QuadraTherm 640i Insertion Thermal Mass Flow Meter

The development of an industrialized metal-sheathed sensor in the early 80s was Sierra’s first big step, but Dr. Olin is a driven innovator, and this was only the begin- ning for someone who saw “Thermal Mass Flow” as his life’s work. Many successful innovations followed, but in 1999 Sierra experienced a major breakthrough with the introduction of their patented no-drift DrySenseTM thermal mass velocity sensor. Sierra engineers now recognized they were on the cusp of realizing Dr. Olin’s vision.

Realizing the Vision

Thermal technology, by its very nature, uses the physics of heat transfer and conser- vation of energy in a closed system to measure mass flow rate. This means that for a thermal mass flow meter to achieve the greatest accuracy, it must solve the First Law of Thermodynamics (Heat Energy In = Heat Energy Out) for each data point.

As you can imagine, solving the First Law in a flow instrument was no easy task.
By Dr. Olin’s own accounting, decades of “hard-nosed dedication to excellence” by himself and Sierra’s engineering team, years of testing, and his stack of yellow note pads over five feet high, jammed with his handwritten equations and designs, finally yielded the secret in the form of two revolutionary technologies—QuadraThermTM and iThermTM, now both patented worldwide.

The QuadraTherm Sensor

Traditional thermal sensors have two sensors-–one temperature sensor and one velocity sensor, each in a separate probe. QuadraTherm (the term “Quad” meaning “four”) introduces four sensors—three precision platinum temperature sensors and one patented DrySense mass velocity sensor. Performance improvements never before possible are gained as the QuadraTherm Technology isolates forced convec- tion (the critical variable for measuring gas mass flow rate) by calculating and then eliminating unwanted heat-transfer components, like sensor stem conduction, one of the major causes of false flow readings.

iTherm, the Brains Behind it

iTherm is the true “Brain” of the instrument and a revolutionary, living, learning algorithm set made possible by today’s hyper-fast microprocessors and QuadraTherm sensor inputs. iTherm manages changes in gas flow,

gas temperature and gas pressure, as well as outside temperature, via a comprehensive heat-transfer model. The result of iTherm is a proprietary, fundamentally different gas mass flow rate calculation using all pertinent variables for the most precise, stable and accurate thermal mass flow measurement possible.