[hvalentim]

A piece of info some may find useful.

I had success running a SHT15 temp/hum sensor using a 20 (twenty) meters long cable (4 x 0,22mm2).

Sensor used:
Digital Temperature & Humidity sensor SHT15 AVR ARM For - Arduino Compatible


Cable used (CNC4):
http://www.pai.pt/ms/download/media/19/4...46ae9d.pdf

I am not saying this should be taken for granted under all circumstances. I am just saying it worked for me during the half an hour or so I had it running. Also, this cable is not insulated and is prone to degradation by exposure to sunlight.

Furthermore, the all point of a wireless system is skipping the need for extending long cables...

In practice I am not planning to use more than 2-3 meters. Still, the "5 meters maximum length" is perhaps on the conservative side. Which I reckon is always a good starting point.

[werk_ag]

I had success running a SHT15 temp/hum sensor using a 20 (twenty) meters long cable (4 x 0,22mm2).

That's another interesting test.

In practice I am not planning to use more that 2-3 meters. Still, the "5 meters maximum length" is perhaps on the conservative side. Which I reckon is always a good starting point.

Indeed, the SHT1X (when powered by 5V) and the DHT22 can be used with very long cables. And you are right, most of the time I give very conservative specs, this way I'm sure things will work in any circumstances.

[hvalentim]

While studying the limits of stuff so as to define optimal placement I have also found much to my surprise that if you add 15 meters of phone cord extension to the original ~2,5 mt. supplied cable of FineOffset anemometer+wind-vane it works like a charm.

[werk_ag]

Have you compared the readings with the 2.5m cable, and the readings with the 2,5m + 15m cable?

You will always get readings, even with a 100m or 200m cable, but they could not be reliable. In fact with just 30m they aren't, I don't know if with 17.5 meters, they are.

[AllyCat]

Hi,

Hmm, that picture (in #1) doesn't look much like a "genuine" calibrated Sensiron humidity sensor, but I guess it's a lot cheaper.

if you add 15 meters of phone cord extension to the original ~2,5 mt. supplied cable of FineOffset anemometer+wind-vane it works like a charm.

The FO anemometer uses only a "mechanical" magnetic reed switch and the vane resistance varies from 660 ohms up to 120 kohms, so a few tens of ohms (of the cable) is unlikely to affect the measurements, provided that a suitable low-pass filter is included (perhaps just a capacitor across the input) to remove any "garbage".

However, issues are more likely to be encountered with the original Fine Offset transmitter, because it uses a rather weak pullup current (~20 uA) for the anemometer. Also, the ADC "ramp" (for the vane) is applied directly to the cable, so radio interference and capacitive cross-coupled "spikes" can cause malfunctions with extended cables.

Cheers, Alan.

[hvalentim]

Hmm, that picture (in #1) doesn't look much like a "genuine" calibrated Sensiron humidity sensor, but I guess it's a lot cheaper.

It seems to have a genuine sensor, not sure about the calibration tough.

Still I also own a definitely genuine SHT75 which actually has more accurate spec.s. I am reserving it to my second two meters from the ground "as temp. should be measured" unit.

The problem with the SHT75 is the 1,27 mm pitch which makes it difficult to find a suitable connector.

The FO anemometer uses only a "mechanical" magnetic reed switch and the vane resistance varies from 660 ohms up to 120 kohms, so a few tens of ohms (of the cable) is unlikely to affect the measurements, provided that a suitable low-pass filter is included (perhaps just a capacitor across the input) to remove any "garbage".

Thanks for the tip. I ended up using just a 3 meters extension. Did some tweaking on the variable resistor and it seems to be working.