I've discovered that the problems we've been experiencing on our Instromet
weather station with regards to spikes in rainfall and windspeed data is due
to RF interference. The source of this is going to be difficult to track
down, but one solution I've read is to fit a ferrite? to the serial cable
connected to the PC.

Does anyone else have experience of this sort of interference and, if so,
what solutions have you found?

Mike

Pitsford Hall
www.northantsweather.org.uk

Mike Lewis wrote:
I've discovered that the problems we've been experiencing on our Instromet
weather station with regards to spikes in rainfall and windspeed data is due
to RF interference. The source of this is going to be difficult to track
down, but one solution I've read is to fit a ferrite? to the serial cable
connected to the PC.

Does anyone else have experience of this sort of interference and, if so,
what solutions have you found?

Mike

Pitsford Hall
www.northantsweather.org.uk



Mike

RF interference is well known to radio hams.

Despite having held a licence for 30 years, it's a long time since I
fired up a rig!!!

ISTR that 2 or 3 turns through a "donut" ferrite coil was the starting
point to curing RFI, although that may impact on the wanted signals if
the baud rate is high enough.

Very much a "suck it and see" game with RFI I'm afraid.

Good luck

Regards

Neil

I've found that there are some clip-on ferrite cores that you can buy,
whereby the cable runs inside rather than as a coil outside. Do you think
these are worth trying - say attaching one to the wind sensor cable and one
to the rain cable. They're around £1-2 each.

Mike

"Neil" wrote in message
...
Mike Lewis wrote:
I've discovered that the problems we've been experiencing on our
Instromet weather station with regards to spikes in rainfall and
windspeed data is due to RF interference. The source of this is going to
be difficult to track down, but one solution I've read is to fit a
ferrite? to the serial cable connected to the PC.

Does anyone else have experience of this sort of interference and, if so,
what solutions have you found?

Mike

Pitsford Hall
www.northantsweather.org.uk



Mike

RF interference is well known to radio hams.

Despite having held a licence for 30 years, it's a long time since I fired
up a rig!!!

ISTR that 2 or 3 turns through a "donut" ferrite coil was the starting
point to curing RFI, although that may impact on the wanted signals if the
baud rate is high enough.

Very much a "suck it and see" game with RFI I'm afraid.

Good luck

Regards

Neil

On Fri, 28 Mar 2008 19:58:59 -0000, Mike Lewis wrote:

I've discovered that the problems we've been experiencing on our
Instromet weather station with regards to spikes in rainfall and
windspeed data is due to RF interference.

How are the sensors connected back to the consol, wires or radio?

to the serial cable connected to the PC.

It might be getting into the serial cable but bear in mind that RS232 runs
at a nominal +/- 12V signal level but should work down to +/- 3V.

--
Cheers
Dave.

Dave Liquorice wrote:
On Fri, 28 Mar 2008 19:58:59 -0000, Mike Lewis wrote:

I've discovered that the problems we've been experiencing on our
Instromet weather station with regards to spikes in rainfall and
windspeed data is due to RF interference.

How are the sensors connected back to the consol, wires or radio?

to the serial cable connected to the PC.

It might be getting into the serial cable but bear in mind that RS232 runs
at a nominal +/- 12V signal level but should work down to +/- 3V.


I assume you use a mains extension cable that is supressed, standard £10
job, the reason I mention this is I used to get -50°C spikes on my WMII
everytime the tumble drier was switched on, but one of these
cables/sockets sorted the problem out.

--
Keith (Southend)
http://www.southendweather.net
e-mail: kreh at southendweather dot net

On Fri, 28 Mar 2008 19:58:59 -0000, "Mike Lewis"
wrote:

I've discovered that the problems we've been experiencing on our Instromet
weather station with regards to spikes in rainfall and windspeed data is due
to RF interference. The source of this is going to be difficult to track
down, but one solution I've read is to fit a ferrite? to the serial cable
connected to the PC.
You have not described the unit wiring/cabling setup. Is it a single remote unit
with a single RS232 cable back to the PC? Or is there more wiring involved? How
is/are the remote unit(s) powered?. Is the signal cable screened? Length of
cable? Ground level or elevated?
Basically does it /look/ like an aerial?
RF signal are usually present for enough time to pass a message of some sort
(speech/data) and a local transmitter could result in your aerial picking up
enough to upset the sensors (probably not the PC). If you have virtually
continuous recording data and only get narrow spikes then I would be more
inclined to suspect the power source.

