Updated 20 July 2023

Recent updates: Audio Recording, Unimat 3 Lathe - new 12 volt motor and PWM speed control, HP-12C Financial Calculator, Mercury Photoacoustic Effect, RladderP - Resistance ladder calculation, South Island trip - November to December 2021, Revised Visible Light Microscopy, InductanceP - Calculate inductance with a signal generator and an oscilloscope, Ion Pumped Mass Spectrometer

Photoacoustic mercury analyser working in igloo laboratory, Polar plateau, Antarctica
Photoacoustic mercury analyser working in igloo laboratory, Polar plateau, Antarctica


I retired from a science career in spectroscopy, microscopy, instrumentation and chemistry in 2010. I have a PhD from Victoria University of Wellington.

This web site is patterned on one I created when I was working at Victoria University. That site, featuring the JEOL 733 electron microprobe, is archived here. To maintain this site I use Smultron, which is a simple Mac editor. The current size of the whole website is about 140 MB.

The notes provided here are mainly for my reference. I find it easy to update HTML and the information looks nice and is easy to find. If others can find anything useful here then that is good. I do try to update pages to correct mistakes and to improve the content. This Oxide Conversion Table is popular, probably with geology students. I hope there is something here of interest. Obviously there are still errors present which I hope to find sometime.

Several projects are finished or some critical item has failed after a decade or so. I have arranged these projects at right under "Completed Projects" I may get around to fixing what is wrong if it is not too expensive.

Commercial Work

Occasionally, I did some commercial work using my experience in microscopy, electronics and mass spectrometry. Some time ago I researched improvements to the lost-wax gold casting process for a Chicago manufacturing Jeweller. This work resulted in a provisional US patent.

I developed a simple and precise dual 10MHz oscillator for use as a replacement in plastic film thickness measuring equipment. An oscillator was recently sent to Mitsubishi Polyester Film GmbH, in Germany, to allow a film thickness profiler to be repaired.

Recently one Dycor mass spectrometer was used for several weeks monitoring a pilot plant for evolved gases. This instrument was then donated to the Callaghan Institute, as accommodating two home-built, and working mass spectrometers, was a bit much.

Scientific Instrumentation

I was interested in developing, modifying and using scientific instrumentation and I used my electronic, mechanical and optical skills to achieve this. I also had some skills in product design. Most of the instrumentation, featured on this web site, was developed or modified since I retired more than a decade ago.

I have assisted research groups in Pakistan and the USA with JEOL 733 Electron Microprobe Repairs.


Portable Mass Spectrometer

In 1995 I built up a portable mass-spectrometer comprising a Dycor MA200m mass spectrometer matched with an oil free Pfeiffer Molecular-Drag vacuum pumping station. The mass range was from 1 to 200 daltons. A platinum furnace was available to heat solid samples for evolved gas analysis. A membrane inlet was used for routine gas sampling and it could also sample gases dissolved in liquids. This use of this Dycor mass-spectrometer solved several on-site industrial problems.

A variation of this design used an ion pump and a membrane inlet. This version operated independently from mains power at a number of sites. It could be run from four car batteries for up to 10 hours a day. Wet gases or gases dissolved in liquids could be directly measured with the membrane inlet. The instrument is supported with MASSPORT software.

In 2019 an Ion Pumped Mass Spectrometer was built from scrap parts. It is an old Dycor MA100m mass spectrometer with a used 8 l/s Varian ion pump. A novel membrane inlet, which can be closed when not in use, completes the design. The membrane inlet is designed to match the reduced pumping rate of the small ion pump, so it is smaller in diameter and thicker than typical. This instrument mainly helps with software support, while my other mass spectrometer is used by a client. It is also, occasionally, a practical and useful mass spectrometer.

ion pumped mass spectrometer
ion pumped mass spectrometer

Plasma Asher

My small and novel plasma ashing system can completely ash organic samples at room temperature. There is no significant heating of the sample and ashing occurs without any pyrolysis or charring. This means that volatile inorganic elements are not lost from the sample. The fragile inorganic structure of a biological sample can be revealed for microscopic examination.

Ultra clean surfaces can be prepared using this technique. Hydrophobic plastic surfaces usually become hydrophilic. This can improve the performance of adhesives.

A miniature fuel-cell based oxygen generator doubles the ashing rate for graphite to about 10mg per hour for a 0.5g sample. Cellulose ashes at a similar rate. Reversing the cell generates hydrogen, which can perform reduction reactions in the plasma. For example, the reduction of cellulose, forms an oil.

plasma asher
Plasma Asher

Visible Light Microscopy

Visible light microscopy features my various microscopes and cameras which have been developed and purchased for the photography of small objects. Samples can be imaged using incident, transmitted, polarised, circularly-polarised, or dark-field illumination. I own a Leitz research-class polarising microscope with a 3.2 MP Omax digital camera with variable LED illumination powered from any USB port.

