Are there any special care precautions that must be taken before or during transportation?
No special care is needed when transporting an EAD because it doesn’t have a working fluid.
Can I communicate with the EAD remotely?
Yes. The EAD has Aerosol Instrument Manager® software which can be used to collect and process data. A RS-232 serial cable is used to connect the EAD and the computer with the software. You can also write your own software using the communication commands found in the EAD manual.
Can the EAD detect very low concentration of aerosols, and how is the EAD different from a CPC?
Unlike the single-particle-counting CPC, the EAD measures the total charge of diffusion-charged particles using a high-resolution electrometer. The lower detectable limit of the total charge has to be above the noise level of the electrometer in the EAD. Because of the linear relationship between the charge of a particle and the particle size in the range from 10 to >1000 nm, the lower number concentration limit for the EAD depends on the size of the particles measured. For example, the lower concentration limit is 200 particle/cm3 for 50-nm monodisperse particles. Although the EAD has a wide dynamic range, it is not normally used to measure very low concentration of small particles. The CPC, however, is very accurate at low concentration.
Does the EAD need coincidence correction at high concentrations?
No. The EAD offers accurate measurements at high concentrations without the need for coincidence correction because the EAD measures the total charge of the diffusion-charged particles. For example, the EAD can measure up to 5 × 107 particles/cm3 for 50-nm monodisperse particles.
How does the EAD complement the Condensation Particle Counter (CPC)?
Both the EAD and the CPC are fast aerosol concentration detectors. When the two instruments are used together, the mean diameter of a monomodal aerosol can be calculated by dividing the diameter concentration measured by the EAD and the CPCs number concentration: Dmean (EADdiameter/CPCnumber)This feature gives the users a fast, simple, and low-cost option to have a rough idea about the aerosol size without having to use a Scanning Mobility Particle Sizer™ Spectrometer.
Is the EAD suitable for fast-changing measurements?
The EAD is highly suitable for studies of ambient or emission-related aerosols, especially for tracing fast-changing events and studying aerosol dynamics. The Aerosol Instrument Manager® software and the display of the EAD update once per second. It is possible to set the data transfer rate up to 3.75 readings/sec using customer-written software.
What is the parameter measured by the EAD and why is it important?
The EAD measures a unique parameter called aerosol diameter concentration, a property of ultrafine aerosol particles that is most promising to correlate with their adverse health effects. The aerosol diameter concentration in [mm/cm3], also called total aerosol length (d1)*, is defined as the length of a chain with all particles from 1 cm3 of measured aerosol lined up on the chain. Hence, the EAD measurement falls between number concentration (d0) and surface area (d2).Continuous measurements of aerosol diameter concentration are thought to provide a better estimate of surface area deposition in the lung than the number concentration or mass of particles.(*EAD measurements actually respond to d1.13, very close to d1.)
Why is the diffusion charger unique in the EAD?
The Model 3070A EAD uses a patented “counter-flow” diffusion charger, also called “corona-jet” diffusion charger (US patent No. 6,544,484). In the EAD, the ions generated by the high-voltage needle are carried by clean air into a mixing chamber to mix with the aerosol flow. Particles are separated from direct contact with the high-voltage needle, which reduces particle losses and improves charging efficiency.