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Author Topic: Extending Davis Sensors  (Read 838 times)

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Offline N7XSQ

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Extending Davis Sensors
« on: May 24, 2017, 07:51:15 PM »
Extending the Solar/UV sensors was recommended to Bashy recently. I really don't want to chop the connector of a $300 UV sensor to splice in cable. I previously used telephone extensions with a LaCrosse, but the Arizona sun ate them up in nothing flat.

   What are you guys using for the extension (as in cabling)?   
   Does anybody know how far you can extend the Solar/UV sensors?
   Will the Davis 4-conductor 40ft extension work plug and play?

Davis 6830 (Temperature/Humidity Sensor in a passive fars) comes with an attached 25ft cable, so the T/H sensor can be extended at least that far.  Has anybody extended it further?

Thank you for your support;
Steve


Offline niko

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Re: Extending Davis Sensors
« Reply #1 on: May 24, 2017, 08:16:07 PM »
Davis used to publish a spec for the solar accuracy with a cable extension, but it wasn't one that made much sense and they wouldn't/couldn't clarify it. FWIW it was "+-5% of full scale plus 45 W/m2 per 100'"  I think it's safe to say that extending the cable will degrade the accuracy, but in my experience up to 40' isn't a big deal. Beyond that I would be a bit nervous.

Despite the higher price than phone extension cable I would suggest using the Davis cable which reasonably low resistance, does stand up to UV quite well, and you can be sure it will not result in crossed connections.

Offline BWX

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Re: Extending Davis Sensors
« Reply #2 on: May 26, 2017, 06:07:17 AM »
I believe Davis has a coupler too for joining 2 cables, i may be wrong there and it was in fact my supplier that sold from other sources
nope, im right https://www.scaledinstruments.com/product/davis-7876-040-standard-4-conductor-cable-40-ft-12-m/



No issues with 10m extensions on all sensors here

Offline Timmead

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Re: Extending Davis Sensors
« Reply #3 on: July 23, 2017, 10:45:00 PM »
Am I correct in thinking the T/H sensor is special and needs 6-core cable?
(Yes I know extending it is ill-advised, but I've seen plenty here do it)

Davis don't seem to sell those anymore - can't find them anywhere (or the one I found is 12m which is too long for the delicate sensor to handle).
Do you think this would suffice? https://www.amazon.co.uk/d/Telephones-VOIP-Accessories/Pin-RJ11-Telephone-Cable-3m/B0034ULKF2

Offline niko

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Re: Extending Davis Sensors
« Reply #4 on: July 23, 2017, 11:08:00 PM »
The one you link is 3 meters, not 12 meters. Note that it's wired as a crossover cable so you'll need a joiner that accounts for that. As you say a lot of people extend them without a problem so I would go ahead. 

Offline Timmead

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Re: Extending Davis Sensors
« Reply #5 on: July 23, 2017, 11:38:16 PM »
Thanks.
3m is exactly what I need. I was saying the 12m is too long, which could cause issues with interference.

Quote
Note that it's wired as a crossover cable so you'll need a joiner that accounts for that
I see now that it says the pins are reversed...

Is this one ok? https://www.amazon.co.uk/kenable-RJ12-6P6C-Cable-BLACK/dp/B0051FKFXQ/
If not do you think you could point me in the right direction?  (US sites are fine)
Thanks again!

Offline Timmead

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Re: Extending Davis Sensors
« Reply #6 on: July 23, 2017, 11:53:07 PM »
Aha I think I've found it
For reference: https://www.amazon.com/Cmple-Phone-Cable-RJ12-Straight/dp/B00404QWUE/

Thanks for helping me with the straight/reverse distinction

Offline niko

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Re: Extending Davis Sensors
« Reply #7 on: July 24, 2017, 12:37:30 AM »
Aha I think I've found it
For reference: https://www.amazon.com/Cmple-Phone-Cable-RJ12-Straight/dp/B00404QWUE/

Thanks for helping me with the straight/reverse distinction

Careful! I think these cables and joiners will follow the convention for 'phone cables which are crossed over. So if you get a straight cable it may not work with a standard joiner. I would go with

https://www.amazon.co.uk/kenable-Female-Coupler-Adapter-Joining/dp/B0079I7K54/ref=pd_bxgy_107_2?_encoding=UTF8&psc=1&refRID=KWZNPFF3WNM66J1QK5NE

https://www.amazon.co.uk/kenable-RJ12-6P6C-Cable-BLACK/dp/B0051FKFXQ/

And check the continuity when I install it.

Offline Timmead

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Re: Extending Davis Sensors
« Reply #8 on: July 24, 2017, 01:37:01 AM »
Great, thanks niko.
Will try that out.

Offline BWX

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Re: Extending Davis Sensors
« Reply #9 on: July 24, 2017, 04:44:10 AM »
B&Q do a white 6 core, it's perfect and I have no issues at 10m

Offline mcrossley

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Re: Extending Davis Sensors
« Reply #10 on: July 24, 2017, 09:02:26 AM »
Just one note of caution if the cable will be exposed to the sun - UV resistance. If it isn't stated, then my rule of thumb is... Black sheathing is *usually* more UV stable than white/pale colours.
Mark

Offline BWX

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Re: Extending Davis Sensors
« Reply #11 on: July 24, 2017, 09:15:59 AM »


Good point, mine is underground and up the back of the mast so fairly safe in that respect, there is the small amount coming out of the iss I spose I should electrical tape it.


Quote from: mcrossley on Today at 10:02:26<blockquote>Just one note of caution if the cable will be exposed to the sun - UV resistance. If it isn't stated, then my rule of thumb is... Black sheathing is *usually* more UV stable than white/pale colours.
</blockquote>


Offline niko

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Re: Extending Davis Sensors
« Reply #12 on: July 24, 2017, 01:13:57 PM »
Just one note of caution if the cable will be exposed to the sun - UV resistance. If it isn't stated, then my rule of thumb is... Black sheathing is *usually* more UV stable than white/pale colours.

Good point. That's part of why I chose the one I linked but I should have mentioned it...

Offline Timmead

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Re: Extending Davis Sensors
« Reply #13 on: September 05, 2017, 12:34:15 PM »
Thanks for the help everyone.
I installed the new station this weekend and all went smoothly.
The straight-through 6P6C cable worked perfectly