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 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
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
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)
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
Environmental Operating Conditions Temperature: 0 – 40°C (32 – 104 °F) RH: 0 – 100% RH non-condensing
  • 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

Droplet offers a three-year service plan to ensure that your SP2 continues to deliver high-quality data. This plan locks costs upfront at the time of funding application and covers annual calibration, alignment, cleaning, wear-item replacement, calibration documentation, and shipping. Specific services provided for SP2 include:

  • Shipping to and from Droplet facility for service
  • Incoming instrument evaluation and health check
  • Full system leak test
  • Filter check
  • Laser power and beam image tests
  • Power supply and electronics verification
  • Voltages set and verified
  • Laser driver calibration
  • Optical cleaning
  • Crystal and output coupler alignment
  • Laser alignment
  • Mode match optics alignment
  • O-ring replacement
  • Hardware replacement
  • Mode aperture alignment
  • Optical cavity and jet-slide alignment
  • Flow measurements and coefficients calibration
  • Laser temp set point calibration
  • Current set point calibration
  • YAG reference monitor calibration
  • Pump burn-in
  • Laser burn-in
  • Scatter detector alignment
  • Split detector alignment
  • Baseline voltages set and verified
  • Sizing & distribution calibration using Aerosol Generator and PSLs
  • Sizing & distribution calibration using DMA and black carbon
  • Ambient distribution
  • Zero count test
  • Data processing
  • 100% unit functionality test
  • Software, firmware, and antivirus update
  • Calibration data, Calibration Report, Certificate of Calibration provided

Talk to an expert

Speak with one of our scientists or experts at Droplet Measurement Technologies today to discover solutions that can power your research.

Let's Talk