The following topics may be of interest:

  • A section to help beginners to get started with microscopy.
  • Variable microscope illumination using white LEDs and any USB port as a 5 volt power source.
  • A discussion on digital camera requirements for the best image quality.
  • A section on polarised light microscopy.
  • Using circular polarisers with their included 1/4 wave plates.
  • Dark field and circular-oblique illumination.
  • Stereo microscopes with polarised light.
  • Sample tilting required for good photography through one stereo microscope eyetube.

White industrial hairnet, Kyowa stereo microscope, two circular polarisers, Omax 1.3 MP camera
White industrial hairnet, Kyowa stereo microscope, two circular polarisers, Omax 1.3 MP camera

Scientific Calculators

I own a compact DM15 scientific calculator and a standard size DM15L scientific calculator from SwissMicros and I have written a description of these calculators here. They are functionally equivalent to the hp-15c from Hewlett Packard, which is no longer made. I also use the hp-15c Simulator written by Torsten Manz for my program development. I have helped a little with the debugging of this program. My DM15 calculators can connect to this software for downloading programs and updating. I maintain a hp-15c Program Index which links to many fully documented programs.

SwissMicros DM15 scientific calculator
SwissMicros DM15 Scientific Calculator with my 1974 hp35

Photoacoustic Mercury Analyser

I developed a novel Photoacoustic Mercury Analyser when I worked at the DSIR. This was successfully used in the measurement of mercury in a range of samples, including air, water and snow. It was used for a few seasons in Antarctica. The instrument could measure less than 1 picogram of mercury in the sample cell. Pre-concentration, using a gold collector, allowed natural mercury levels in air to be determined.

Unimat 3 Lathe - Dremel Milling Attachment

I have added a Dremel Rotary Tool, with a micrometer controlled feed adjustment, to a Unimat 3 lathe. The setup allows the small scale accurate milling of alloys and plastics and is pictured at right. The Unimat 3 Lathe - Dremel Milling Attachment allows me to machine items which need to fit together and to accurately locate and drill holes for joining them.

Completed Projects

Portable X-ray Spectrometer

I have mounted an Amptek X123 X-ray spectrometer on an Equipoise-lamp arm along with a shielded 1 µC 241Am source from a domestic smoke alarm. The spectrometer can be used to safely establish the presence of elements from sodium to uranium without altering or touching the sample. This is is helpful when valuable artefacts need to be studied. Any object can be studied by placing it near the detector. Many objects can yield useful results in a few minutes. Non-metallic samples may take longer. The whole system packs into a briefcase.

X-ray Spectrometer
X-ray Spectrometer

This instrument can no longer be used as the detector has finally failed due to a window fault after more than 10 years of continuous use on many projects. Over time some clients purchased up-to-date portable x-ray analysers for their own use, once they saw what this simple instrument could do. I hope I can get the equipment working again, maybe with a mylar window in a light-proof housing or perhaps under vacuum for light element detection. A new PIN detector is the best option for future use. In addition a ROM upgrade is needed for use with modern Windows computers.

Mocon Thickness Profiler Repair

The repair of a Mocon profiler, which measures the thickness of multilayer plastic films, resulted in the development of a small, stable and precise replacement oscillator. The original oscillator was prone to failure and was very costly to replace. The new design has worked well long term so the project is now finished.

In 2020 I supplied an oscillator to a large company in Germany.

Camera Stabiliser

An inexpensive camera stabiliser was developed to help my non-stationary hands make some watchable short videos of some of our activities, along with some still photos. The stabiliser is designed for the Canon G15 camera and it is simple and effective. It has been built in two low cost versions with one version shown at right.

Gas Chromatograph with a Fuel Cell Generated Hydrogen Carrier

I modified a HP 5720A Gas-Chromatograph. by adding two PEM fuel-cells run as water electrolisers. Bottled carrier gases are not required. One cell supplies hydrogen as the column carrier while the other supplies make-up hydrogen for the flame ionisation detector. Either gas flow can be varied to suit the application by simply changing the cell current.

Miran Infrared Spectrometers

A Miran 1A infrared spectrometer can be used at any wavelength from 2.5 to 14.5 microns. A wide range of organic compounds in gases can be detected. The cell path can be varied from 0.75 to 20.5 metres. The official manual was missing so I wrote my own JEP Miran 1A manual. I also have a Miran 103 infrared spectrometer. This differs by having a cell with a fixed 13.5 metre path length. It uses a range of plug-in interference filters for wavelength setting. My filters allow the analysis of carbon monoxide, ethylene oxide, nitrous oxide and halothane. The operation is otherwise similar to the Miran 1A.

iPod Nano Watch

This milling setup was used to make a backing plate which turns an iPod Nano into a watch. This item is more useful than expected. I get the time, a stopwatch, a timer, music, podcasts, iTunes U, a photo album, a pedometer, an audio recorder and a radio all on my wrist. The illuminated display is a useful torch at night.

