Cumulus Support

So I see Davis have released a new more accurate temperature/humidity sensor based on the new Sensirion SHT31. It is paired with new transmitter board firmware, but it will work with older boards if you use a 0.5 C offset in the console.

Before you DIYers rush out and buy one to play with, Sensirion have announced that there will be an even more accurate SHT35 available "second quarter 2016".

Interesting stuff.

Hi Mark,

I can't find anything about this. Have you got any links you can post please?

Thanks

Hi Adrian, there is a thread on this subject on the WX Forum.

I've just noticed, the new SHT31 sensors are only £2.70 at Farnell!

But the minimum order quantity is 150 !

Ah, yes, good spot. It is £3.82 for 1, still pretty cheap.

http://uk.farnell.com/sensirion/sht31-d ... 4218/false

Sensirion have released the SHT35 spec sheets as well now, not sure when they will be available though.

mcrossley wrote:So I see Davis have released a new more accurate temperature/humidity sensor based on the new Sensirion SHT31. It is paired with new transmitter board firmware, but it will work with older boards if you use a 0.5 C offset in the console.

Definitely a much better sensor than the SHT75. The response of the sensor is fantastic. Today is a "well mixed" day atmospherically speaking, and the sensor is picking up much more detail of the humidity variations you can expect to see in these conditions. I'm well chuffed

Unfortunately the sensor that Davis use is the sht31-LSS legacy protocol sensor which is not readily available. The sensors on Farnell are the SHT31-DI i2c protocol and will not work with the VP2.

Yep, I've tried to source them, no luck so far...

And for those who are considering building your own sensor, this should only be attempted if you are experienced at very small surface mount soldering. The chip measures 3x3 mm and has 8 pads that require connecting. I have over 20 years experience doing this sort of thing and have found this one particularly challenging.

belfryboy wrote:And for those who are considering building your own sensor, this should only be attempted if you are experienced at very small surface mount soldering. The chip measures 3x3 mm and has 8 pads that require connecting. I have over 20 years experience doing this sort of thing and have found this one particularly challenging.

Guess we'll be waiting for you to make them available to us then

Perhaps worth noting that Davis seem to have had a major rethink about pricing on replacement T/H sensors. No idea why, but it's obviously got to be good news for users. The UK SSP on 7346.074, which contains the new SHT31 sensor, is £45 inc VAT. (Admittedly set before the recent devaluation of Sterling, so could be subject to revision).

Couple of further notes, in case anyone is unaware:

1. While the .074 part is plug compatible with post-2005 but pre-AS revision VP2 stations, it does require a 0.5C temperature offset entering in the console. ('AS' being the VP2 revision at which the SHT31 became standard and which uses a slightly updated SIM board design.)

2. There is also 7346.221 part (but we're still awaiting delivery of these), which is as per the .074 part but with the sensor on a 25ft cable and so the sensor could in principle be located some way away from the ISS, eg in a traditional Stevenson screen.

Hi,

belfryboy wrote:And for those who are considering building your own sensor, this should only be attempted if you are experienced at very small surface mount soldering. The chip measures 3x3 mm and has 8 pads that require connecting. I have over 20 years experience doing this sort of thing and have found this one particularly challenging.

Thanks to the Meteocercal forum, this might avoid a lot of grief for us DIY builders. £10 seems quite reasonable, especially as you don't have to wait for a shipment from China, and it's available in both digital (I2C bus) and analogue versions (but I don't know if that's compatible with the "LSS" version required for Davis').

However, I don't know if that "breakout" board (available with or without RA pins) can accommodate the "weather screen" required for more arduous external applications.

Cheers, Alan.

Unfortunately those are not compatible with the legacy LSS protocol.