Geo

If you are not familiar with Instromet is rather difficult to describe the
wiring set up, but here goes:

The system runs from a inside junction box which receives signals via
cabling from the various external sensors - around 5. The output from the
junction box goes to both a large analogue display panel and separately to a
PC routed via a datalogger. The link to the PC uses an RS232 cable. However,
the system is linked to a second PC (used as a back-up) via a data transfer
switch - this splits the signal from the datalogger. All the sensors are
elevated some 8m off the ground and the wind and sunshine sensors an
additional 5m approx. on top of a mast. So I guess yes...it is acting rather
like an aerial.

However, the spikes are narrow - perhaps just one or two a day. I am
therefore assuming the problem lies with EMI. I've attached a number of
ferrite cores on the various cables as well as the serial leads and now just
have to wait and see if this solves the problem.

Mike

"Geo" wrote in message
...
On Fri, 28 Mar 2008 19:58:59 -0000, "Mike Lewis"
wrote:

I've discovered that the problems we've been experiencing on our Instromet
weather station with regards to spikes in rainfall and windspeed data is
due
to RF interference. The source of this is going to be difficult to track
down, but one solution I've read is to fit a ferrite? to the serial cable
connected to the PC.
You have not described the unit wiring/cabling setup. Is it a single
remote unit
with a single RS232 cable back to the PC? Or is there more wiring
involved? How
is/are the remote unit(s) powered?. Is the signal cable screened? Length
of
cable? Ground level or elevated?
Basically does it /look/ like an aerial?
RF signal are usually present for enough time to pass a message of some
sort
(speech/data) and a local transmitter could result in your aerial picking
up
enough to upset the sensors (probably not the PC). If you have virtually
continuous recording data and only get narrow spikes then I would be more
inclined to suspect the power source.

Geo

On Sat, 29 Mar 2008 13:26:00 -0000, "Mike Lewis"
wrote:


However, the spikes are narrow - perhaps just one or two a day. I am
therefore assuming the problem lies with EMI. I've attached a number of
ferrite cores on the various cables as well as the serial leads and now just
have to wait and see if this solves the problem.

OK - I had a quick look at their site and see that the basic sytem is supplied
with 25 metre screened cabled from the analogue sensors. Also noted that a 12v
90mA supply would power the kit. If you have a charged battery available it
might be worth running the system for a day with no mains connected to eliminate
a power feed problem.
Is there any time pattern to the spikes (lighting up time for instance)?
I suppose you could miss some if you are only sampling every 5 minutes...

Geo

"Geo" wrote in message
...
On Sat, 29 Mar 2008 13:26:00 -0000, "Mike Lewis"
wrote:


However, the spikes are narrow - perhaps just one or two a day. I am
therefore assuming the problem lies with EMI. I've attached a number of
ferrite cores on the various cables as well as the serial leads and now
just
have to wait and see if this solves the problem.

OK - I had a quick look at their site and see that the basic sytem is
supplied
with 25 metre screened cabled from the analogue sensors. Also noted that a
12v
90mA supply would power the kit. If you have a charged battery available
it
might be worth running the system for a day with no mains connected to
eliminate
a power feed problem.
Is there any time pattern to the spikes (lighting up time for instance)?
I suppose you could miss some if you are only sampling every 5 minutes...

Geo

Thanks. The timing of the spikes varies but is generally at some point
through the afternoon. However, rainfall tends to spike overnight - but only
when it has been raining! I'm hopeful that the ferrite and increased
sensitivity of the UPS should do the trick, so I'll wait and see.

Mike