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Lost Sensor Contact!!

Discussion specific to Fine Offset and similar rebadged weather stations
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

Re-connected wind sensors at 0940 (16 Apr 2010) and almost immediately got a spike! I'll leave it a few hours and see if there's another.
24hrs-Temperature-only8.png
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
EvilV
Posts: 127
Joined: Wed 27 Jan 2010 11:28 am
Weather Station: Watson W-8261
Operating System: XP
Location: NE7 7QE Newcastle upon Tyne UK

Re: Lost Sensor Contact!!

Post by EvilV »

Could the socket be a bit dodgy?

You could try connecting a spare bit of phone lead with an rj11 plug on it and see if the lead is picking up interference. In the somewhat unlikely case that it is that, you can probably solve it by winding the lead around a ferrite ring near the transmitter socket. If you have a ferrite ring handy you could do that right away. If you have a long lead like I do with the wind apparatus up in the air and the temp sensors and transmitter down below, you have a pretty good hf antenna going up the pole and possibly conducting unexpected voltages into the kit.

If it isn't that, maybe there is some fault in the anemometer or in the wind vane.

You are definitely getting close to the cause now.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

No more spikes as yet - just ups and down as the sun comes out and goes in. My home made screen has reduced the effect of solar radiation from 2-3 degrees to less than 1 but it needs the aspirating fan (currently not connected) to reduce it further. It seems that interference is being picked up by the cables so I'm going to get some clip-on ferrite beads.
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

EvilV wrote:Could the socket be a bit dodgy?

You could try connecting a spare bit of phone lead with an rj11 plug on it and see if the lead is picking up interference. In the somewhat unlikely case that it is that, you can probably solve it by winding the lead around a ferrite ring near the transmitter socket. If you have a ferrite ring handy you could do that right away. If you have a long lead like I do with the wind apparatus up in the air and the temp sensors and transmitter down below, you have a pretty good hf antenna going up the pole and possibly conducting unexpected voltages into the kit.

If it isn't that, maybe there is some fault in the anemometer or in the wind vane.

You are definitely getting close to the cause now.
I agree that the pole and cable is a pretty good hf receiving aerial and I do think that's likely to be the problem. The pole is 6.3m (about 20ft) high and the cable is taped to it in several places but leaves it about 4 or 5ft above ground to go across to the tx unit. This would tap off anything received by the pole. The fact of the pole being grounded at the bottom end would not really help, depending on the wavelength of the interference.

I've checked the RJ11 plug at the tx unit and it seems OK but I've tied the cable so that it can't move in the wind.

There is one major source of interference but that is transmitting all the time AFAIK. We are about a mile or so from the Stockland Hill TV and DAB radio transmitter, on the next hill. I think this transmits 200KW at UHF.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

Haven't got any ferrite rings but have found a ferrite aerial (LW/MW radio) and I've wrapped the cable several times round that - don't know it it'll work. I've also re-connected the fan. Time of mods 14:40. Plot of temperature to date attached.
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

Just to confirm when the spikes started, here's a temperature (only) plot over the last fortnight.
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

16:50 disconnected wind sensors cable and connected fan. Wrapping the wind sensor cable several times round a ferrite rod aerial didn't help - got a spike.
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
EvilV
Posts: 127
Joined: Wed 27 Jan 2010 11:28 am
Weather Station: Watson W-8261
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Location: NE7 7QE Newcastle upon Tyne UK

Re: Lost Sensor Contact!!

Post by EvilV »

Gina wrote: There is one major source of interference but that is transmitting all the time AFAIK. We are about a mile or so from the Stockland Hill TV and DAB radio transmitter, on the next hill. I think this transmits 200KW at UHF.
I found something which says that the Stockland Hill transmitter puts out 30KW of Freeview signal. I don't know what else is coming out of there. However, since TV transmissions are pretty much continuous I doubt they would account for occasional spikes like you are getting.

http://www.ukfree.tv/txdetail.php?a=ST222014

I'd favour some erratic electrical source like a big motor switching on or a bad relay in some equipment that sends out wideband radio noise. Do you have any high voltage power lines near? Maybe occasional arcing in a power line insulator could do it.

Maybe to isolate the actual wind instruments, you could disconnect the instruments up at the top of the pole (assuming you're just running a pluggable extension down the pole) but leaving the long wire connected at the bottom. This would allow it to operate as a receiving antenna, if it is doing, and you wouldn't have confusion from the anemometer or the direction indicator.

I'm not sure if a ferrite rod with a few winds would be as effective as a proper ferrite ring. I think the flux is greater in a ring, but I'm not sure about that, and if it is wideband noise at low frequencies, a ferrite ring might not stop it.

There could still be some component failure in the wind instruments.

