This week I added the Apogee Instruments TS-100 fan aspirated shield to my setup. Readings from the shield are not exactly what I expected. I'm trying to make sense of the initial data I am getting. Should get some fun out of figuring this out.
I am comparing 4 shields.
2x Barani MeteoShield Pro with the same SHT35 sensor probe from the same seller
1x Davis 7714 with a steel SHT35 probe
1x Apogee TS-100 with the same probe casing as the Barani's, but the SHT35 comes from a different seller
What I am seeing is this. During the night the TS-100 reads a bit lower at times than my other sensors in passive shields. Makes sense, I am guessing. I am hoping it's due to the fact that during the night there's hardly any wind and the ventilated sensor reacts better to dropping temperatures while the passive shields retain slightly more warmth due to lack of ventilation.
Below you can see the graph as it's developing today. It's a rainy day, and only after 10AM does the radiation actually exceed 100 W/m2, though it hasn't hit 200 yet. At that point temperatures start to rise, and I note that the Apogee along with the 7714 start rising quicker than the Barani's. 0.2 degrees higher at points now. Yesterday saw a similar pattern, up to 0.5 degrees higher for the Apogee and 7714 at times. And that under mostly moderate radiation.
Now I am concerned about the Apogee. What could explain the apparent deviation? I am thinking a few things:
- Could it be the fact that the Apogee is open at the bottom and the sensor casing (see below) is warmed slightly by reflected radiation?
- Could it be that the fan sucks air from below that it actually receives air from closer to the ground and therefore a bit warmer?
- Could it be that the sensors reacts differently somehow?
- Could it be that the Barani's are not as responsive is some way?
Other theories?
I've recently come to assume that the Barani's give me very good readings under average conditions, because the results match up very good on average with a nearby station of our Met Office.
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The TS-100 from below.
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