Aerosol sensor welas® 1100

The welas® 1100 aerosol sensor for number concentrations up to 500,000 particles/cm3


Aerosolsensor welas® 1000

Aerosol sensor welas® 1100

The welas® 1100 aerosol sensor for number concentrations up to 500,000 particles/cm3

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The model 1100 aerosol sensors are equipped with a small measurement volume and are used for coincidence-free measurement with a max. number concentrations up to 500,000 particles/cm3.

Measuring range: 0.12 – 3.5 µm / 0.2 – 10 µm / 0.3 – 17 µm / 0.6 – 40 µm.

Functional principle:

welas® digital and Promo® digital are based on scattered-light analysis on a single particle. The particles to be measured pass through a T-shaped, optically delineated measuring volume that is illuminated by a white light source. This generates a scattered-light pulse whose level is a measure for the concentration.

The high size classification accuracy and the high size resolution are guaranteed by the following special feature:
  • White light and 90° light-scattering detection
    unambiguous calibration curve
  • Patented T-aperture technology for a T-shaped measurement technology
    no border zone error
  • New digital individual signal processing for the analysis of the scattered-light pulse
    coincidence detection and correction which enables measurement in up to 5 times higher concentrations

Example: the welas® sensor aerosol guide heatable up to 250°C (see variations)

Trouble-free and reliable measurement of large particles up to 40 µm in the sensor is guaranteed by the vertical aerosol duct at a high volume flow of 5 l/min and a large sampling tube diameter.

Size limitation of the optical measuring volume

The table below shows the theoretical minimum separation of the particles at a given number concentration.
At a number concentration of 103 per cm3 the optical measuring volume must not be larger than 1 mm3.


The customer can select a sensor with the appropriate measuring volume size depending on the concentration to be measured.

optisches Messvolumen welas Sensoren.jpg

For concentrations up to 500,000 particles/cm3 the welas® 1100 sensor with a small measuring volume is used. This ensures the smallest measuring volume such that only one particle ever enters the measuring volume. In low concentrations the model welas® 1200 with a larger measuring volume offers the advantage of a higher counting rate at the same number concentration.

Counting efficiency of the sensors
The welas® sensors are characterized by a particularly good agreement of counting efficiency and particle size resolution.
This means that the measurement results are highly comparable in terms of the number concentration and particle size measured when using different sensors.

Zählwirkungsgrad welas Sensoren, welas digital 1000 - Diagramm 2.png

Graph 1:
The welas® 1000 series of aerosol sensors is characterized by its very high counting efficiency starting from 0.12 µm!

Pressure-resistant and heatable aerosol sensors with a special cuvette for the variants P, H and HP

Special measuring cuvettes allow the use of the welas® aerosol sensors even under unusual measuring conditions. These are available:

  • heatable sensors up to 250°C; higher temperatures on request
  • pressure-resistant sensors up to 10 bar overpressure
  • sensors resistant against chemically aggressive media


  • Widest measuring range of 120 nm to 40 µm (4 measuring ranges selectable in one device)
  • Calibration curves for different refractive indices
  • Widest concentration range of 0 particle/cm3 up to 5 • 105 particles/cm3
  • Very high and reproducible counting efficiency rate starting at 0.12 µm (see Graph 1)
  • High temporal resolution down to 10 ms
  • Extensive PDControl and FTControl software
  • Strong, powerful external suction pump ASP 1000
  • Calibration, cleaning and lamp replacement can all be performed independently by the customer
  • Simple operation
  • Low maintenance
  • Reliable function
  • Reduces your operating expenses


Measurement range (number CN) 0 – 5 • 105 particles/cm3
Measurement range (size) 0.12 – 40 µm (4 measurement ranges)
Volume flow 1.6 l/min, 5 l/min (others on demand)
Thermodynamic conditions +10 – +40 °C, -100 – +50 mbarg
Light source Xenon high pressure lamp 75 W
Weight Approx. 19 kg
Cooling Air cooling
Power supply 115 – 230 V, 50/60 Hz
Dimensions 200 • 530 • 530 mm (H • W • D)


  • Determination of the separation efficiency of car interior filters, engine air filters, room air filters, compressed air filters, vacuum cleaner filters, cleanable filters, electrostatic precipitators, oil separators, cooling lubricant separators, wet scrubbers, cyclones and other separators
  • Isothermal and isobaric particle size and quantitative determination, for instance in the automobile, chemical, pharmaceutical and food industries
  • Analysis of fast, transient processes
  • Inspection of smoke detectors
  • Particle formation for cloud formation
  • Emission measurements
  • Immission measurements


Brief Description
Brief product description in two-pages as PDF
Product Description
Detailed product description as PDF


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