On Monday, April 23, 2018 at 7:25:32 PM UTC+1, Nick Gardner wrote:
On 22/04/2018 20:28, Graham Easterling wrote:
OK, there are a few assumptions, but all this suggests that the BLake Larsen is under-recording slightly (compared to Camborne) by perhaps 5%, but certainly a fair bit less than the 15% that Nick is experiencing.

Graham, Ole has just contacted me and has recalibrated the threshold as
it was set too high. That probably explains the rather large
discrepancy. Also, I have noted that the sensor is catching a shadow
caused by the apex of the dormer before sunset. The sensor is a little
below the R&D recorder which itself gets a clear view of the western
horizon. My mistake so I'll plan to get 'up there' and sort it at some
point in the near future.

Interesting that today the BL recorded 1.2 hours and the R&D recorded
1.1 hours. That's the first time the BL has recorded more so the
calibration seems to have worked!

--
Nick Gardner
Otter Valley, Devon
20 m amsl
http://www.ottervalleyweather.me.uk

Glad you've found the probable issues Nick. I've obviously had no experience of using the Blake Larsen, but everything I'd read, and been told, suggested that over a month or 2 there was very little difference between it and the other recorders. Alan had also told me about successful parallel trials.. I thought there had to be a reason(s) why yours was 15% low.

I know that a firm has now taken over development of the Sun Recorder, so hopefully there will be some progress on the data logging front.

Graham
Penzance