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Home Products Black Carbon Single Particle Soot Photometer Single Particle Soot Photometer (SP2)

Single Particle Soot Photometer (SP2)

Single Particle Soot Photometer (SP2)

Droplet Measurement Technologies' SP2 - The only instrument in the world that directly quantifies the black carbon (soot) in individual aerosol particles.



  • Pollution characterization
  • Air quality and visibility
  • Atmospheric and climate research
  • Health effects studies
  • Combustion emissions
  • Biomass burning

The SP2's high sensitivity, fast response, and specificity to elemental carbon make it the premier instrument for characterizing air pollution sources and documenting thin atmospheric layers of contamination. It is also ideal for measuring soot in snow, ice or water and for calibrating other black carbon-measuring instruments like the Aethalometer.

Video of the SP2 being used for ice core sampling.

  • Measures black carbon (soot) mass in individual aerosol particles
  • Uses Nd:YAG intracavity laser-induced particle incandescence (LII), a technique that measures black carbon mass independently of particle mixing state and hence yields more accurate results
  • Detects black carbon mass at minute concentrations (below 10 ng/m3)
  • Measures particle optical size using light-scattering
  • Counts up to 25,000 particles/sec (12,500 particles/cm3 at 120 vccm)
  • Provides full data recording of each particle event
Measured Parameters Single-particle laser incandescence
Single-particle light scattering
Auxiliary Parameters Temperature
Derived Parameters BC mass distribution as function of particle diameter
Particle number distribution as a function of particle size
Maximum Data Acquisition Rate 0 – 12,500 particles/cm3 at 120 vccm (0 - 25,000 particles/sec; concentrations can basically increase until particles become coincident)
Particle Size Range Scattering signal: 200 – 430 nm diameter (this range encompasses the accumulation mode of most particles, i.e. range where most mass is found).
Incandescent signal: depends on particle density, but 70 – 500 nm mass-equivalent diameter assuming a black carbon density of 1.8 g/cm3
Aerosol Medium Air, 0 - 40 °C (32 - 104 °F)
Lasers Nd:YAG Laser: 1064 nm, 3 MW/cm2 intracavity circulating power
Pump Laser: 808 nm, 4 W
The pump laser can be controlled either through the SP2 software or through the touch-screen on the SP2 front panel.) 
Sample Flow 30 – 180 volumetric cm3/minute (typically 120)
Flow Control Electronic flow control with a laminar flow element (LFE) and a solenoid valve
Pump Two single-head diaphragm pumps encased in a box
Minimum Black Carbon Detection Limit
  • 10 ng/m3
  • 0.3 fg/particle
Calibration DMT recommends calibrating the SP2 every six months and/or before and after every field campaign.
  • The incandescence measurement is calibrated to black carbon mass using DMA-sized Aquadag, fullerene soot or glassy carbon. (DMA refers to differential mobility analyzer, used to extract particles of a single electrical mobility size from a polydisperse aerosol.)
  • The scattering measurement is calibrated to particle size using monodisperse polystyrene latex (PSL) spheres or DMA-sized ammonium sulfate.


DMT offers free software that automates much of the calibration process. The Probe Analysis Package for Igor (PAPI) assists the user in loading, consolidating, and analyzing calibration data files. 
Routine Maintenance Weekly: 
  • Refreshing or replacing the desiccant in the drying cartridge on the purge line 
  • Conducting PSL size check to monitor laser power


Monthly and around field campaigns:
  • Conducting zero check with high-efficiency filtered air sample


Annually (more frequently for high-BC environments):
  • Checking calibration of the laminar flow element on the sample inlet
Recommended Service      Annual cleaning and calibration at DMT service facility 
Front Panel Display
  • System power switch
  • 2 USB 2.0 ports
  • 1/8 in. Swagelok® sample inlet
  • Laser ON/OFF indicator light 
Rear Panel Connections
  • Keyboard port
  • Mouse port
  • VGA and HDMI monitor ports
  • Ethernet port
  • 2 RS-232 communications ports
  • 4 USB 2.0 ports
  • eSATA port
  • ¼ in. Swagelok® purge line
  • ¼ in. Swagelok® exhaust line
  • Exhaust vents
  • System and pump power connections 
Computer System
  • On-board Intel®Core™ i7 CPU
  • 8 GB RAM
  • 750 GB hard drive for data storage
  • NI PCI-6133 DAQ interface card
  • NI PCI-6259 housekeeping data card
  • User interface via standard keyboard, mouse, and 19” monitor (included)
Software SP2 Executable program written in LabVIEW 
PAPI program written in Igor 
Data Storage Capacity Depends on number of particles; at a concentration of 1,000 #/cm3 and a standard flow rate of 120 volumetric cm3/minute, the SP2 computer has the capacity to store 56 hours of continuous data 
Communications Output Gigabyte Ethernet interfaced through an Intel® PC82573V PCIe GbE controller 
Power Requirements SP2: Universal Voltage
External Pump: 30 W
Dimensions SP2: 48 cm W x 61 cm L x 26 cm H 
Pump: 20 cm W x 25 cm L x 10 cm H
19" Monitor: 37 cm W x 22 cm L x 39 cm H
Weight SP2: 26.1 kg
Pump: 3.4 kg
19" Monitor: 3 kg
Shipping Container Durable Atlas Case Corporation ATA Transit Case that conforms to the Air Transport Association’s Specification 300 Category 1 standards
Environmental Operating Conditions Temperature: 0 – 40°C (32 – 104 °F)
RH: 0 – 100% RH non-condensing

Specifications are subject to change without notice. The SP2 is a Class I Laser Product with U.S. Patent # 5,920,388, exclusively licensed to DMT.