Metrologists measure things professionally. But what does that mean? And why is that important? These are some things I answer in today’s post in a simple and applicable way.
When I tell people I’m a junior legal metrologist, the first question I get is “So you work with the weather?” Erhm, no. That would be a meteorologist, and while part of their job is measuring things with respect to environment and weather, I work with units and the science of measurement as a concept.
That’s not a great answer, because it still doesn’t really tell you what I do. (Truth be told, I didn’t fully understand what I did until about a week in.) Let’s start really general, and then move in to details.
The What: Metrology is the study of measurement, so metrologists are people who study and work with measurement.
The Application: Grocery scales, electricity meters, gas pumps, thermometers, pressure gauges on natural gas lines; all of these things are measurement devices that everybody uses and relies on every day, so these things must be accurate and reliable for fairness in industry for consumers and companies alike. Metrologists are the people who make sure this technology is accurately and reliably doing its job, as well as adopting newer and better technologies.
Wait, thermometers and grocery scale technology changes?
You bet! All these technologies have components and sensors that degrade through aging, or react differently in different environments. So better technologies are ones that are more impervious to aging or outside effects.
– Modern, high-precision pressure gauges often rely on piezo crystals to provide a proportional electrical resistance to how much pressure is applied to them. These crystals warp over time and the internal software coefficients have to be changed to give accurate readings.
– All electronics act up in extreme temperatures. This is especially important when designing a gas pump sensor that’s supposed to work in Ottawa, where the temperatures go from -40ºC in the winter to +40ºC in the summer.
– Even old-school measuring devices misbehave over time, like the spring-loaded scales in grocery stores that you put your bag of apples on: the spring stretches over time, so the accuracy of the reading will drift.
The People: Most people in industrial-level metrology are engineers, physical scientists or highly trained technologists. You have to be someone who likes hands-on work, who’s good with troubleshooting and thinking mechanically, and who has an inclination for numbers. You’re working with a lot of misleadingly similar data; you have to be able to predict trends and extract meaning.
The Job: As an example, I’ll describe a typical day in the pressure lab. I will get a device from a client, often a certified natural gas provider like Gaz Métro or Fortis Alberta, and it’s usually a pressure gauge or a barometer that is used to inspect pipelines in homes or in the field. I will connect this device to a highly controlled pressure source (or a “standard”, which is what we call all of our reference devices in all the labs) and run the device up and down the range it’s rated for while I compare the reading to our controlled readings. I then put this data into an Excel spreadsheet to analyze the error and the uncertainty on the reading, which in turn determines if the device is giving readings that are within the legal accuracy requirement for industry. If it passes, I will draft a certificate and the data is then reviewed by my boss (the gas lab manager) and the gas lab senior engineer, where it is usually approved and then the device is certified and sent back to the client. If it doesn’t pass, it’s my job to troubleshoot why it’s not working. Sometimes there’s a loose component in the circuitry or a leak in the device; often all I need to do is reprogram the coefficients. But if the device is damaged, or too old, or too unpredictable, it will fail indefinitely and can’t be used.
* * * * * * *
Beyond Industry: Our standards come from NRC, where metrologists (usually with Ph.Ds in science or engineering) are studying units like time (with atomic clocks), length (with the speed of light), intensity (with single-photon detectors) and other quantities like pressure, temperature, volume, and mass to extremely precise values. Other labs around the world do the same and compare their results in annual conferences; the global standard is generally the average value. A notable exception is the SI unit of mass, where a silicon sphere in France is universally understood to be the perfect kilogram. These extremely precise units are important in an increasingly precise scientific world, where nanotechnology, microgravity and laser delays need to be measured with as close to perfect certainty as physically possible.