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Old 29-11-2020, 20:18   #1
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What Makes a Good Barometer?

I've seen all kinds of units of measurement and all different prices. I just want something accurate to predict weather.


First off, we use kilopascals here in Canada so it's what I'm used to but what about other countries? What do they use in Latin America How about SE Asia and Europe?

Is there any reason I shouldn't buy used? A thousand dollars for a new (good) one isn't the end of the world but my boat needs everything so it all adds up fast. Prefer to save where possible.
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Old 29-11-2020, 20:21   #2
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Re: What Makes a Good Barometer?

Nearly all cell phones have barometers. They are, as a rule, quite accurate.
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Old 29-11-2020, 22:28   #3
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Re: What Makes a Good Barometer?

Quote:
Originally Posted by Heathenly Twins View Post
I've seen all kinds of units of measurement and all different prices. I just want something accurate to predict weather.


First off, we use kilopascals here in Canada so it's what I'm used to but what about other countries? What do they use in Latin America How about SE Asia and Europe?

Is there any reason I shouldn't buy used? A thousand dollars for a new (good) one isn't the end of the world but my boat needs everything so it all adds up fast. Prefer to save where possible.

Opencpn has a good barometer trend on it with a HAT

Most phones and tablets have a baro, plenty of apps

For a ships set, get a nice set of chelsea, when it comes to all things quality, buying used is not only fine, but also smart. These barometers also have a setting screw, read up on that if you get a set

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Old 29-11-2020, 23:45   #4
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Re: What Makes a Good Barometer?

If what you want is good data, forget the shiny brass aneroid things seen adorning so many yacht's bulkheads. For far less money there are many electronic baros available, and they are in general far more accurate than the standard brass issue.

Not romantic, not scenic, but do not require polishing or tapping, and many include at least primitive barograph functions (and that is quite useful). And the one that has graced our boats for the past 20 years cost the majestic sum of 70 USD. I keep a little log on a sticker on its back, and I've had to change the 4xAAA batteries five whole times in that period. Better than Brasso!

Oh... there is a shiny brass job along with an inaccurate "chronometer" on our bulkhead as well, courtesy of the PO! I never even look at it!

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Old 29-11-2020, 23:57   #5
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Re: What Makes a Good Barometer?

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Originally Posted by Jim Cate View Post
If what you want is good data, forget the shiny brass aneroid things seen adorning so many yacht's bulkheads. For far less money there are many electronic baros available, and they are in general far more accurate than the standard brass issue.

Not romantic, not scenic, but do not require polishing or tapping, and many include at least primitive barograph functions (and that is quite useful). And the one that has graced our boats for the past 20 years cost the majestic sum of 70 USD. I keep a little log on a sticker on its back, and I've had to change the 4xAAA batteries five whole times in that period. Better than Brasso!

Oh... there is a shiny brass job along with an inaccurate "chronometer" on our bulkhead as well, courtesy of the PO! I never even look at it!

Jim
Accuracy wise you see a actionable difference between the digital and the analog?

The iPhone barometer, the HAT2 barometer, and my brass analog all show the same readings, just a different way of displaying the same thing, If you have to tap it, it needs service ,or to be removed, or marked inop
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Old 30-11-2020, 00:34   #6
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Re: What Makes a Good Barometer?

There are numerous weather stations that also give history, temp (inside and out) and humidity. For a honest dedicated fixed unit NASA Marine Meteoman is a good choice.
https://www.nasamarine.com/product/meteoman/
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Old 30-11-2020, 00:37   #7
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Re: What Makes a Good Barometer?

Quote:
Accuracy wise you see a actionable difference between the digital and the analog?
Yep, that I do!

Android instruments of the sort sold to yachtsmen (rather than scientists) can be adjusted to be accurate at specific pressures. However, these instruments are not very linear in their responses, and as one deviates from the pressure at which it was set, the errors increase.

The electronic ones do not suffer from this non-linearity IME. I've checked ours against a nearby BOM site repeatedly and found good agreement, whilst our aneroid varies wildly at pressures that are not in the 1015 mb region (where it ws set).

The folks at Starpath had a lengthy dissertation on this issue in one of their tutorials on wx instrumentation. I've lost track of it, but likely out there somewhere. It was their warnings that alerted me to this issue years ago.

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Old 30-11-2020, 00:54   #8
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Re: What Makes a Good Barometer?

Absolute accuracy in a marine barometer is not a neccesity as what you are really interested in is the trend.

You can find this in the bar graph of historical pressure that many sub $100 small weather stations give you ... or at least they used to ... these days that bar graph seems to have given way to assorted bells and whistles that you will never need.

I have three... one is an Oregon Scientific knock off... the other was bought off ebay as an altimeter... can't find it on Ebay anymore....and the other is from Heinz of this parish...

