very easy to assemble. A flat cable ran from the I/O card into a large black box on the rear of the Sp-275 spectrometer, and another from the PC serial port to a small box with a keyboard and LCD, also connected to the Sp-275, and mandatory for its operation.
I added an XT PC keyboard, serial mouse and VGA monitor and although it came to life, it didn't boot.
Examining the motherboard I found a Dallas DS1687-5+ realtime clock module soldered in, which I knew contained the BIOS battery.
Undeterred I stripped the PC and unsoldered the chip, replacing it with an IC socket and fitted an equivalent Twin Head TH6887A I'd bought on eBay usa, which also didn't work.
This website goes into more detail about these modules: http://greyghost.mooo.com/th6887a
There was an option to add an external battery, but I next found a DS1232 which was much easier, and worked.
2. Plasma Chemistry Monitor
Approaching Xmas 2009, a vaguely familiar piece of equipment appeared on eBay - an SC Technology
PCM-401 Plasma Chemistry Monitor.
I assumed it was an earlier model of the $7k PCM-403 I'd seen months earlier, except this one wasn't working and it was still very expensive at $1250.
This time there was no PC visible, but the 3.5" floppy drive on the front of the large white rack-mounted chassis suggested it could be a PC, and the fact it didn't work might be down to its BIOS battery being empty. The seller had assumed the word Monitor meant a PC monitor, so clearly had no idea what it was.
The spectrometer was an older, obsolete Acton Research SpectraPro Sp-275 (manual here:[I16]), but externally it looked in good shape and although there was no software included, all cables appeared present and it also had a mercury vapour (Hg) calibration lamp, and an extra couple of boxes I hadn't seen before.
I should point out that although I had seen proof of what the PCM-403 did, I had no idea what its intended use was, how to operate it, or even if it would work with a laser, and no proof this one would do the same thing.
I took a very large gamble and bought the faulty
PCM-401 without the rack, which was too small for what I had in mind and saved shipping expense.
The PC booted, but hung. I rebooted to the BIOS and set it to auto detect the HDDs, which it did, and then amazingly it booted to Windows 95 R1. Even more amazing, the HDD still had the precious Plasma Chemistry Montor software installed, and it worked!
I played with the software for a while, adjusting settings and selecting different gratings in sequence, observing each provided a finer level of resolution over the entire available range of 200nm to 1000nm.
For instance, I selected Grating 1 (lowest resolution), screwed the SMA FO cable into the Hg calibration lamp and invoked a scan which brought up a broad range of peaks as expected. But there was also an I/T plot to the right, whose purpose was not immediately apparent.
Sp-275 gratings:
G1 = 150g/mm Blaze 500nm, Range 600nm (e.g. 200nm - 800nm)
G2 = 300g/mm Blaze 300nm, Range 300nm (e.g. 350nm - 650nm)
G3 = 1800g/mm holographic, Range 40nm (e.g. 480nm - 520nm)
I found a manual online for the Sp-275 monochromator which said a 1200G/mm grating resolution is 0.1nm (with 10µm slit; accuracy ±0.2nm, reproduceability ±0.05nm), so I guess at 1800g/mm it is 0.07nm.
I was lucky to find the manual for the monochromator, but not so for the PCM-401. Like most eBay purchases, it arrived with no documentation and there was none I could find on the web. The manufacturer S.C. Technology no longer exists, but a company called Telemark appeared to have bought the rights and offered a newer PCM-420 system based on a laptop, with a very similar looking screenshot, but this too is no longer available (2009 brochure here: [O10]).
Fortuitously, the PCM401.EXE software has embedded help which has proved invaluable but it was a long while before I found a way of extracting the text of its standard MS HLP file PCM401.HLP to enable me to examine all of its many pages as a single document. All the free online MS hlp file converters I tried crashed, but free DOS utility 'HELPDECO' by Manfred Winterhoff [S4] worked. It can be easily run in the Windows command window. To the right is the process I followed to convert the PCM401.HLP file:
It split the HLP file's graphics into lots of WMF files and collated all of the separate pages of text into a single RTF file, PCM401.RTF. I have yet to find a way to reconstruct them all into one readable file without involving a lot of labour (free HLP file creators exist), but it is a simple matter to read the RTF file and then examine the original HLP file for the topic of interest.
