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​Model 651

Ultrafine Particle Monitor




  • Real time, continuous ultrafine particle monitoring
  • Water-based condensation with laser detection
  • Standard 19" rack mountable chassis
  • Long autonomy period - 30 day maintenance interval
  • Automated health and status monitoring
  • 7 nanometer detectable particle size
  • Sampling interval down to 1-second
  • Internal Data Storage
  • Communications via USB, Ethernet, or RS232
  • Remote monitoring, data retrieval, and control


Please refer to operations manual​ for maintenance instructions.


07506C Manual, Operation, M651.pdf651 Manual2046 KB
651_Literature_RevA.pdf651 Specification546 KB
ESD Fundamentals - 04786.pdfFundamentals of Electro-Static Discharge (ESD)216 KB
SAL000071B-CN 651.pdf651规格 (Chinese Specification)815 KB


 Principle of Analysis
Water-based condensation particle counter
0.001 to 106 particles/cm3
 Particle Size Range (D50) Range
 0.007µm (7nm) to ~3 µm​ 
 Particle Concentration Accuracy
 +/-10% at 106 particles/cm3
 Measurement Averaging Time
1 to 3600 seconds (1 hour)
Response Time
<3 seconds to 95% in response to concentration step
change (high flow mode: 3 lpm);
<5 seconds to 95% in response to concentration step
change (low flow mode: 0.6 lpm)
 Flow Rate
0.6 +/- 0.06 lpm (low flow mode) ;     
3.0 +/- 0.3 lpm (high flow mode)
 Environmental Conditions 
10 – 38ºC (50 – 100ºF) non-condensing;  (Recommended: 20 – 25ºC)
Power Requirements 100-240 VAC, 50/60HZ, 145W max 
Analog Output Ranges 0-4V proportional to log concentration
 User Interface
Color touchscreen display
Ethernet, RS232 and USB
Dimensions (HxWxD)
8” x 19” x 12” (203 x 483 x 305 mm) 

Specifications are subject to change without notice.
All specifications are based on constant conditions.​

22 lbs (9.9kg)


Ultrafine particle (those less than 100nm, or 0.1µm in size) are produced through combustion activities and are persistent in all ambient air. Concentrations of these tiny particle can be very high near emissions sources (for example, near busy roads), and both acute and chronic exposure are believed to lead to health problems. As part of the new US EPA near-road ambient monitoring network, ultrafine particles (UFPs) will be monitored to determine concentration levels and further study health effects related to exposure.

The Model 651 Ultrafine Particle Monitor provides a simple and reliable solution for the real time monitoring of UFP concentrations in ambient air. The instrument uses a condensation particle counting technique, using water as the condensing fluid followed by laser detection. UFPs down to 7nm in size are detected, with time resolution down to 1-second. Sample collection, preparation, and analysis occur continuously, with a routine maintenance interval of 30 days.

The Teledyne API Model 651 Ultrafine Particle Monitor is an ideal solution for today's routine ambient air quality monitoring applications.