Single Particle Soot Photometer

The SP2 is Droplet’s premier instrument for direct measurement of black carbon in individual aerosol particles. The SP2 delivers unmatched detail about black carbon particles, including mass, size, heat of vaporization, and coating – critical information for characterization of pollution sources, accurate description of optical properties, and prediction of health effects.


Enhance model effectiveness by capturing variances in black carbon make-up with single particle detection.

Measure black carbon independently of particle mixing state with Nd:YAG intracavity laser-induced particle incandescence (LII).

Get full characterization of each individual black carbon particle (mass, size, heat of vaporization, and coating) with simultaneous measurement of incandescence and light scattering.

Detect black carbon at concentrations below 10 ng/m3 with dual gain stages – enabling full characterization in the cleanest environments.

Control the instrument, display data, and log data with UI software and a user-friendly virtual instrument panel.

Perform advanced data analysis and create journal-quality reports with a comprehensive toolkit.

Laser incandescence and particle light-scattering

  • Nd:YAG intracavity laser-induced particle incandescence (LII) measures black carbon independently of particle mixing state.
  • Single particle incandescence is measured and correlated to black carbon mass
  • Single particle light scattering is measured and used to indicate particle size, non-BC containing aerosol number, and mass concentrations.

Measured Parameters
  • Single-particle laser incandescence
  • Single-particle light scattering
Auxiliary Parameters
  • Temperature
  • Pressure
Derived Parameters
  • BC mass distribution as function of particle diameter
  • Particle number distribution as a function of particle size
Maximum Data Acquisition Rate 12,500 particles/cm3 at 120 vccm
Particle Size Range
  • Scattering: 150 – 400 nm diameter (this range encompasses the accumulation mode of most particles, i.e. range where most mass is found).
  • Incandescent: 0.07 - 100 fg; approximately 40 – 450 nm mass-equivalent diameter assuming a black carbon density of 1.8 g/cm3
Aerosol Medium Air, 0 - 40 °C (32 - 104 °F)
  • Intracavity Laser: 1064 nm Nd:YAG
  • Pump Laser: 808 nm
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 within a single enclosure
Minimum Black Carbon Detection Limit
  • 0.07 fg/particle
  • No lower concentration limit
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
  • Four 0-5V analog inputs (BNC)
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)
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, expandable with external storage.
Power Requirements
  • 100-240 VAC
  • 50/60 Hz
  • 330 W
  • Instrument: 48 cm W x 61 cm L x 26 cm H
  • Pump: 20 cm W x 25 cm L x 10 cm H
  • Monitor: 37 cm W x 22 cm L x 39 cm H
  • Instrument: 26.1 kg
  • Pump: 3.4 kg
  • Monitor: 3 kg
Environmental Operating Conditions
  • Temperature: 0 – 40°C (32 – 104 °F)
  • Humidity: 0 – 100% non-condensing
  • Altitude: up to 40,000 ft
  • Beam scan camera and software
  • YAG optics kit (spare YAG crystal and output coupler)
  • Laser alignment bench
  • Nebulizer for liquid samples with optional auto- sampler
  • Aircraft Aerosol Inlet

The Lifecycle Care Program ensures SP2-D integrity and performance vital to your research mission for 3 years or 3 calls (whichever comes first). When conducting complex and time intensive laboratory or field measurements it is critical to avoid down time, and ensure data collection accuracy. The program consists of 3 key deliverables for each year or call:

  • Instrument Logistics
  • Instrument Integrity
  • Instrument Performance

Lifecycle Care Program Includes:


  • Shipping to and from Droplet Measurement Technologies facility
  • Customs handling, including CARNET ATA if required


  • Incoming instrument evaluation and health check


  • Software and firmware validation
  • 100%-unit functionality test
  • Calibration data
  • Calibration report
  • Certificate of calibration

At times, our technician might discover an instrument issue, which might not be covered by the Lifecycle Care Program or by our product warranty. In such case we will reach out to you with a service & repair estimate to allow you to provide us with the next steps of action.