Personally, I'd leave the fan disconnected for the time being. No sense in having a more complex situation then you have to in a case like this until the problem is finally nailed.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

EvilV wrote:I found something which says that the Stockland Hill transmitter puts out 30KW of Freeview signal. I don't know what else is coming out of there. However, since TV transmissions are pretty much continuous I doubt they would account for occasional spikes like you are getting.

http://www.ukfree.tv/txdetail.php?a=ST222014
Thanks. I was a bit wrong there.
I'd favour some erratic electrical source like a big motor switching on or a bad relay in some equipment that sends out wideband radio noise. Do you have any high voltage power lines near? Maybe occasional arcing in a power line insulator could do it.
Yes, I thought that. The nearest overhead power lines are around 100 yards/metres and 11Kv. The 240v supply is overhead, on poles.
Maybe to isolate the actual wind instruments, you could disconnect the instruments up at the top of the pole (assuming you're just running a pluggable extension down the pole) but leaving the long wire connected at the bottom. This would allow it to operate as a receiving antenna, if it is doing, and you wouldn't have confusion from the anemometer or the direction indicator.
The cable attached to the wind vane unit reaches down to about halfway down the mast (3m) where there is a female/female coupler, then my extension cable goes down the mast and across to the tx unit (about 5ft above ground). I can disconnect at the coupler. I think disconnecting the wind sensors half way up the mast should still be an effective test as the cable is taped closely to the mast and there should be plenty of capacitive coupling from mast to cable.
I'm not sure if a ferrite rod with a few winds would be as effective as a proper ferrite ring. I think the flux is greater in a ring, but I'm not sure about that, and if it is wideband noise at low frequencies, a ferrite ring might not stop it.
No, I didn't think a rod would be as good and it proved of no benefit at all. If a ferrite bead doesn't stop it I'm thinking of putting LC filters in all 4 wires near the tx unit and running the common capacitor connection to earth with a wire down to an earth spike.
Personally, I'd leave the fan disconnected for the time being. No sense in having a more complex situation then you have to in a case like this until the problem is finally nailed.
The fan has been connected and running all night and there have been no spikes. Both wind sensors and rain gauge cables were unplugged from the tx unit. So I think I have eliminated the fan as the source of interference.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

10:30 17 Apr 2010 Connected rain gauge at tx unit
11:50 17 Apr 2010 Connected wind sensors again
13:00 17 Apr 2010 Disconnected wind sensors. Connected another RJ11 cable wound round wind sensor cable and mast.

As soon as I reconnected the wind sensors I got a spike. I haven't got time to lower the mast and re-erect it ATM so have taken another RJ11 cable (from an old modem - 4 wire) and plugged that into the wind socket on the TX unit. Then wrapped it around the wind sensor cable and round the mast for a couple of feet. So wind sensors not connected but some capacitive coupling between the sensor cable to the test cable.
24hrs-Temperature-only-c.png
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

Not seen any spikes since using the separate cable (except maybe a very small one early on).
24hrs-Temperature-only-d.png
Here's photos of the cable arrangement.
cables.JPG
mast.JPG
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

Got a spike now! That seems to confirm that the cable/mast is picking up interference and transferring it to the temperature circuit, which is adjacent to the wind socket. Now it seems a matter of suppression. Either a ferrite bead on the cable or a choke and capacitor on each incoming line.
24hrs-Temperature-only-e.png
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Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

I'm thinking of the following, from Maplin :-
Clip on ferrite beads - http://www.maplin.co.uk/Module.aspx?ModuleNo=32799

Order........Part..........Max.........Max...........Min........Attenuation (Ω)
Code........number.....diameter...length......hole dia.....25 MHz.....100MHz
N95AB.....HEM3018.....20.50.......36............6.5.........120............190
All dimensions are in mm.

RF Chokes - http://www.maplin.co.uk/module.aspx?moduleno=3660
I was thinking of the 1mH one with the idea that the higher the value the better. Probably used with a 0.1uF ceramic capacitor.
RF-suppressor.png
The circuit would connect to the TX unit with a short RJ11 cable and for the earth I was thinking of a wire from the circuit, down the post to an earth spike in the ground.

Does this sound sensible, EvilV? (or anyone else au fait with this subject)
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Last edited by Gina on Sat 17 Apr 2010 9:38 pm, edited 1 time in total.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
geoffw
Posts: 556
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Weather Station: Davis Vantage Vue
Operating System: Windows 10
Location: Pembrokeshire West Wales UK
Contact:

Re: Lost Sensor Contact!!

Post by geoffw »

Gina wrote:I'm thinking of the following, from Maplin :-
Clip on ferrite beads - http://www.maplin.co.uk/Module.aspx?ModuleNo=32799

Order........Part..........Max.........Max...........Min........Attenuation (Ω)
Code........number.....diameter...length......hole dia.....25 MHz.....100MHz
N95AB.....HEM3018.....20.50.......36............6.5.........120............190
All dimensions are in mm.

RF Chokes - http://www.maplin.co.uk/module.aspx?moduleno=3660
I was thinking of the 1Mh one with the idea that the higher the value the better. Probably used with a 0.1uF ceramic capacitor.
RF-suppressor.png
The circuit would connect to the TX unit with a short RJ11 cable and for the earth I was thinking of a wire from the circuit, down the post to an earth spike in the ground.

Does this sound sensible, EvilV? (or anyone else au fait with this subject)
Hey Gina ..... Come over here and rewire my house for me whan you've finished! :mrgreen:
Geoff
Image
Gina
Posts: 1885
Joined: Sat 21 Feb 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Lost Sensor Contact!!

Post by Gina »

geoffw wrote:Hey Gina ..... Come over here and rewire my house for me whan you've finished! :mrgreen:
:lol:

Up to date temperature only plot :-
Image
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.
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