Cumulus Support

Hi Chaps I am wanting to move bits of my fine offset WH1090 around my garden for better results but I am unsure if the cable that I am looking at on ebay is the correct one. I want to move the anemometer and wind vane about 25m away from the temp/transmitter and rain gauge. Please could someone tell me if this http://www.ebay.co.uk/itm/370711964262? ... 1423.l2649 is the correct cable needed for the job.
Thanks
Grahame

what you need to check is that the cable is not crossed as in it is straight pin 1 to pin 1 not pin 1 to pin 4. the wind direction uses the out side to contacts and anemometer the 2 inside (I think) may be the other way round. the cable your looking at should be ok but don't quote me on that but most adsl cables are straight.

I'm thinking... if we can create some local sources for extension cables (people who have access to an RJ11 crimp tool), we could supply them to people in our region, so a fairly exact length needed.

I know that, for network purposes, the max length of cat5/cat6 UTP (a good qiality network cable) is 100 metres. Does anyone have any idea what the maximum cable length is that, for instance, Fine Offset tolerates?

Also, there is of course the UV degradation issue. How does Cat5 or Cat6 stand up to UV degradation?

[edit: Foot-in-mouth moment. I could've googled this myself. As a matter of fact, I just did:
https://www.google.nl/#hl=nl&gs_rn=1&gs ... 80&bih=925 ]

The eBay item mentioned above may not be outdoor quality...

I will have a look at the cable being used at the mo once the snow clears and I can use my ladder. The new cable from ebay will be run through trunking so it should be well protected from the elements.

Thanks Grahame

Any extension cable for the wind instruments should incorporate twisted pairs, to reduce the occurrence of spikes in temperature that FO units are subject to (much has previously been written on this topic)
Cat5 or Cat6 cable in recommended, rather than flat phone cable fitted with RJ11 connectors. I'm using a 10m extension and found line sockets for the RJ45 plugs will also accept RJ11 plugs that connect to the FO units.
I don't think the issue of crossover cable or not applies, as they are only terminating with reed switches in the instruments, which are polarity insensitive.

Ned wrote:I don't think the issue of crossover cable or not applies, as they are only terminating with reed switches in the instruments, which are polarity insensitive.

Hi,

The middle two pins on the connector carry the wind speed pulses and the outer pair (of the four) carry a resistance value which varies with the wind direction. So one "twisted pair" (if used) must be connected to the inner contacts and a second to the outer pair. Similarly, if a "crossed" cable is used (I don't think they're very common in RJ11/12 format cables) then it's important to ensure that only the two inner connections and the two outer connections become (individually) reversed.

However, when extending the wind cable (on most FO models), there is indeed a very serious risk that you will upset the external temperature measurements (with spikes or worse). The reason is that the Wind Vane signal (a variable resistance value) is permanently connected to the input of the same Analogue-Digital conveter as is used by the (thermistor) temperature sensor (but the 308x models work differently). The A-D converter is very sensitive so even a slight injection of voltage (or worse, a tiny leakage current between the cores due to moisture in the connectors) can cause serious external temperature issues (and perhaps faulty wind direction reports as well).

Cheers, Alan.

Bumping an ancient thread I know. But it's directly relevant.

I extended the cable for the wind sensors on my WH1081 (actually Maplin N96GY). I did so with this 15m Twisted Pair fully wired RJ11 cable and this RJ11 Coupler. I wrapped the whole thing up extensively with self-amalgamaging tape and sealed where the tape met the cable at each end with silicone. I then cable tied it into a loop to take the strain - i.e. the cable from the WH1081 was cable tied to the RJ11 extension such that the connectors were not under the strain of the weight of the cable etc.

All worked fine when it was on the ground. Wind direction and speed sensors were working fine. Then I got the aerial installer to put it on the roof. He mounted the wind sensors, taped up the cable, and taped the joiner to the mast.

You can guess what I'm going to say now: it doesn't work. The wind direction sensor works, but it says the wind speed is 0 no matter what.

I can't exactly shimmy up there and do anything, I'm a wheelchair user in a care home. I guess I am stuffed?

Any suggestions as to how to troubleshoot and identify where the fault is would be great. Can the wind speed sensors be tested with a multimeter, for example? Which pair, and how?

Thank you

Hi,

Yes, the anemometer circuit is very straightforward. A magnetic reed switch is connected across the two middle contacts of the RJ11 plug so you should see pulses of low resistance (a few ohms, but not critical) from "infinity" (typically needs to be > 50 kohms), twice for each revolution. Sometimes the RJ11 plugs make poor contact in the transmitter socket, or perhaps you have some wires "crossed" in the RJ45 extension.

Normally the problems are with the wind direction sensor; the range of resistances is high (< 1 k to >100 k) and any "leakage" between the cores can also cause major errors in the external temperature readings. The vane resistance is connected across the two outer contacts (of 4) in the RJ11 plug. Each sensor's pair of wires can normally be reversed without issue.

Cheers, Alan.

Thanks Alan, that was very useful information. So effectively, the anenometer short circuits the two inner contacts every time it goes round 180º. Got it.

It worked through the extension wire before I got the aerial installer to put it up there. I can only assume that there was some intermittent contact somewhere that has now broken on manipulation of the cable (or, more likely, a connector.) Not much that can be done I guess, if it's above ground level, without getting somebody out. But I will fidlle with the ground-level end just in case. (on a gentle wind day so I can see the changes in resistance on my multimeter.)

Thanks

Doug