Below I've converted online [C23] the RTF into a PDF file:
I asked Telemark if they had installation floppies for the PCM-401, and if they could provide any documentation, but they said neither existed, so it was up to me to find out how the system worked, and to find a way to preserve it should its HDD ever fail.
One of the first things I noticed in the online help was it has a calibration facility that requires the Hg lamp supplied with it, together with a tungsten calibration lamp. By fortune I had bought one of these for use with the Stellarnet EPP2000.
I ran the calibration routine with some apprehension, aware that upon calibration failure, some instruments can lock themselves into a functionless state, demanding a service. It was some relief when it reported everying was fully functional, with an impressive maximum wavelength error of 0.02nm.
Incredibly, the appended calibration report revealed the previous owner, HDD manufacturer Seagate's NPD (New Product Development) R&D lab, appeared not to have used a tungsten calibration lamp, and the machine was now set up better than they had it!
CALIBRATION REPORT: Spectrometer
Grating number 3
DATE: 5/12/10 TIME: 12:24:53 AM
Wavelength test passed
Maximum error: -0.02 nm at 253.65 nm
Average error: 0.01 nm
Bandwidth test passed
Bandwidth Max. FWHM : 0.20 nm at 404.66 nm
Bandwidth Min. FWHM : 0.10 nm at 871.67 nm
Average bandwidth: 0.17 nm
CALIBRATION DETAILS:
Actual Measured Diff. Corrected Diff. FWHM
-----------------------------------------------------
253.65 253.33 -0.32 253.65 0.00 0.17
296.73 296.42 -0.30 296.73 0.00 0.17
313.15 312.85 -0.31 313.15 0.00 0.19
365.02 364.75 -0.27 365.04 0.02 0.18
404.66 404.38 -0.28 404.65 - 0.01 0.20
435.83 435.55 -0.29 435.81 - 0.02 0.18
546.07 545.86 -0.21 546.09 0.01 0.19
809.31 809.19 -0.12 809.31 - 0.01 0.11
871.67 871.57 -0.09 871.67 0.00 0.10
Over the following months I experimented with the PCM-401, reading the embedded help file, trying to learn what the instrument did and how it worked. Eventually I also understood the description on Telemark's website. The PCM-401 is a plasma etch endpoint detection and feedback control system.
In layman's terms, it was intended to control a semiconductor manufacturing foundry.
Background: semiconductors and ICs in particular, are made in furnaces which etch and deposit compounds in gradual layers. The PCM-401 spectrometer has an armoured FO cable which would have been placed near the furnace, where wavelengths in the furnace plasma revealed the concentration of elements in the process. This process takes a certain amount of time to complete each stage. For instance, a gas like Nitrogen might be used to stop a chemical reaction and this could be evidenced by the gradual reduction of some elements in the plasma. The PCM-401 would be programmed to detect a certain level and turn off the Nitrogen, vary the furnace temperature, perhaps open a valve to admit the next chemical, etc., whatever was needed to control the process. The point at which the level is detected is called the endpoint. In addition to input signals that can be electrical or optical, it has output signals to control the process and two graphs: one a conventional spectrograph from 200nm - 1000nm, and an I/T graph - intensity versus time, thus it is able to determine when a chemical reaction has peaked, by detecting the intensity of reactors. The chemical composition is referred to as a species.
The next thing was to see if it could detect elements from its library. I selected Hg from its element table and with the FO cable again screwed into the Hg lamp, took a scan and clicked IDENTIFY SPECIES. It didn't. After a while I realised I had to scan using high resolution Grating 3 for it to accurately differentiate peaks. The library identified peaks it expected for each element, so it was just a matter of zooming in on potential candidates. NOTE: IT IS POSSIBLE THIS WAS DUE TO ACCURACY BEING SET TO 1.2NM ON THE LOW RES GRATINGS AS WELL (SEE PCM HLP PAGE 4).
