WMR928N barometer offset

I’ve just hooked up a new WMR928N to replace my old WM918.

9.61e appears to be misreading the barometer. The sensor and console are both currently showing 1000mb, but WD is displaying 939mb. If I enter a +61mb offset WD shows the right numeric value. The barometer scale on the graph is wrong though. All the numbers are shifted down with the lowest barometer scale value lining up with the top of the Windspeed/Direction graph. See

http://www.weather-watch.com/blackpool-weather/layton.html

for an example. I think the graph line is roughly at the right value if the scale was in the right place.

Chris,
Looks like you had quite an unusual event around 19:30 hrs, your graphs all across the board took quite a jink…did you try going back a version or two and see if the problem persisted?
Jon

9.61e appears to be misreading the barometer. The sensor and console are both currently showing 1000mb, but WD is displaying 939mb. If I enter a +61mb offset WD shows the right numeric value. The barometer scale on the graph is wrong though. All the numbers are shifted down with the lowest barometer scale value lining up with the top of the Windspeed/Direction graph.l I think the graph line is roughly at the right value if the scale was in the right place.
Hi Chris, Does your WMR928N console show the raw (uncorrected) barometer reading? If it does you may try setting WD barometer offset to zero and compare the two. I think the two readings should be the same. Then try resetting the graph. Exit and save WD. Restart WD. Shut down Windows. Start windows. Wait a while and see what happens. :?
Looks like you had quite an unusual event around 19:30 hrs, your graphs all across the board took quite a jink.
I should put a health warning on the page. The new system isn't live yet. All the external sensors are sat on the floor waiting to be fitted outside, so a lot of the readings on the page won't be sensible. The unusual event was me fiddling with the baromter offset to try to correct the problem.

The next oldest version of WD that I’ve got is something like 9.34. My system has been off since early December, so 9.61e was the first update I’d collected for 3 months.

Does your WMR928N console show the raw (uncorrected) barometer reading?

I assume you mean corrected for my altitude? I’ve not set up an offset in the WMR928 yet because I’m not exactly sure of the height here. It’s not going to be significant though…I’m probably less than 100ft ASL!

With the 928 console showing 1000mb, WD was showing 939mb with the WD barometer offset at zero. I had to set the WD offset to 61 to get WD to show the same reading as the console. I’ve tried resetting the graph. I’ve tried restarting WD. I’ve rebooted the PC. :cry:
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I agree, you need to know what your elevation is. There has to be someone out there that has that information, Topographic maps? Then I would see if the local weather has their barometic pressure. you might be close and you would have something to compare to.

I have a different station, the davis vp and it requires the settings of elevation as well as coordinates for the latitude and longitude.

I would be sure that the elevation settings on your weather station and the WD match. and that any offsets are completed.
This is the tricky part getting the settings right. Do you know anyone who has a GPS, or something.

I should have made myself clearer. I can find out my elevation, it’s just that I’ve not checked yet. I’ve got a GPS, but they’re notoriously inaccurate for elevation readings.

The local METAR station (ENGH) is just under 3 miles away and they’re currently reading 1012 to my 1010. EGNH is 10m ASL and as the highest point within 10 miles (not my house) is only 30m ASL, I’m between 10 and 30m ASL! Without checking an accurate map I’d have have thought that ground level here is probably around 20m ASL. The barometer sensor is in the loft, so that’s another 8m which fairly accurately accounts for the 2mb difference between me and EGNH (20m = 2mb drop).

2mb isn’t bad

hi
the barometer offset of 61mb is correct
wd uses the raw value from the wmr968
i could have used the sea level adjsuted value, but its too late now, it would upset everyone.
make sure you are usign 9.61e as the new barometer graphign should be OK to handle large barometer swings like that.

the barometer offset of 61mb is correct make sure you are usign 9.61e as the new barometer graphign should be OK to handle large barometer swings like that.

Any idea why the offset is 61mb? It’s seems like a weird number to choose. Also if this offset is always required, is it possible to make it automatic for the WMR968/928? It fooled me for a while!

I am using 9.61e, but the graph did some weird things when the wild swings were happening. As I reported the scale shifted down so that the lowest value was level with the top of the wind graph. The scale has sorted itself out now that the wild swing has gone away.

each persons offset will be different, depending on there height above sea level, and the factory calibration
the next time you get a wild swing etc, zip and email me the latest.inf file from the datafiles folder
thanks

I got to know, what is that thing on the top of your head?

Some of my staff got me a duck hat ( a duck with feet , er webbies, and the other parts) on their last trip to Kansas City. But yours is interesting.

I got to know, what is that thing on the top of your head?

Some of my staff got me a duck hat ( a duck with feet , er webbies, and the other parts) on their last trip to Kansas City. But yours is interesting.

It’s a stuffed toy snake, the kind that babies play with :bday:

I was messing around with my eldest son (now six) and put the snake on my head to make him laugh. Unfortunately my wife caught me on camera :oops:

each persons offset will be different

I’m still puzzled about this. The offset of 61mb is required to force WD to display the same value that the barometer sensor and console display. I’m only a couple of millibar above sea level at the most and I’ve not set the sea level adjust in the station console, so the corrected and uncorrected values should be identical. The WMR918 protocol description suggests that both the sea level and local readings are transmitted, so as I’ve not set an offset in the console, surely the value displayed on the console is what WD should be receiving for both values? This of course assumes that the WMR928 uses the same protocol.

Also, it wasn’t a wild swing. WD displayed a value 61mb below the console value from the moment I connected them up. The wild swing was created when I added the 61mb offset to correct the problem.