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CHM Simulator for Cloud Height Simulation

The Lufft CHM Simulator simulates the cloud height for the ceilometer CHM 15k in order to check its measurement accuracy.

The simulator has to be deployed on the top of the ceilometer covering the laser inlet. One of the five LEDs receives the laser impulse emitted by the ceilometer and, after a certain time has passed, sends an optical signal back to the ceilometer simulating it via the 4 other LEDs. The time span between receiving and sending the signal as well as the time of flight of the return signal going back to the ceilometer shall correlate with a signal of an actual cloud. The characteristics of this simulated cloud can be determined by using the included CHM Simulator Application. Using the app, which shall be installed on a standard android based tablet, the user can select the cloud height and depth according to its preference. The app communicates via Bluetooth with the CHM Simulator. Furthermore, the strength of the d.c. light/background light can be chosen in order to check how the ceilometer can manage disturbances caused by background light. The results of this ceilometer-check can be read out directly at the ceilometer instrument. Some of the results are also given out by the app (laser frequency) or can be accessed via the embedded UMB protocol.
  • The Lufft CHM Simulator is an on-site calibration equipment to check the measurement accuracy of the cloud height for the ceilometer CHM 15k
  • 8350.SIM, 8350.SIMc, 8350.SIMco
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Product variants - CHM Simulator

We offer a few variants of the CHM Simulator for simulation of cloud height:

  • CHM Simulatior - Scope of delivery: CHM Simulator App, CHM Simulator Adaptor Frame, User Manual (Article no. 8350.SIM)
  • CHM Simulator, incl. Case - Scope of delivery: CHM Simulator App, CHM Simulator Adaptor Frame, Case, Power Cable 10m, incl. cig plug connector (optional: 24V power supply), User Manual (Article no. 8350.SIMco)
  • CHM Simulator, incl. Case & Tablet - Scope of delivery: Tablet incl. CHM Simulator App, CHM Simulator Adaptor Frame, Case, Power Cable 10m, incl. cig plug connector (optional: 24V power supply),  User Manual (Article no. 8350.SIMc)
Brochure - Lufft - Cloud Height Detection (DE/EN)
Brochure - Lufft - Image brochure (EN)
Image Brochure with description of all Lufft market segments
Manual - Lufft - CHM Simulator (EN)
Video - CHM15k: Applications with the Cloud Height Sensor CHM15k
Video - CHM15k: Technical Introduction of the Ceilometer CHM 15k
Download as PDF
Power supply 10 VDC...28 VDC on the sensor
Power input Ca. 3 VA
Protection type IP54
Dimensions 110 x 200 x 100 mm
Weight 1.7 kg
Storage conditions
Admissible storage temperature -40...70 °C
Operating rel. humidity 0...95 % RH (non - condensing)
Operating conditions
Permissible ambient temperature -40...70 °C
Operating rel. humidity 0...100 % RH
Interface RS485, 2 wire, half - duplex, bluetooth
Housing Aluminium, plastic
Containing CHM - Simulator, CHM Simulator adaptor frame, 10 m power cable incl. cig plug connector (optional: 24 V power supply), user manual
Software CHM - Simulator App (available online at Google Play Store)
Download as PDF

CHM15: On-site calibration & on-site check of the calibration How to do? How often to do?

Lufft is offering a cloud simulator tool to check the instrument quality in field.

The simulator generates different light pulses and background light levels to test the detection unit and the data acquistion path of our CHM units. The starting point is the laser itself. The laser pulse is detected by the simualtor and time shifted LED pulses are generated. By comparision with the instrument specific production protocol the user can easily see differences in the calibration. The simulator takes a test time of 30 minutes in maximum and should be repeated once per year to verify the status of the system.

In case the instrument is showing an error or the results of the simulator are out of specs, the LOM (laser optic module) of the CHM instrument shall be exchanged. It can be repaired and recalibrated in lab.

Furthermore, on-site calibration in field can be done to achieve absolute backscatter values from aerosol layers. The absolute calibration can be done in two different ways:

1) comparision with another lidar instrument, which should have a sensitivity 10 times better than the ceilometer and should have at least the same range resolution of 5m.

2) clear sky calibration and specific rain cloud calibration ( both methods will be implented by the European Met services shortly. There is an ongoing project to deliver the algorithms. Please check: 

Advantage: The Rayleigh calibration and the cloud calibration method do not need additional equipment.

The on-site calibration takes 24 h to 1 week to be able to compare different cloud and aerosol layer situations. In a rainy season, in permanent low cloud, brown cloud or in foggy places the on-site atmospheric calibration might not work at all and our cloud simulator check of the lab calibration gives you the best result.

CHM15k: In which applications is the ceilometer CHM15k in use?

The View into the Sky - Applications with the Cloud Height Sensor CHM15k! Watch our webinar recording where we present completely different application scenarios, where our cloud height sensor CHM15k can be the sensor of your choice!

To the webinar recording: Applications with CHM15k