These are the news starting 01 Jan 2018
Click here for the news of the previous years.

I continue the work on PM (fine particles) measurement, and assembled a station using the Nova SDS011 sensor (which detects PM2.5 and PM10) and a Raspberry PI 3 (with an added RTC) to read out the data and log them to the SD card. The most difficult problem was getting a correct Python script to work, as practically all examples found on the Net do not work with the (newer type?) of  SDS011. It seems that my model needs to be launched into measuring mode (leaving a sleep mode), and this command was probably not needed for older versions which run continuously when powered up. The script was modified so that the .csv data file has the date-time as name and every measurement line begins with a time stamp.

Upload of the Jun 2018 data into the  data archive.
28 Jun 18 I started a test series to measure fine particles (PM2.5, PM10) using an el-cheapio Chinese sensor board which holds the particle sensor (working by laser diffusion), a NDIR CO2 and T and RH sensors. The board sends its data as a continuous serial stream with about one line of data every 4.6 seconds. I use a Raspberry PI 2 with an added real-time clock as a datalogger (software is a very small Python script). A battery powerpack (20000mAh, number in picture has one zero too many) drives both components, and is itself continuous recharged by a USB power supply. The system is mounted in the Stevenson hut where our other gas sensors reside. A first check was very satisfying, so a longer one has been started today. A problem with the cheap particle sensors is that the airflow (by a small fan) is not constant (influenced by wind and pressure conditions) and that high air humidity tends to give very exaggerate readings. Our test will show how this applies to the AirMaster AM7 and if it survives outside exposure.

Using the Powerpack protects the assembly against power outages and allows to transport the running equipment (the Powerpack can drive it for 24 hours before going flat).

03 Jun 18 Upload of the May 2018 data into the  data archive.
01 Jun 18 Following a heavy storm last night, my Internet access is down. Upload of last month data will be made asap.
08 May 18 Raoul Tholl brought the WBGT system back to correct function (13:00 UTC). We will keep an eye on it....
07 May 18 There is a problem with the WBGT system: the wetbulb thermometer is dry, probably due to a fault with the pumping system which should keep the thermometer wet. As a consequence the calculated heat-stress is not correct.
04 May 18 1. There was an error in the first plot of air temperatures (conflicting left and right y-axis). This has been corrected (with some efforts as a wrong time format in the "previous days" graph of air temperature was missed). Thx to N. Harpes for pointing to this error!
2. This is the first day where our Cairsens NO2 sensors shows NO2 values different from zero. The peak NO2 at 07:00 about 18 ug/m3 seems plausible.
01 May 18 Upload of the April 2018 data into the  data archive.
28 Apr 18 1. The display of the WBGT heat stress as been restarted at 16:45, the sensors (actually the pump wetting the humid Pt100) this morning at ~08:00 UTC. Click here for a picture that shows how efficient humidifying is to lower temperature (see the split of blue and green lines after 08:00).
2. A check of the CAIRSENS NO2 sensors shows practically 0 ppbv concentration (lower than the limit of detection). So the quasi zero display of NO2 does not seem a fluke: our NO2 values are very small at Diekirch!.
19 Apr 18 1. There was an error with the "previous days" graphs of O3 and NO2; now ok (09:00 UTC)
2. The CAIRSENS NO2 sensor has a LOD (Limit Of Detection) of about 10 ppb ( = 20 ug/m3). So do not be surprised by quasi zero readings, as NO2 levels usually are low at Diekirch. You may read this test report.
18 Apr 18 Both CAIRSENS sensors are now on-line, using analog voltage data transmission which does not show the nasty electrical ground problem. The live page today_01.html has been slightly changed: the "AIR QUALITY" plots now show ground ozone (O3) calculated as the difference between the combined O3&NO2 sensor and the new NO2 only sensor; on the same graph the plot of NO2 will also be shown. All units are ug/m3, and the conversion factor between ppb (as given by the Cairsens sensors) and ug/m3 is 2 for both sensors.
Please be patient if some glitches remain...The combined O3&NO2 "AQ" data are in channel 16, the new NO2 data in channel 17 of the logger files (as today.dat). As ch.17 had no sensor during the first 10 hours of the day, the graphs show impossible values for this time span (due to Gnuplot's autoscale function).

Click here for a picture.