Even the best aneroid barometers need a tap before reading... its down to the friction in the linkages not being overcome by small pressure changes.... but if you have an aneroid baro you should be noting the pressure in the log at least every four hours if in temperate climes , every two hours in the tropics, and hourly if you suspect a cyclonic weather is in the offing....

This is all a bit of a pain while a digital bar graph is muy facil....
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Old 30-11-2020, 00:55   #9
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Re: What Makes a Good Barometer?

Quote:
Originally Posted by Jim Cate View Post
Yep, that I do!

Android instruments of the sort sold to yachtsmen (rather than scientists) can be adjusted to be accurate at specific pressures. However, these instruments are not very linear in their responses, and as one deviates from the pressure at which it was set, the errors increase.

The electronic ones do not suffer from this non-linearity IME. I've checked ours against a nearby BOM site repeatedly and found good agreement, whilst our aneroid varies wildly at pressures that are not in the 1015 mb region (where it ws set).

The folks at Starpath had a lengthy dissertation on this issue in one of their tutorials on wx instrumentation. I've lost track of it, but likely out there somewhere. It was their warnings that alerted me to this issue years ago.

Jim
But isn’t everyone here using it for marine use, not for scientific lab use? I mean how much accuracy do we really care about?
Not like we are using it as a altimeter to judge wave height

When I got my brass set (baro and chrono that is) for the boat, I set it via the flathead set screw to a nearby airports altimeter setting, its held true alongside the HAT and my iPad/iPhones


This is quite handy, uses the built in baro sensor in many apple devices
https://apps.apple.com/us/app/barome...ro/id923043780
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Old 30-11-2020, 00:58   #10
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Re: What Makes a Good Barometer?

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Originally Posted by El Pinguino View Post
I have three... one is an Oregon Scientific knock off... the other was bought off ebay as an altimeter... can't find it on Ebay anymore.......
Found it...
https://www.ebay.com.au/itm/Waterpro...Cclp%3A2334524
You can see the bar graph in the right hand pair of the four pics..
Its just velcroed to a bulkhead.
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Old 30-11-2020, 10:28   #11
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Re: What Makes a Good Barometer?

Same here, the PO has installed an old style baro which works fine, too, only I want to see the history of at least the last 24h, better 72h.

The most common and highly recommended sensor in electronic devices for recreational use is the Bosch BME290, which also gives temperature and rel humidity. I prefer hPa but if kPa is your thing:

Click image for larger version

Name:	<a title=Screen Shot 2020-11-30 at 6.14.13 pm.jpg Views: 31 Size: 336.8 KB ID: 227918" style="margin: 2px" />


One fellow sailor even had a mechanical baro with paper rolls on board for many years. The ones used in museums, one roll per week, IIRC. He wrote an excellent book about particular events (read: bad weather) that he correlated with the baro pressure leading up to it.

The name of the book escapes me right now though...
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Old 30-11-2020, 11:20   #12
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Re: What Makes a Good Barometer?

ON THAT WIORKS....yes I know, stupid answer but the truth..You dont need bathoscope with smoked paper used in submaines. You just need one that is sized for your eyesight...small ok, meidum size good...large-big expensive.


de W7KFI
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Old 30-11-2020, 11:26   #13
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Re: What Makes a Good Barometer?

Remember the barometer not only tellls you about air pressure and approaching weather, but you can navigate with it...GRIP files (got off of the internet) show bands of different Baro pressure indications....if you match the baro and the map trace you approx where you are,,,,,kinda like navigating by checking depth against map depth lines. de W7KFI
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Old 30-11-2020, 11:59   #14
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Re: What Makes a Good Barometer?

I carry a handheld called "Windmate" from WeatherHawk.
https://www.weatherhawk.com/

This little gadget give all the info a sailor could possibly want...
Barometric pressure
Wind Speed
Temperature
Humidity
Dewpoint
and many more...

I do not go sailing without it...
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Old 30-11-2020, 12:19   #15
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Re: What Makes a Good Barometer?

Quote:
Originally Posted by Heathenly Twins View Post
I've seen all kinds of units of measurement and all different prices. I just want something accurate to predict weather.

First off, we use kilopascals here in Canada so it's what I'm used to but what about other countries? What do they use in Latin America How about SE Asia and Europe?

Is there any reason I shouldn't buy used? A thousand dollars for a new (good) one isn't the end of the world but my boat needs everything so it all adds up fast. Prefer to save where possible.
Depending on what your voyaging plans are I would stay away from a barometer that required some input from outside the boat, i.e. cell phones.

Many portable GPSs (i.e. Garmin) have models with a barometer function in them.

They will all vary from one another but the important information you gather from them is the trend over time alerting you of significant weather change.

~ ~ _/) ~ ~ MJH
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