Stellarnet utilises the close proximity of Hg peaks 577.6nm and 579.2nm as a measure of spectrometer prowess. Below left my original EPP2000 SR shows spiky twin peaks. Later when I tried the 16-bit Black comet SR it was clearly a more accurate looking plot but I was puzzled why it also appeared inferior as the 579.2 peak is not as high as the 577.6 peak and has a dip in the middle of it. The PCM-401 is a order of magnitude more accurate and dips in its own peaks hint they may themselves be doublets. Initially I was annoyed the 16-bit BC seemed to be less accurate than the old 12-bit EPP but then I remembered the dips in the PCM-401 plot. As with the EPP the BC only seems to have about 3 sample points for this peak. I know it's unlikely (otherwise the PCM would surely show it?) but I'd like to think the extra sensitivity of the 16 bits picked up one of those dips...
Below left: Below right:
577.6nm & 579.2nm peaks on The same peaks on the PCM-401, the dips at the top of each peak
12-bit Stellarnet EPP2000SR: hint they may themselves each be a doublet:
Above left:
16-bit Black Comet SR hints at a peak doublet at 579.2nm
The PCM401 plasma chemistry monitor 80 species library can
detect 9 elements and 41 compounds, as below (RE=reactive).
I added some common sources I might use to validate them: Below right: PM401 species library
# Elements Potential test source # Compounds
1 Ag Silver coil 1 AlCl
2 Al Aluminum metal 2 AlH
3 Ar Argon Ar laser / Ar gas / USSR IN-9 3 AlO
4 As Arsenic - 4 AsF
5 Au Gold plating 5 BBr
6 B Boron magnet 6 BCl
7 Be Beryllium spring 7 Br2
8 Bi Bismuth solder / souvenir / TEC 8 Br2+
9 Br Bromine - 9 BrCl
10 C Carbon rod / zinc battery 10 BrF
11 Cl Chlorine - 11 BrO
12 Cr Chromium plating 12 CCl
13 Cu Copper pipe 13 CF
14 F Fluorine - 14 CF2
15 Fe Iron filings 15 CH
16 Ga Gallium Oriel arc lamp repair syringe 16 CN
17 Ge Germanium - 17 CO
18 H Hydrogen - 18 CO+
19 He Helium HeNe laser 19 CO2+
20 Hg Mercury Hg lamp 20 GaCl
21 In Indium heatsink 21 GaF
22 K Potassium - 22 HBr
23 Mn Manganese - 23 InO
24 Mo Molybdenum grease 24 N+
25 Na Sodium RE salt 25 N2
26 Ni Nickel plating (component leads) 26 N2+
27 O Oxygen - 27 NH
28 P Phosphorus RE match 28 NH+
29 Pb Lead metal 29 NO
30 Pt Platinum spark plug 30 O2+
31 S Sulphur Lanzarote volcano souvenir 31 OH
32 Se Selenium solar cell 32 SiBr
33 Si Silicon chip 33 SiCl
34 Sn Tin metal 34 SiF
35 Ta Tantalum capacitor 35 SiF2
36 Ti Titanium - 36 SiH
37 W Tungsten lamp 37 SiN
38 Zn Zinc plating (nails etc) 38 SiO
39 Zr Zirconium - 39 SnO
40 TiO
41 ZnO
It wasn't until 2015 that I finally solved a problem that had bugged me from the day I bought it - finding a way to back up the software on the PCM-401 HDD, a tiny 210MB Conner CFS210A), as there was a very real possibility it could fail at any moment and I would lose the software before I could use it. I saved its help file and kept use to a minimum. With no installation floppies (I'm still looking), I tried copying all files to another PC and running the executable (which sometimes works), but the DLLs (Dynamic Link Library files) that had been installed and registered with it were missing.
I was hesistant to install any backup software on the original hard drive for fear it might corrupt the existing installation so instead I gingerly removed the HDD, changed its jumpers from Master to Slave and placed it in an old Windows 2000 PC together with a used CFS210A from eBay.
I ran Partition Magic and copied the PCM-401 HDD to the new HDD, but when I put the new drive back in the PCM-401 it failed to boot, the BIOS reporting an I/O failure.
I considered sending the drive away to be professionally copied, but this would be very expensive and I discovered a few horror stories about companies who did this.
Finally in 2015 it occurred to me that old IDE duplicators were probably quite cheap by now and I looked for one on eBay.
