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THMG015 – Advanced Metering

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In this episode, Mike and Bob discuss the advanced metering technologies available on the market today. Though there may be some heavy science behind the technology, we try to break it down to the basics.

Complete Show Notes

4:45 Photo Ionization Detector (PID)

  • Detect concentrations of gasses and vapors using UV light to ionize or strip away an electron
  • Once the ionization happens, the meter detects and measures
  • They’re very accurate – some can even go into the PPB range
  • PID measures anything flammable
  • Limiting factor is the IP or substance you’re trying to read – you can get bulbs that measure from 9-15 eV
  • Any bulb higher than that is very expensive and typically only has a 30-day warranty
  • These meters are calibrated to a single gas, so there’s a correction factor
  • These meters don’t destroy the sample – instead, they measure, then the gas recombines and continues on its way out of the unit
  • One way to remember whether you’re using a LEL or a PID is if you can see the substance – if you can see the substance, you want the PID; if not, try the LEL

7:55 Flame Ionization Detectors (FID)

  • Use combustion (i.e. a hydrogen flame) to burn a sample and produce an ion
  • These only react to organic compounds – don’t react with inorganic compounds like chlorine and ammonia
  • If you use the FID and PID together, they can identify (or at least classify) a greater range of products
  • How it works – the sample gas is exposed to a hydrogen flame, which ionizing the sample and creates ions. A negatively charged plate attracts the positively charged ion. The ion then moves through an electron field and is measured while moving through it

9:40 Thermal Imaging Camera (TIC)

  • Fire departments are familiar with these – there are hazmat specific models with more advanced capabilities
  • There are additional overlays to enhance viewing – allows you to detect minute changes in temperature, which provides more functionality
  • Use infrared energy to give readings on a screen – very useful to visually see a temperature gradient, such as an exo- or endothermic reaction or how full a drum is in the offloading process
  • Can’t see through reflective materials, even if the material is hot – you’ll only see a reflection
  • Must be pointed at a solid surface to take a temperature reading – if you shoot it at a flame that’s shooting in the air, the meter will read the ground or wall behind that flame

13:20 IR Thermometers

  • Measure infrared energy that’s being emitted from something
  • No visual display showing the data (similar to a TIC) – instead, you see a digital number
  • Relatively cheap, so they’re good for departments on a budget

14:30 Halogenated Hydrocarbon Meters (like TIF)

  • Halogenated hydrocarbons – hydrocarbons that have been joined with a halogen (i.e. chlorine, bromine, iodine, etc.)
  • Treat halogenated hydrocarbons as carcinogens
  • These are usually just click tracers that pinpoint a leak at a minute scale
  • Only provide a presence, rather than a numerical value – they use tones and beeps that increase in volume and speed when there’s a higher presence
  • Sensitivity can be adjusted; not intrinsically safe

16:25 Halogenated Hydrocarbon Meters (unlike TIF)

  • IR
    • The two most common models use IR absorption techniques
    • Older models use an IR source that shines IR into a tube – halogenated hydrocarbons absorb the light
    • The more absorption, the greater the concentration of a substance
    • Microprocessor autocorrects based upon the specific chemical you know you’re metering
  • NIDR
    • Newer technology is called NIDR, or non-dispersive infrared
    • These meters have two different chambers – one is a control chamber
    • They use a filter to narrow down specific wavelengths, allowing the meter to be very specific
    • Other common uses include measuring CO, CO2, and mercury

19:10 Gas Chromatograph (GC)

  • Chemical analysis instrument designed to separate chemicals in a complex sample
  • Use to measure contamination in the air, water, and soils
  • Typically aren’t used as field testing meters because they’re very expensive
  • They can separate and measure the components of the materials they’re measuring
  • They’re not very accurate due to impurities, and interference is a problem
  • Substances must have a boiling point below 300 degrees Celsius to measure quantitatively, and the samples must be salt-free

20:50 Ion Mobile (IMS)

  • Used in industrial settings to identify toxics and volatiles and in the field to identify explosives, WMDs, and drugs
  • Tough, dependable technology
  • How it works
    • A sample is brought into the meter and is charged or made into an ion
    • The sample then moves down a drift tube
    • The rate at which it moves down the tube is directly proportional to the ion’s size
    • The meter then assumes it’s one of the chemicals stored in its library
  • Requires very little maintenance and usually gives a few false positives – organic solvents are a problem
  • Isn’t meant to be used in every situation – you need to know when to use it because it goes off for everything

