Laser precipitation monitor FAQs            Back to previous page

We hope this page provides you with useful information. Please do not hesitate to contact us to discuss your own application requirements.

(Q: = Question    A: = Answer)

Q:   What are the maintenance requirements?

A:    There are no maintenance requirements (an occasional cleaning of the windows once a year would be advised though).

Q:   What spare parts are required?

A:    There are no spare parts necessary for the LPM. Support for replacement parts is available for at least 10 years.

Q:   What is the warranty period?

A:    The sensors come with a one year warranty?

Q:   What is the delivery time?

A:    The standard lead time is 4-6 weeks ARO (After Receipt of Order).

Q:   Is there an RS-232 output available?

A:    No. The output is RS-485. However, many of our users use our RS-485 to RS-232 converter. This type of converter is readily available from electrical suppliers or Biral.

Also worth noting is that if you are just having a one to one comms link and do not need full RS-485 capability you can use a suitable RS-422 to RS-232 converter. In this case the commands and data are fine but the networking/addressing features of RS-485 will be missing.

Q:   I have an old computer to act as DAQ and a power supply. If I purchase the LPM and power and data cables is that everything I need to be up and running?

A:    Yes that is all you need with the exception of the RS-485 to RS-232 converter, assuming that you have an appropriate mast or structure on which to mount the LPM. The LPM comes with mounting hardware but no mast - please see the question below for more information on the mounting hardware.

Q:   Does it come with the u-bolts to clamp onto a scaffold-type pole?

A:    Yes. There is a clamping device to attach it to a mast of various diameters (it is a large diameter hose pipe clamp that uses a screw to tighten or loosen the clamping device to the mast. The clamping device is basic but as long as you are not going to move it around too much from one location to another (requiring frequent tightening and loosening) then the supplied free clamp will be fine.

Q:   Is any special software needed on the DAQ machine to record the data?

A:    No. Any terminal emulation should work and we have tested it with the free MS HyperTerminal or older MS Terminal programs supplied with MS Windows Operating Systems. The data is ASCII and semi colon delimited so it can easily be imported into MS Excel or similar programs for analysis or viewed as is by the user.

There is optional software, the LMNView software, which allows you to connect locally or remotely over a network (intranet) and easily view the data according to date time using a tree structure. This plots the data and shows you spectrum information on particle types as well as fixed field information on performance of the unit. However if you are well versed in MSExcel you can easily import the same information and plot it from the ASCII files with some work.

The LMNView software is not mandatory and if you are on a tight budget it can be added if so desired at a later date.

Q:   What power and data cables are required?

A:    There are cable glands for the associated cables on the base of the LPM and this includes one for a power cable and one for a data cable. The cable requirements are the same for data and power and we quote the generic Thies cables which are rated for ranges of low DC to 230 V mains ie:

• 5 core 0.25 mm2 type with outer screen for data
• 5 core 0.5 mm2 type with outer screen for power

However, another suitable EMC protected and environmentally correct cable would suffice.

Q:   I only have a battery power supply - what are the constraints on this DC power supply e.g. regulated, fully rectified ¾ A for use with a 24 VDC instrument?

A:    As the tolerance is from 22 to 30 VDC we would suggest a 24 VDC supply with tolerance of 10 percent only. The supply is best fully rectified and the Thies max current draw is specified at 24 VDC with 750 mA but would suggest to err on the side of caution and look for something with a bit more...for example 900 mA or 1 A in case there is a surge when the heating does kick in and brings current draw up to max.

Q:   Is a data record written for each recorded drop?

A:    Yes in drop interrupt mode. Other modes of operation provide different information in 1 minute intervals.

Q:   I need to measure precipitation (although droplet size/shape distribution would be very nice data to have in future) and the most important criteria is to:

• provide measurements of precipitation in mm/h
• average over periods of 1 minute
• to poll and collect the data via SNMP over an IP network

Is the LPM the best instrument to do this with?

A:    Both the LPM or the MRR (Micro Rain Radar) would fit the bill, however, the LPM is more cost effective if an in-situ point measurement would suffice. If you need this information over a vertical profile in the atmosphere, for example to obtain freezing level height and track movement then the MRR is best.

a) provide measurements of precipitation in mm/h ...
Both devices provide an accumulation amount of precipitation in mm/hr. The LPM can also be ordered with optional digital outputs that can act as a start/stop of precipitation device (relay) to switch external equipment or windows, etc.. as well as to work as a line level pulse output similar to a tipping bucket rain gauge feature (in addition to the standard output with drop size distributions along with present weather codes in the form of SYNOP, METAR, NWS code). 

b) average over periods of 1 minute ...
Both devices do indeed provide averaged output of drop size distributions of 1 minute (although the MRR provides 10 second raw and averaged data which also allows the user to post process the data if, at a later date one noticed a setting that was out of adjustment or wished to change settings post measurement to see the variances).

The LPM can be set up to work in standard mode which provides the minute averaged data and drop size distributions OR can be set to a mode called 'event mode' which then produces a unique data string for each and every single particle event that passes through the device (although this does not produce a drop size distribution and is instantaneous and not averaged.)

c) to poll and collect the data via SNMP over an IP network ...
The MRR has a module that converts the RS232 signal to Ethernet and therefore would be ideal for what you have suggested. The LPM does not and the output is strictly RS485 (or RS422/RS232 if you use a converter). You could use a serial RS232 to Ethernet converter to get the signal into the format you have suggested (googling for such devices should bring up several options). Alternatively, you could use the optional LPMView software to run the server software of the device and from any remote client location then connect and view the data.

Thank you for visiting www.biral.com/met/precipitation/lpmfaq.htm