Sure enough, I found an ICS2000 Masstor replicator for $120.
The manufacturer kindly emailed the latest firmware image to me (it runs from a 3.5" floppy):
I breathed a huge sigh of relief when I was finally able to copy the drive onto 2 new CFS210A drives I had eventually found.
Having suffered an I/O failure before, this time I made sure I got new ones, albeit ancient.
This time I used the exact same HDD to minimise issues; later I ported it to larger modern HDDs and eventually, SSDs.
RUNNING THE SOFTWARE ON ANOTHER PC
Before I replicated the original HDD I thought I might be able to simply install Win 95 on a PC and copy over the installed PCM-401 software. Its OS identified as Windows 95 Release 1, so I bought a fresh copy on eBay and installed it on a spare hard drive on my old but still functional ISA-bus Intel P233MMX PC. However the PCM-401 software didn't run, saying a DLL was missing. I found a copy of the DLL on the internet but then it complained another DLL wasn't present that I could not find, and I had to abandon this idea.
Having successfully copied the HDD onto a couple of new CFS420 HDDs, I installed one into the Intel P233MMX PC which has a Matrox Millenium GPU. At first it didn't boot, but when I disconnected the monitor then reconnected it when the HDD LED went off, I found it had booted in safe mode. I was then able to load the Matrox Millenium GPU drivers and get it to boot properly. I then replicated the updated HDD to one of the CFS420s as a backup.
I found there is no provision for SCSI in the Win 95 R1 Control Panel on the PCM401 HDD, so it was not possible to add a SCSI DVD-RAM, which had been my means of storage up until CF memory cards became mainstream (USB not yet invented at the time of Win 95). SCSI capability is present on my own Win 95 R1 install from scratch, so SC Tech must have installed a cut-down OS version of Win 95 R1. However I was able to add a 256MB CF card using an eBay China CF to 40-pin IDE adaptor [D25] (photo below left), although this is of course not hot-swappable like USB, so can only be changed when power is off. I was also able to add a CD-ROM, as per the original installation and of course a 3.5" floppy.
Having got the PC to run, I invoked PCM401.EXE but it failed to open because the spectrometer wasn't present (photo below right):
PCM401 / SPECTROMETER INITIALISATION SEQUENCE
In 2011 I had found a spare DataAcq DT21-EZ I/O card priced at $1200 for which the seller amazingly accepted my offer of $200, and I now installed this in a spare ISA slot in the Win 95 R1 P233MMX PC, and ran a 50-way IDC cable out to a socket for signal detection - see [Prototype Integration].
Meanwhile I hooked up the serial port on my normal PC (which at the time was running Win 2k) to the serial port on the Win 95 PC. Initially I confirmed the presence of RS-232 signals on my Rigol oscilloscope [I13, I14]:
Once I confirmed the signal format I installed a demo version of ComPortToolKit V3.8 under Win 2k to observe the serial comms from PCM401.EXE in an effort to see what it expected from the spectrometer to get it to work. The manual for the SpectraPro 275 explains the protocol and settings:
9600 baud, 1 stop bit, no parity
Set delay before messages to 1 second (it's in ms so enter 1000)
Set rx and tx boxes to 12 chars per line.
I then ran PCM401.EXE and was able to capture its communication to the spectrometer.
'HELLO', not documented in the manual, initialises the spectrometer. Once I could do that, I could replicate the entire exchange of messages from the other PC using a ComPortToolKit macro file so PCM401.EXE thought it was talking to the spectrometer. It is necessary to add a delay of 1 second between messages (a feature of ComPortToolkit) or else PCM401.EXE will think the spectrometer hasn't initialised.
The following exchange is needed for the correct load sequence:
Note - every byte must be perfect or it will hang (but may eventually load).