23:10 Mass Spectrometry

  • Analytical chemistry technique that helps identify the amount and type of chemicals present in a sample by measuring the mass-to-charge ratio and the abundance of gas-phase ions
  • Very sensitive type of CG – can even measure low PPM or PPB
  • Has the ability to break a compound down into fragments and then measure these fragments against a library to help identify an unknown
  • Not really applicable for use in the field – must be in a stable environment
  • Operator must be highly skilled

25:55 Surface Acoustic Wave (SAW)

  • Designed to detect nerve and blister agents
  • Uses special SAW micro-sensors that detect minute changes in the surface coatings of things that may be carrying WMD agents – a pump draws them into the chamber for analysis
  • Readings take around a minute to render
  • This technology probably isn’t sensitive enough to show trace readings of nerve and blister agents

28:00 Gamma Ray Spectrometer

  • Tests gamma source spectrum against a catalog to determine probable classification of actual isotopes
  • If the isotope isn’t in the library, the meter won’t be able to detect it
  • High-end models can measure multiple sources at once, read from further away, and see low energy and high energy signatures at the same time
  • Most of the meters have reach back capability – this refers to the ability to take the data and send it out to be read by lab professionals

30:55 Fourier Transform IR (Hazmat ID)

  • Type of infrared spectroscopy developed to overcome the limitations of dispersive instruments – dispersive instruments take light and manipulate it
  • Uses an interferometer that produces a different signal and allows for processing using all infrared signals
  • All IRs use light in the infrared area to give us information about the product
  • In Fourier transformation, light is sent down a tunnel and split into several separate paths – one goes to the product and another goes to a mirror
  • The mirror reflects back down the tunnel to the product
  • The mirror is important because it moves in tiny amounts, which causes the light hitting the mirror to put the product out of phase – this gives us information on the product
  • An interferometer measures the interference of the waves as it comes back off the product or goes through the product
  • Most infrared spectroscopy uses one signal, but this technology receives multiple signals (sometimes upwards of a thousand) – these are averaged and displayed for a smooth, consistent reading
  • Provides a quick response and is usually very accurate
  • Cannot see through glass containers or identify ionic substances, elemental substances, complex mixtures, aqueous mixtures, and some strong acids
  • This meter also uses reach back

35:15 Infrared Spectrophotometers

  • Infrared spectrometry uses a spectrum of light called infrared – we can’t see this
  • Then, it subtracts what it sees from what was there when it started to meter what was absorbed
  • Shoots a beam of light through a sample and measures what doesn’t come back – lays this out in a spectrum graph to show you what was absorbed and how much was absorbed
  • Some chemists may be able to read the spectrum and identify the compound down to individual isomers
  • While infrared spectrophotometers are field testers, they have trouble reading materials with water content
  • However, instruments compensate by removing the known spectrum for water – even then, it only allows mixtures of certain amounts of water

39:50 Raman Spectroscopy

  • Samples are irradiated with high-intensity light
  • Uses a single frequency, rather than a bunch – in other words, it reads one color rather than an entire rainbow
  • When this one color strikes the sample, some of the light changes color – it’s this change in light that the meter is looking for
  • Because each atom and molecule has its own set of color, we can graph colors or frequencies of light to determine what we have
  • Very good at finding toxic substances and pesticides
  • Can only do very limited mixtures, which tends to be an issue because most things found in the field are mixed
  • The frequency of light or color has a lot of energy that heats up dark objects and can initiate exposition of an unstable compound
  • If this is a possibility, reduce your sample size and lower the laser output to minimize this – some models allow you to set a timer so you can get to a safe location before it activates the laser
  • It’s possible for the laser to absorb the light to the point of ignition, so be careful
  • These meters don’t measure water and can go through glass, which are two big positives

43:15 Mercury Detection

  • Mercury is one of the most toxic elements on the planet – found in a lot of places, but it’s most common in old thermometers, barometers, electrical switches, and bulbs
  • Mercury detection meters use two main types of technology:
  • NDIR
    • Measure mercury vapor before drawing it into the optical chamber – usually measures at 253.7 nM
    • Cold vapor measurement method that’s extremely sensitive – accuracy is typically around 0.01 PPB
  • Gold Film
    • Sample moves across a gold film and adheres to it, which registers a change in resistance and a reading
    • You usually don’t see gold film types, as they tend to saturate more quickly and take a while to clear

45:25 Wet Chemistry

  • These usually have a strip that combines a bunch of chemistry tests into one convenient collection
  • You may see tests for reagents, chemical test strips, pH paper, and multifunctional test strips

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