toggle menu

Ceilometer CHM 15k „NIMBUS“

The LIDAR-based cloud height sensor / ceilometer CHM 15k is prepared to work throughout the year and in any climate

The Lufft CHM 15k has a double-walled housing combined with integrated fan and automatic heating system. Thus it provides reliable protection against misting, precipitation, freezing or overheating.

Exact results due to high sensitivity!
Reliable and accurate results at any time of the day or night are ensured by the use of long-life laser sources, filters with narrow bandwidth and high-sensitivity photodetectors.

  • Aerosol backscatter profile, cloud base height, cloud penetration depth, aerosol layer height, cloud cover, vertical visibility, Sky Condition Index
  • Optical (LIDAR)
  • Measuring range up to 15 km (50,000 ft), optimized detection of several cloud layers, simple eye-safe operation, service-friendly modular device design, various data telegrams including raw data
  • RS485, LAN, RS232 oder Modem V.21, V22
  • 8350.00, 8350.01 incl. 8350.MOD, 8350.10, 8350.03
Request a quote or advice

Example of use of the Cloud Height Sensor / Ceilometer CHM 15k

The CHM 15k is a simple single-shaft backscatter Lidar cloud height sensor or ceilometer. Within its measuring range of up to 15 km, it reliably detects several cloud layers, cirrus clouds and aerosol layers. The ceilometer is therefore often used for the following applications and events:

  • Observation of up to 15,000 m high cirrus clouds
  • Creation of aerosol backscatter profiles
  • Determination of the boundary layer height
  • Precipitation measurement
  • Cloud cover detection
  • Fog detection
  • To determine the vertical visibility

Our clients include public and private weather services, environmental agencies and national and international airports.

Learn more about it int the Lufft CHM 15k brochure

You need support or advice? Get in contact with us!

Product variants - Ceilometer CHM 15k „NIMBUS“

The laser-based cloud height sensor Ceilometer CHM 15k „NIMBUS“  is available in different product variants:

  • Ceilometer CHM 15k „NIMBUS“ (Article no. 8350.00)
  • Ceilometer CHM 15k „NIMBUS“ with DSL modem (Article no. 8350.01)
  • Ceilometer CHM 15k „NIMBUS“, US version (Article no. 8350.10)
  • Ceilometer CHM 15k „NIMBUS“, housing color red-white (Article no. 8350.03)

All versions are available with or without Battery Back-up (8350.BAT).

Advantages of the Cloud Height Sensor / Ceilometer CHM15k

The Lufft CHM 15k is a LIDAR cloud height sensor based on a single wavelength backscattering technique. It detects various cloud layers (max 9), cloud penetration depths, issues the Sky Condition Index, vertical field of view (VOR), aerosol layer heights, boundary layers and aerosol backscatter profiles with a range of up to 15 km.

The sensor achieves excellent signal quality thanks to its stable wavelength and its Nd:YAG narrow-beam microchip laser operating in the 1064 nm range. In addition, its technology enables efficient daylight suppression and reduces temperature fluctuations to a minimum.

Due to its pulse energy and laser frequency it is eye-safe and classified as a 1M laser product.

Moreover, the CHM 15k features a user-friendly design that enables unattended, continuous operation.

The CHM 15k is a state-of-the-art solution for today's diverse requirements of atmospheric research. It is suitable both as a sophisticated aerosol research instrument and as part of a large measurement network.


Further details in the Lufft CHM 15k  brochure

You need support or advice? Get in contact with us!

In addition to the PlayStore, our App is available for download via HTTP in APK format.