<SP> = space, <.> = dot
1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends <SP><CR>
<SP><CR>
20 0D
Spectro sends ' OK'
<SP><SP><SP> O K <CR><LF>
20 20 20 6F 6B 0D 0A
2 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends ' HELLO<CR>'
<SP> H E L L O <CR>
20 48 45 4C 4C 4F 0D
Spectro sends ' Acton Research Corp. SpectraPro Monochromator V3.0 OK'
<SP> H E L L O <SP> A c t o n <SP> R e s
20 48 45 4C 4C 4F 20 41 63 74 6F 6E 20 52 65 73
e a r c h <SP> C o r p <.><SP><SP> S p e
65 61 72 63 68 20 43 6F 72 70 2E 20 20 53 70 65
c t r a P r o <SP> M o n o c h r o
63 74 72 61 50 72 6F 20 4D 6F 6E 6F 63 68 72 6F
m a t o r <SP><SP> V 3 <.> 0 <SP> O K <CR><LF>
6D 61 74 6F 72 20 20 56 33 2E 30 20 6F 6B 0D 0A
3 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends ' ?GRATING<CR>'
<SP> ? G R A T I N G <CR>
20 3F 47 52 41 54 49 4E 47 0D
Spectro sends ' ?GRATING 1 OK<CR><LF>'
<SP>? G R A T I N G <SP> 1 <SP><SP><SP> O K <CR><LF>
20 3F 47 52 41 54 49 4E 47 20 31 20 20 20 6F 6B 0D 0A
4 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends ' ?NM<CR>'
<SP>? N M <CR>
20 3F 4E 4D 0D
Spectro sends ' ?NM 0.0 OK<CR><LF>
<SP>? N M <SP> 0 <.> 0 <SP><SP><SP> O K <CR><LF>
20 3F 4E 4D 20 30 2E 30 20 20 20 6F 6B 0D 0A
5 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends ' 692.0 GOTO<CR>' <----------692nm is from last use of PCM401
6 9 2 <.> 0 <SP> G O T O <CR>
36 39 32 2E 30 20 47 4F 54 4F 0D
Spectro sends ' 692.0 GOTO OK<CR><LF>'
6 9 2 <.> 0 <SP> G O T O <SP><SP> O K <CR><LF>
36 39 32 2E 30 20 47 4F 54 4F 20 20 6F 6B 0D 0A
6 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends ' ?GRATING<CR>'
<SP> ? G R A T I N G <CR>
20 3F 47 52 41 54 49 4E 47 0D
Spectro sends ' ?GRATING 1 OK<CR><LF>'
<SP>? G R A T I N G <SP> 1 <SP><SP><SP> O K <CR><LF>
20 3F 47 52 41 54 49 4E 47 20 31 20 20 20 6F 6B 0D 0A
7 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PCM401.EXE sends ' ?NM<CR>'
<SP>? N M <CR>
20 3F 4E 4D 0D
Spectro sends ' ?NM 692.0 OK<CR><LF>'
<SP>? N M <SP> 6 9 2 <.> 0 <SP><SP> O K <CR><LF>
20 3F 4E 4D 20 36 39 32 2E 30 20 20 6F 6B 0D 0A
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
If the grating info isn't returned it still boots up, just sets its own defaults (probably the last used). The full ComPortToolKit boot-up sequence is shown below:
I saved the macro sequence as a text file that I could load into ComPortToolKit.
Bizarrely, Wix won't import txt files so its content is here instead:
20,20,20,6F,6B,0D,0A;
20,48,45,4C,4C,4F,20,41,63,74,6F,6E,20,52,65,73,65,61,72,63,68,20,43,6F,72,70,2E,20,20,53,70,65,63,74,72,61,50,72,6F,20,4D,6F,6E,6F,63,68,72,6F,6D,61,74,6F,72,20,20,56,33,2E,30,20,6F,6B,0D,0A;
20,3F,47,52,41,54,49,4E,47,20,31,20,20,20,6F,6B,0D,0A;
20,3F,4E,4D,20,30,2E,30,20,20,20,6F,6B,0D,0A;
36,39,32,2E,30,20,47,4F,54,4F,20,20,6F,6B,0D,0A;
20,3F,47,52,41,54,49,4E,47,20,31,20,20,20,6F,6B,0D,0A;
20,3F,4E,4D,20,36,39,32,2E,30,20,20,6F,6B,0D,0A
Click on >>> symbol at top to right of minus sign to select send messages window. The sequence is then:
1. Connect Win 2k com port 1 to P233MMX com port 2 (com1 = mouse)
2. Connect it using a crossover 9D to 9D from the Win2k to a 1:1 9D/9D connector to the P233MMX.
3. Double click on PCM401.EXE on the P233MMX
4. As soon as you see 20 0D is received in ComPortToolKit rx box, click send file.
The PCM401.EXE should say Data acquisition card initialised then Spectrometer initialised, then should boot up with the (Aquisition tab) central wavelength set to 692.0nm:
The PDA signals etc., can now be examined without having the original PC or spectrometer hooked up, extending their lives. Again, refer to [Prototype Integration].