I store notes, like medical data, phone numbers, and bus times, as the lyrics of a few memorable songs. This is a simple cut and paste operation using "Get info" in iTunes. The battery lasts a reasonable time, depending on the task. Current smart-watches display phone messages and not much else. For this my cellphone is usually nearby, in my pocket. A Warning - the display is black and under glass so the iPod can get extremely hot if worn in direct sunlight. This will likely cause damage, in my case the on/off switch became faulty from adhesive movement inside.


Giant Expressway 2 Folding Bikes

Since January 2013 I have resumed cycling using my Giant Expressway 2 Folding Bike. I purchased this Bike as an easy re-introduction to cycling and to improve my strength, fitness and balance. At the time the only folding bike that I could find locally was the Giant Expressway 2, so that was my choice. I purchased a second bike so Désirée could ride with me. Look at Dizzy's folding bike blog for details of our rides.

At Seagull Hill near Wedderburn
At Seagull Hill near Wedderburn

Tarini Mountain Bike

I have completely upgraded my old Tarini mountain bike, including rebuilding the wheels with stainless steel spokes. The bike is fitted with new Maxxis DTH wide tyres which suit my tastes in riding. I first started riding again with this bike but I needed to ride on flat areas, initially. The folding bikes were more convenient to transport in our small car. Since then I have regained some fitness and I now ride this bike around the local hills.

Jamis Allegro Sport Fitness Bike

I also have a Jamis Allegro Sport fitness bike to use mainly for solo road cycling. I have reviewed this bike here. This bike now has new and wider Vittoria Randonneur Tech 700x40c tyres fitted for road and trail riding.

SmartMotion e20 Folding Electric Bikes

More recently we purchased two New Zealand designed SmartMotion E20 folding Electric Bikes to allow us to undertake a wider range of rides in our hilly home town of Wellington, New Zealand. The electric bikes have the added benefit of making our rides more sociable as we now ride at similar speeds. Both bikes have performed well for more than 6 years use and 10,000 km covering much of New Zealand. We still ride the Giant Expressways on easier routes.

Wellington from Mount Victoria
Wellington from Mount Victoria


Email: replace at with @


Audio Recording

HP-12C Financial Calculator

Curve Fitting

Dycor Mass Spectrometer

hp15c Program Index

Mercury Photoacoustic Effect

Plasma Asher

SwissMicros DM15 Scientific Calculator

Unimat 3 Lathe - new 12 volt motor and PWM speed control

Visible Light Microscopy


A Black Flame

A Ceramics and Photographic Exhibition

Favourite Photos

Hesperus the Pack-Cow

Kuiper Airborne Observatory

Recent Photos




Dizzy's Folding Bike Blog

Bike Reviews

Bickerton Portable Folding Bike

Giant Expressway 2 Folding Bike

Jamis Allegro Sport Fitness Bike

SmartMotion e20 Folding Electric Bike

SmartMotion eMetro Electric Bike

SmartMotion Vista Folding Electric Bike

Electron Microprobe

JEOL 733 Electron Microprobe

JEOL 733 Electron Microprobe Repair

Oxide Conversion Table

Completed projects

Amptek X-ray Spectrometer

Camera Stabilizer

HP Gas Chromatograph

Mocon Profiler Repair


Related Links

Arts & Letters Daily

Bike Snob NYC

EEVblog Electronics Engineering Video Blog

Lovely Bicycle

Pedelecs Electric Bike Community


The Online Photographer

Universe Today


The name of this site adds the initials of my name, John E Patterson, to "spectro", from spectroscopy. The logo above is a stylised "JEP" with overlapping letters. The colours represent spectroscopy.

My CV is here.

John Patterson

Hover the mouse over a photo for a title. Clicking on a photo takes you to a related link or gives you a larger version.

Amptek X123 X-ray spectrometer Amptek X123 X-ray spectrometer

Leitz Microscope with Omax 1.3 MP camera Leitz Microscope with Omax 1.3 MP camera

Picture of Dycor Mass Spectrometer Dycor Mass Spectrometer

Camera Stabilizer Camera Stabilizer

Sampling air for mercury at Lake Vanda Sampling air for mercury at Lake Vanda

Black flame - Sodium lamp behind Black flame - Sodium lamp behind

Halley's Comet Halley's Comet

Unimat 3 Lathe - Dremel milling attachment Unimat 3 Lathe - Dremel milling attachment

Ipod Nano watch Ipod Nano watch

Pencarrow Head, Wellington Pencarrow Head, Wellington.

Tarini Mountain Bike Tarini Mountain Bike - Wellington

Tinakori Hill - Wellington Tinakori Hill - Wellington