How to install Android APK from other sources than Google Play Store:

Find out here

Download the App

Android APK from other sources than Google Play Store - CHSIM
Brochure - Lufft - Ceilometers CHM 8k and CHM 15k
Brochure - Lufft - Cloud Height Detection (DE/EN)
Certificate IEC60825
CHM15k Lasersystem Certification
Certificate IEC61010
TÜV Certification - CHM15k, CHM8k
EU declaration of conformity - CHM15k
EU declaration of conformity - Lufft CHM15k
Firmware - Lufft - CHM 1.130_550
Please check compatibility via CHM web interface.
Firmware - Lufft - CHM 1.130_552
Please check compatibility via CHM web interface
Manual CHM15k - Chinese
Manual CHM15k - Croatian
Manual CHM15k - EN
Manual CHM15k - EN
Manual CHM15k - French
Manual CHM15k - Hungarian
Manual CHM15k - Portugese
Manual CHM15k - Spanish
Manual CHM15k – Dutch
Manual CHM15k – Italian
Video - CHM15k: Applications with the Cloud Height Sensor CHM15k
Video - CHM15k: Technical Introduction of the Ceilometer CHM 15k
Download as PDF
Measuring principle Lidar (optical, time of flight)
Measuring parameters
Description Aerosol backscatter profile
Range 5 ... 15,000 m (16 ... 50.000 ft)
Time resolution 2 ... 600 s
Range resolution 5, 10, 15 m
Quality and auxiliary values External and internal temperature, window status, laser status, receiver status
Target parameters
Quantities given in layers Cloud base height (CBH), Cloud penetration depth (CPD), Aerosol layer height (ALH)
Number of layers 1 - 9 layer (programmable);
3 layer preset
Distance measurement accuracy against hard target Greater of ±5 m (±16 ft) or ±0.2%
Additional quantities Cloud cover in octas (WMO 2700), Vertical visibility in m, Sky condition index
Standard interfaces RS485 (ASCII communication)
LAN (Web-Interface, (S-)FTP, NetTools)
Optional interfaces DSL modem, RS232 for service
Electrical parameters
Power supply 230 VAC or 115 VAC, ±10 %
Power consumption 250 W (Standard)
800 W (in maximum heating mode)
UPS functionality (opt.) Internal backup battery for electronics >1 hr
Laser-optical parameters
Light source Nd:YAG solid state laser
Wavelength 1064 nm
Pulse energy 7 µJ
Pulse repetition frequency 5 - 7 kHz
Filter Bandwidth 1 nm
Field of view receiver 0.45 mrad
Operating Safety
Environmental compliance ISO 10109 - 11
Laser protection class 1M, IEC 60825-1:2014; complies with 21 CFR 1040.10 except for deviations pursuant to Laser Notice No. 50, dated June 24, 2007
Protection level housing IP65
Electrical Safety EN 61326 - 1 Class B
Certifications CE
115 VAC version compatible with FCC/ CSA
International standards Complies with ICAO frangibility requirements
Operating Conditions
Temperature range -40...+50 °C
Relative humidity 0 ... 100 %
Wind 55 m/s
Dimensions 500 x 500 x 1550 mm
Weight 70 kg (130 kg incl. Packaging)
Download as PDF

CHM 15k: 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.

CHM 15k: 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

CHM 15k: How to find/choose correct firmware version corresponding to your hardware version

A new firmware version for the CHM 15k comes in two hardware-dependent variants: 

  • Firmware version 0.xxx_550 (e.g. 0.743_550)
  • Firmware Version 0.xxx_552 (e.g. 0.743_552)

The version 0.735_552 and all subsequent versions X.XXX_552 apply to newer CHM 15k devices which have been built since June, 2015. From the installed firmware version 0.733 on, you can find the right update version through on the CHM web interface.

For devices with firmware versions before 0.733, you can recognize the compatibility by means of the OS version (web interface --> device tab "firmware"):

For OS: 12.12.1 please use the firmware version 0.735_550 and for OS: 15.06.1 the firmware version 0.735_552.

If you have uploaded the wrong version accidentially, the status bit 12 is set. You can install the appropriate version again.

You can find the new firmware in the download area of the CHM 15k product page.