SEPTEMBER 2018 - WHAT I'VE LEARNED ABOUT S.C. TECHNOLOGY'S PCM SERIES
PCM-400 head (DOM 03/08/1988)
Not long after I bought the PCM-401 I saw a small SC Technology Plasma Chemistry Monitor PCM-400 on eBay that I naturally assumed was the predecessor to my PCM-401. It had a dual armoured fibre optic (FO) cable and a mysterious mechanical switch on the side with 4 positions labelled 200 250 300 350, and the familiar 50-way IDC connector socket on the rear. The first one I saw was $500 but several years later one appeared for $25. Its armoured fibre optic was damaged, but I was only interested in looking inside in the hope of finding a detector with a gated intensifier.
It appeared to contain a spectrometer, and the 4-way switch (bottom left) was a micrometer, very likely an entry slit width selector. The second armoured FO cable was from an internal Hg calibrator lamp
(the long silver pencil object at the top of the centre photo below - the normal fibre is below it):
The inside (above centre) looked very similar to the diagram of the detector (above right), containing a (Fastie-)Ebert spectrometer [O46], that I'd found in a 1991 paper partly authored by Richard Savage, (who I discovered was strongly associated with the design of the SC Technology PCM series, having patents issued in his name): [O42], Application of Optical Emission Diagnostics and Control Related to Semiconductor Processing'.
The initial portion of the abstract says: 'This paper will discuss and show applications of optical emission spectroscopy techniques and methods to monitor plasma emissions during semiconductor processing.' The paper then goes on to describe the system: 'Figure 1 shows the basic spectrometer system: Plasma emission is collected through fiber-optics 1 and sent into a 160mm Ebert spectrometer 2 where light is dispersed onto 512 photodiode array 4. Optional image intensifier 3 can be used to gain more sensitivity for low light applications. The data is sent to a PC based acquisition system which manipulates the data into useable form.' Essentially, it is a basic description of SC Technology's PCM.
Inside I found a label identifying it as a PSA-400 dated August 04, 1988. It had internal BNC connectors labelled GATE and TRIGGER but appeared to lack an image intensifier.
Better, it had a pcb with a hole in it through which I could read off the part number on the back of a linear PDA chip facing the spectrometer: Hamamatsu S2301-512Q (even if I saw the PDA side of the chip I would not be able to identify it because it is likely attached to the intensifier using a fibre optic conduit).
It is just possible SC Tech put a hole in the PCM-401 detector pcb too, so I do indeed need to go in deeper.
I could find no datasheet for the S2301; the nearest was a 1987 Hamamatsu S2300F (S2301) 256, 512, 1024 linear PCD (PDA) embedded in a paper, from which I created pdf [D19]. It says: 'the S2300 sensitive area is twice as large as the S2301 series...the S2301 PDAs are 50µm aperture long x 2.5mm wide'. This is a typo as it's 50µm spacing with 36µm aperture long x 2.5mm wide, confirmed on Page 2 of paper
[O45]: '...linear sensor with 256 pixels each size of 36μm x 2.5mm (Hamamatsu PCD S2301-256 Q)'.
If SC was using 2.5mm Hamamatsu PDAs in 1988, there is every likelihood they were also used in 1995 for my PCM-401 (DOM 08/03/95) and the PCM-403.
