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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#1
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Between 17:30 and 20:30 this evening we had around 40mm of rain according to
my automatic (LaCrosse WS-3600) weather station. According to my manual cone-shaped gauge, which is fairly close by, we had around 18mm. The automatic gauge is around 1 metre above ground level, and the manual gauge is stuck into the soil. The automatic seems to correspond well with the manual in normal conditions. So, what's wrong? Maybe I need to replace my gauge ... again! Also TS around 19:00. Graph of today's rain (if you read this today!) from the automatic at http://users.aber.ac.uk/ais/weather/...hp?data=rtoday Adrian -- Adrian Shaw ais@ Adran Cyfrifiadureg, Prifysgol Cymru, aber. Aberystwyth, Ceredigion, Cymru ac. http://users.aber.ac.uk/ais/weather/ uk |
#2
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"Adrian D. Shaw" wrote in message
... Between 17:30 and 20:30 this evening we had around 40mm of rain according to my automatic (LaCrosse WS-3600) weather station. According to my manual cone-shaped gauge, which is fairly close by, we had around 18mm. The automatic gauge is around 1 metre above ground level, and the manual gauge is stuck into the soil. The automatic seems to correspond well with the manual in normal conditions. .... If you have had readings that have corresponded well in the past (over a long period), then I would suspect a 'one-off' problem with one or other of the gauges: the declared rainfall from the LaCrosse sounds high to me - the showers etc., yesterday were pretty heavy, but I'm not sure we had anything quite that perky. Try doing a test with the auto by putting a measured amount of rainfall through it. As you had a thunderstorm, would there be any lightning interference with the system? Even with high-end professional kit, things can go wrong (witness Heathrow/03772 last couple of days), so don't necessarily go out and replace the gauge / electronics etc., just yet: might have been a one-off 'glitch'. Martin. -- FAQ & Glossary for uk.sci.weather at:- http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm and http://booty.org.uk/booty.weather/metindex.htm |
#3
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![]() Martin Rowley wrote: Even with high-end professional kit, things can go wrong ... 'Bucket-bounce' even on the best TBRs can be a problem, particularly in high rainfall rates: the bucket is filling and tipping so quickly, it can 'bounce' part-way past the reed switch, counting two tips. Some loggers can be set to refuse two pulses within (say) 500 msec - which at 0.2 mm tip equates to 1440 mm/hr, which is well above the design threshold of the instrument itself - which solves the problem. I have two TBRs and for a while I found one was showing anomalously high rates during close thunderstorms (one agreed with the checkgauge, the other didn't - you always need a three-way split to be sure which is correct) - presumably due to induced currents in the (long) cable run. Screening the cable run solved this problem. If yours is wireless, then obviously this won't be directly relevant, but you may find close 'sferics' induce a pulse as Martin suggests. HTH. Stephen Burt Stratfield Mortimer, Berkshire |
#4
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Thanks Martin and Stephen for your advice, I'll wait a bit before I decide
to replace the gauge. I don't think the thunderstorm was quite close enough to have had an effect on the cables, and anyway it happened again later in the evening when no TS was around. Adrian -- Adrian Shaw ais@ Adran Cyfrifiadureg, Prifysgol Cymru, aber. Aberystwyth, Ceredigion, Cymru ac. http://users.aber.ac.uk/ais/weather/ uk |
#5
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On 29 Aug 2006 21:43:02 +0100, Adrian D. Shaw wrote:
I don't think the thunderstorm was quite close enough to have had an effect on the cables, and anyway it happened again later in the evening when no TS was around. My money would be on electromagnetic interference of some sort, be it from lighting or the chap down the road doing a spot of welding... The LaCrosse is budget kit like my Oregon. That was very prone to picking up interference on the rain gauge until I fitted a capacitor and resistor at the head end. This stops the "bucket bounce" problem either from rapid tipping or very slow tipping. It also improved the immunity to interference, thunderstorms within 20 miles would drive it potty, switch some things on/off in the house would also be registered. I can't remember the series and/or parrallel capacitor/resistor wiring I used. -- Cheers Dave. pam is missing e-mail |
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