History of PMS Instrument - Joe Zaerr

Author: Co-Founder of PMS Instrument Company, Joe Zaerr

I arrived in Corvallis in September, 1965, to take a position as Assistant Professor of Forest Tree Physiology at OSU. I had just completed a one-year Post Doctoral Fellowship at the USDA Research Station in Beltsville, MD, and was eager to get started on a regular job. As I was casting about to discover some promising areas of research, Dick Waring (whom I knew as a fellow graduate student at UC Berkeley a few years earlier) invited my to go on a field trip with his MS student to the Siskiyou mountains in Southern Oregon to collect some data for their current research. I readily agreed because I wanted to acquaint myself with Oregon.

I soon discovered that their research had to do with water deficit in trees, an area of physiology which at that time held little interest for me. They were measuring the water deficit of needles using a vapor equilibration technique which was not only quite tedious but took several days to accomplish as well. Dick had seen the P.F. Scholander et al. paper in Science and was excited about using the new “pressure bomb” technique instead of the vapor equilibration technique. He had contacted Scholander about how to obtain the appropriate instrument and was told that none were available; they had to be hand-made. The student was also eager to convert to the new technique because it would be directly applicable to his MS thesis research, so he offered to build the necessary device. The student was Brian Cleary.

The Forest Research Laboratory, where Professor Waring and I both worked, had a machine shop, but they had little experience in manufacturing complicated high-pressure devices such as was needed. The Physics Department, however, also had a machine shop which was used to manufacturing custom scientific devices. Brian made arrangements to work with the Physics Department machine shop to design and fabricate a “pressure bomb” using a diagram in the Scholander article as inspiration. The product was a complicated tangle of tubes and gauges and a heavy metal chamber and pressurized nitrogen bottle all connected together and strapped to a back-pack frame (for use in the field). But it worked, and Brian used it to collect the remainder of his data for his MS thesis.

In the process of completing his research, Brian and I became friends. I became more closely acquainted with the physiological aspects of his research and he became interested in working for a PhD degree in the area of the physiology of water in trees. We also had some long conversations about the pressure bomb and it’s future in research. Meanwhile Dick and Brian received several letters from scientists who also wanted to use a pressure bomb. They arranged for the physics shop to put together one or two additional instruments which were sold (at cost) to two of the interested parties. As additional requests piled up, the Physics Department decided that they were not in the business of manufacturing instruments commercially and refused to construct any more. About that time Brian and I attended a Society of American Foresters meeting and we decided to drive down to Medford together and share a hotel room while at the meeting. We discussed the pressure bomb the entire trip (we actually did attend several of the SAF sessions), and the pros and cons of getting into the manufacturing business ourselves. By the end of the trip we had agreed to form a partnership and commence building pressure bombs commercially. We also agreed to name the enterprise the “PMS Instrument Company.” This venture was to be an activity outside of regular university work and done completely on our own time. It was still necessary, though, to obtain permission to conduct an outside activity from the College of Forestry, which we did. We each put up $500.00 startup capital, designed the first instrument, obtained the necessary parts, and commenced putting our first instrument together in Brian’s garage. I continued my research with the university and Brian worked on his PhD research by day; we worked on Brian’s garage evenings.

Our chamber design featured a stainless steel chamber with 2-1/2 inch inside diameter cavity and with external triple-start coarse threads and a mating cover with a rubber seal. A #6 rubber stopper with a suitable hole up to 3/16” diameter was used to seal in the plant sample. A large test gauge indicated the chamber pressure and stainless steel valves controlled the chamber pressure. An external 2000 psi nitrogen tank supplied the necessary pressurized gas. The parts were mounted in an enclosed wooden cabinet about the size of a small suitcase, and quick-connect fittings were used to connect the instrument to the nitrogen tank. Before the instrument was even completed we had an order from the Weyerhaeuser Company for it. By that time most of our capital start-up money was consumed, but the proceeds from our first sale provided funds to buy parts for the next two instruments.

Despite no advertisement of our company or product, news of our pressure bomb spread throughout the scientific community by word of mouth and our orders started coming in. We made two instruments at a time at first but soon made them in batches of five. With each batch we incorporated small modifications and improvements in design as we gained more experience in putting them together and with using them ourselves. After producing about 20 wooden cabinet models we switched to a plastic (later fiberglass) suitcase-style, some of which contained a small pressure supply tank in the cover. Eventually, several different models evolved. We also constructed custom instruments for people with specific needs.

From the beginning we agreed to produce a quality instrument. We reduced cost as we were able but we did not take short-cuts in quality. It also helped that Brian and I both used a pressure bomb for our own research. We knew first hand and early on where problems existed with the instruments, and we took action to address those problems as soon as possible. Other companies have undertaken to produce competitive instruments, but the PMS models have remained the gold standard right from the start, partly because of the continuing improvements, inherent durability, and user-friendly characteristics of the instruments.

Joe Zaerr