SCT-100 PROCESS SENTRY (1994)
The SC Technology paper [O42] qualifies its description with a number of plots towards the bottom, most of these being conventional spectrographs but two look like intensity/time (I/T) plots, and these are labelled 'Process Sentry'. All of the spectrographs and plots look very similar in format to the curves produced on the PCM-401, but sufficiently different for me to assume they were produced by the
SC Technology SCT-100 Process Sentry system that may be the PC controller for the PCM-400 detector head, since [O42] directly references both. The SCT-100 system has also been on eBay, but I have never seen one with a detector. Interestingly, I found an Interfacer II on eBay with a label on it saying it was for the Process Sentry. The only difference between it and the one that came with my PCM-401 is it has a PCM-401 label. To all intents, the PCs for the SCT-100 and PCM-401 look virtually identical:
Above - SC Technology SCT-100 Process Sentry SCT Data Station
Below - SC Technology SCT-401 Plasma Chemistry Monitor
PCM-401 (1995)
1997 paper on the web, [O50], Excited State Density Distributions of H, C, C2, and CH by Spatially Resolved Optical Emission in a Diamond Depositing DC-Arcjet Reactor, Page 2, lists some of the equipment used to verify atomic signatures in (slow) gas plumes: 'A SC Technology Plasma Chemistry Monitor 401, consisting of a spectrograph with a gated intensified photodiode array of 512 elements...'
From my website / the Sp-275 manual:
Grating 1 = 150 grooves/mm Blaze 500nm, Range 600nm (e.g. 200nm - 800nm)
Grating 2 = 300 grooves/mm Blaze 300nm, Range 300nm (e.g. 350nm - 650nm)
Grating 3 = 1800 grooves/mm holographic, Range 40nm (e.g. 480nm - 520nm)
The manual says 1200G/mm grating resolution is 0.1nm
(with 10µm slit; accuracy ±0.2nm, reproduceability ±0.05nm), so I guess at 1800g/mm it is 0.07nm (0.07nm x 512 = 35.84nm).
(from my reverse engineering)
Triple grating spectrograph
Spectral resolution: 0.07nm at best
Maximum wavelength error: (from my cal: -0.02nm)
Detector: PDA 512 pixels
High sensitivity range: 200-1000nm
Data acquisition: 12 bit, maximum rate: 6Hz (150ms)
PCM-403 (1997)
Page 173 of [L11], Plasma Processing IX, Proceedings Volume 98-4 of the Electrochemical Society, says: 'A Plasma Chemistry Monitor PCM-403...combines a triple grating spectrometer with an intensified photo diode array (1000 diodes) detector. The scan wavelength range/resolutions are:
Grating 1 has range 600nm/1.5nm resolution
Grating 2 257nm/1.0nm
Grating 3 50nm/0.2nm
Time to capture a single spectrum is 0.26sec.' 260ms = 3.85Hz.
The original 7k PCM-403 auction said:
Triple-grating Czerny-Turner spectrograph with micrometer driven slit (i.e. effectively 20 microns or greater - variable)
Grating 1 = 150 grooves/mm (i.e. 0.55nm/pixel) giving an effective spectral range of 533nm
Grating 2 = 300 grooves/mm (i.e. 0.28nm/pixel) giving an effective spectral range of 279nm
Grating 3 = 1800 grooves/mm (i.e.~0.10nm/pixel) giving an approximate spectral range of 36nm
Quantum efficiency of PDA is 75% @600nm with sensitivity (photons/count) 2200 @ 600nm
SC Technology 1024 element Photodiode Array (photosensitive area 25 microns x 2.5mm)
matched with intensifier (wavelength range 200-900nm).
[Reticon RL1024 datasheet says PD = 25µm spacing & PD size is 26µm aperture long x 15µm wide]
[Hamamatsu S3904 datasheet says PD = 25µm spacing & PD size is 20µm aperture long x 2.5mm wide]
It might be a Hamamatsu S3904-1024Q? (the PCM401 might be an S3901-512Q?).
Also of note, the original $7k PCM403 has a BNC on its PDA that isn't on any other PCM-403 I've seen, and the PDA connector fascia plate on both PCM-403s below is rotated 180 degrees vs the PCM-401. It is possible the BNC is a gate and as they are both rotated, my PCM-403 may have it inside too. OTOH The SC Tech PSA-400 head has a BNC inside its box marked TRIGGER and another marked VIDEO. Maybe the original PCM-403 unmarked BNC is one of these?