17 Apr 18 I installed this morning our second CAIRSENS sensor, the NO2 model (delivers into channel 17 of the logger). From a hardware point of view, everything runs smoothly, but there is a nasty probleme with the analog signals going into the logger. Probably again a common ground problem, either caused by a dual-port USB power supply or the common ground in the two 4-20mA loops. I will check this asap, and possibly try a classical voltage signal output for both sensors, instead of the4-20mA loop. Please ignore glitches and other disturbances in the graphs.
01 Apr 18 Upload of the March 2018 data into the  data archive.
30 Mar 18 A new paper by Yuan et al. citing meteoLCD authors F. Massen and E-G. Beck has been published in Atmospheric Measurement Techniques. See here or look at our "papers" website under "foreign papers".
01 Mar 18 1. Upload of the February 2018 data into the  data archive.
Attention: there are no data from 26/02 08:00 to 27/02 08:30, due to the logger breakdown. This is a very rare event in the more than 20 years of meteoLCD, but alas not an impossible one!
2. The plots of Air Quality now show in the title "good if < 200). This qualifier corresponds to the UK norm of combined O3 and NO2 concentration; if that number is below 200 ug/m3, the situation corresponds to the 2nd level of the "GOOD" (=green) category, which holds 3 levels.
27 Feb 18 1. The datalogger computer was unable to load it's system (XPe), no obvious cause found. Restarted at 07:28 UTC today.
2. There is a second much more severe problem: the datalogger has corrupted readings, probably caused by my yesterday tests with reading dual analog signals (voltage and intensity) of the Cairsens O3&NO2 into the logger (problem of channel overload from inexistent galvanic separation, obscure common ground problem....).
3. I downloaded all data from the logger, emptied memory, re-installed configuration and programmed to restart logging at 09:00. The first correct data (graphs and numbers) should be available at 09:45.
26 Feb 18 There is a breakdown of our datalogger computer, since this morning around 07:30 UTC. Will look at the problem tomorrow morning...Sorry!
19 Feb 18 The meteoLCD crew has written a short paper comparing our 2017 total ozone column measurements with those made at the RMI, Uccle (close to Brussels). Uccle is a world famous research facility for TOC measurements, and has one of the longest data series available. Our Diekirch measurements made with vastly less expensive instruments are quite satisfying. Read the paper here.
01 Feb 18 1. Upload of January 2018 data into data archive. Please read metadata (file header) very carefully!
2. Attention: this is the last month with [O3] readings from the O341M sensor, which will be shut down now. The overlap with simultaneous measurements by the CAIRSENS O3&NO2 allows a comparison of the two measurement series, and most important, about their temporal synchronicity. A quick check shows a very satisfying behaviour of the CAIRSENS device, so that we plan to add a second CAIRSENS measuring only NO2, which would give [O3] by simple difference between the two CAIRSENS readings.
A real serious investigation on the CAIRSENS sensor can be found here (with highlighting added).
11 Jan 18 1. Work on the "trends" section finished. Some future editing is probable, as some datasets for comparison (like Uccle's TOC at WOUDC) are still uncomplete.
2. A first quick comparison of the measurements of our new CAIRSENS Air Quality sensor and the old ozone sensor shows a quite satisfying correlation.
04 Jan 18 Work on the "trends" section has started. 7 parameters out of 13 have been updated. This is not a fast and quick automatically done procedure, but remains tedious work, so be patient waiting for the final update.
03 Jan 18 Installation of the new CAIRSENS O3&NO2 mini-sensor (09:30)

This electrochemical (amperometric) sensor measures the combined O3 and NO2 concentration, which we call AQ (for Air Quality). The new measurements are on channel 16 (the former NOx channel). Channel 17 (former NO) should be ignored!

Picture shows our Stevenson hut with the Vaisala CO2 and the Cairsens O3&NO2 sensors (click for full size).

Using this sensor is sort of an experience. Only time will tell if it lives up to its promises (no calibration needed, minimal maintenance, acceptable precision).

The graphs of today will be a bit messy!

The purchase of the new sensor has been financed by our sponsor AALCD (Amicale des Anciens du Lycée Classique Diekirch).

02 Jan 18 Upload into data archive of :
1. yearly Excel file with 2017 measurements and elementary statistics : 2017_only.xls
2. summary Excel file with statistics 1998-2017: meteoLCDstats_1998_2017.xls
3. Corrected/edited the "monthlys" worksheet of the 2016_only.xls file.
4. NOx/NO2 sensor from Environnement SA (AC31M) definitively shut off.
This is the end of our traditional atmospheric gas measurements using big and expensive equipement. The O341M sensor for ground ozone will continue for a couple of weeks to allow comparison with the new equipment, before also going into retirement!
01 Jan 18 1. The usual dogs-dinner in the 7days plot due to Gnuplot problems with handling previous and new year (the logger files do not contain the year number). This will be self healing in the the next 7 days.
2. Upload dec17.dat and (= all 2017 .dat files concatenated with headers, and zipped) into data archive.


Back Home