CHM 8k / CHM 15k: Does the device have a window contamination control?

Depending on the degree of soiling of the windows, a corresponding NetCDF variable (state_optics) is reduced from its original value of 100. A warning is issued when a certain limit value (70) is reached and the status code of the device is changed. This can be used as a recommendation for cleaning the windows.

CHM 8k / CHM 15k: Is it possible to get the device-specific overlap data for own calculations?

The overlap data corresponding to your device can be sent to you in the form of a file. Please contact us at

CHM 15k: What is the minimum distance between two devices in order to prevent mutual interference of the backscatter signals?

A distance of 50 cm between the instruments is sufficient, provided that the levelling screws in the base of the instrument ensure a mutual tilting of 0.5°.

CHM 8k / CHM 15k: How should the device be installed in relation to the sun?

How should the device be installed in relation to the sun?

The device side with the door should face south. In case of high solar radiation (south of 35° northern latitude), the device should additionally be tilted to the north via an adapter angle in order to keep the influence of solar radiation as low as possible.

This applies to the northern hemisphere. For the southern hemisphere, the opposite cardinal directions apply.

Please consider that measurements against the sun are not possible for an optical measuring device.
We offer corresponding angle adapters as accessories. Please feel free to contact us on this subject.

CHM 8k / CHM 15k: Can the status of the NTP query (time server) be verified?

As of firmware version 1.020, the web interface / page "Process Status" displays the server name, status of availability, current time offset, query interval, etc.

Note: If the time offset exceeds 1000 s (approx. 17 minutes), the iterative adjustment via the NTP protocol no longer works. The time must then be set manually, e.g. via the web interface, or the device must be restarted. The time is newly set at system startup when the NTP server is available.

CHM 8k / CHM 15k: What are the maximum cable lengths for the CHM 8k / CHM 15k?

The standard cable length for power supply and data transfer is 10 m. Longer cable connections are also possible. Please feel free to contact us for this.

CHM 8k / CHM 15k: In which cases does the case fan start?

When the device is started: for typ. 2 minutes, in case of dirty or wet panes as well as detected rain, for cooling at interior temperatures > 39 °C and per default every hour for removal of dust, pollen, etc. To minimize possible noise pollution, the activation of the fan can be limited via the BlowerMode parameter. Please pay attention to the correctly set parameter TimeZoneOffsetHours for compliance with possible night/rest times. Further information can be found in the manual, chapter 8.1

CHM 8k / CHM 15k: Why is Cloud Cover -2 displayed after starting the device?

For the calculation of the cloud cover at least the last 30 minutes of the measured data are used. Without the complete data (temporal) no calculation is possible -> "-2" is output.

CHM 8k / CHM 15k: What should be considered with regard to the use of SD cards?

Cards with a memory capacity of up to 32GB can be used from Speed Class 10 on. We recommend industry standard. Formatting must be done with FAT32 file system. Formatting via the web interface is possible and recommended. To change the card, the device must be shut down and externally disconnected from the power supply and secured against being switched on again.

CHM 8k / CHM 15k: Why is there a delay in displaying data in the web interface or why is it only displayed after clicking "Update"?

Automatic display has been disabled on the Viewer page to keep traffic low on low data rate connections. The other data is updated every 15s. On the Process Status page, the data is updated every 60s.

CHM 8k / CHM 15k: How should the NetCDF variables "time" and "range" be interpreted?

"time" means the end time of the measurement

"range" means the beginning of the range

CHM 8k / CHM 15k: Can the device be operated, restarted or deactivated remotely?

The device can be configured, restarted and shut down conveniently and password protected via the RS485 interface as well as via LAN/WAN and web interface.
Both the firmware and the operating system are restarted via 'restart system'.
Via 'shutdown system' the system is shut down and must be switched on again for a restart on site. Please take this into account, especially if the device is not installed in the immediate vicinity.
Please find a detailed description of the functionality in the manual.