PCM-401 PDA: Original $7k PCM-403 PDA: Spare PCM-403 PDA:
Another thing on eBay was just the PDA itself from a PCM-403 (see top right & below). The seller described it as a Plasma Chemistry Monitor but clearly had no idea it was just the PDA. Although tempting as a spare there was no indication it worked, and having the intensifier exposed to all manner of dust and light probably did it no good. It was interesting however to see the intensifier in the assembly, below centre. Below right, a typical intensifier setup for a CCD; it would be similar for a PDA:
PCM-403 FINALLY AQUIRED
In 2018 I found another working PCM-403 on eBay Singapore at $7k, sadly without installation floppies. The lowest offer the seller would take was $3k5 including shipping, which I reluctantly paid, selling my Canon EF 500mm f/4L IS II USM lens to finance it as it had not been used in many years, its insurance premium now a waste of money. This is the lens I handheld with a 2x teleconverter to capture flying foxes above the rainforest canopy in Madagascar, see [Photography: Birds Bats].
The seller followed my strict instructions to carefully pack the PCM using solid foam and bubble wrap between all assemblies. Unfortunately he put the spectrometer at the bottom of a single huge box with very little padding below it and when it arrived the intensifier block was rotated at a crazy angle. I was able to free it and thankfully there was no sign of internal damage but when I tried to fire up the PC it hung, citing a BIOS fault. I stripped out the HDD and took a copy, but it was too late, the disc was damaged, and the more copies I tried to take the worse it got, implying disc head demise. I contacted the seller who offered me a 50% refund.
By pure chance, the HDD in my original PCM-401 had come with installed PCM-403 software which ran but returned bad values from its SpectraPro Sp-275 spectrometer. I assume they had upgraded the spectrometer at some point and initially used the 401 PC to drive it. I cloned the PCM-401 HDD onto a Sandisk SSD and installed this in my old ISA-bus Intel P233MMX PC and booted it. After a lot of fiddling I managed to get the PCM-403 software to run and produce what looked like a valid trace from the PCM-403's SpectraPro Sp-300i spectrometer.
I could have pressed for a complete refund but I felt sorry for the seller as he had tried his best to pack it well and the fault was with the couriers, not him. The PCM-403 PC was a goner, but I had managed to get it to work and I accepted his offer.
(My PCM-403 intensifier block doesn't have the mystery BNC either, so I am none the wiser.)
PCM-420 (2009)
Telemark's 2009 brochure says the S.C. Technology PCM-420 has:
Double grating spectrograph
Spectral resolution: hi-res 0.35nm, low-res 4nm
Maximum wavelength error: hi-res 0.25nm, low-res 0.4nm
Detector: TE-Cooled back illuminated CCD array, 1024x256 pixels
Detector Quantum efficiency: 90% @ 600 nm
High sensitivity range: 200-1000nm
Data acquisition: 16 bit, maximum rate: 40Hz
Linearity: 99.8%
Signal-to-noise ratio: 3000:1
http://www.cryosystems.ru/wp-content/uploads/2010/10/Plasma-8-25-09.pdf
However Page 3 of [O6], Supersonic Metal Plasma Impact on a Surface: An Optical Investigation of the Pre-Surface Region, says: '...moderately-high-resolving spectrometer (PCM-420 by Telemark,
spectral range 350nm to 1050nm, ~0.05nm)'.
At first glance it looks like the PCM-420 has a less accurate spectrometer than earlier PCMs, with two gratings for increased speed at the cost of poorer resolution offset by a TEC-cooled 2D CCD in place of an intensified PDA (earlier PDAs were more sensitive to UV than CCDs). However the 2D CCD is suggestive of a superior echelle spectrometer. It does have the fastest acquisition time (40Hz = 25ms), but still far too slow for LIBS without gating.
OTHER PCM SYSTEMS
At least since April 2015, Telemark has offered their own CCD based NVision Optical Monitor in place of the PCM-42x series they acquired from SC Technology:
https://telemark.com/optical-instrumentation/multi-point-optical-monitor/#specs
It appears Hamamatsu has had a USB 2.0 based PCM since 2020. The features page indicates coverage from 200nm to 950nm covering 15k spectra up to 20ms (hardware), 50ms (software):
https://www.hamamatsu.com/eu/en/product/semiconductor-manufacturing-support-systems/plasma-process-monitor.html