Hi,

A few questions from a newbie regarding wind speed measurement. I have an ac generator wind sensor (RM Young) which gives only a few mV at low speed rising to several volts at high speed.

The frequency is the component read and I am seeing inconsistent results from a steady wind stream supplying a test bench sensor at around 4 knots. I see very steady results when connected to a competitor's weather logger.

Setup is DT80 using:

S1=0,0.1904,0,1"kts" RA("B:",ALARMS:OV:100KB,DATA:OV:1MB)10S LOGONA GA 1F(S1,"wind speed",250) 
1F("shaft frequency",250)

Is the above correct and what is the detection level for the inputs? Do I need to add some external signal conditioning to convert to TTL and then feed the HSC instead of the existing arrangement?

I ask this in preparation of later adding wind gust, which spawns a bunch of new questions for another query later... If there are any examples out there that use an ac sensor that I can study then info on these would be gratefully received. If this is best answered over some emails please do so.

Cheers,
Bill

Good afternoon Bill,

We recommend you connect it to the high speed counters 1 or 2 and use the low threshold channel option.

Cheers,
Roger

Hi Roger,

Thanks for the info. I have some more questions for you though.

I've now got some data but still wildly inconsistent and it looks like I will have to set up a signal generator to remove the sensor variability (Monday job).

I note the DT80 bible mentions the limit on the LT option is 7mV - do I need to protect these or are 1C-2C still good for 30V max even when LT is selected?

I also note p168 states the R channel option can be used to measure frequency: RA1S 1HSC(R,RS) - I've not found how to do this with Prog1.d80, can you assist?

As I asked previously, are there any wind speed examples you can offer?

Thanks,
Bill

Good morning Bill,

1. I would use a frequency generator to test the system. The wind sensor will not give consistent readings unless you have a calibrated wind tunnel to testing in.

2. The counters 1C and 2C are still rated to 30 VDC when in Low Threshold (LT) mode.

3. To set up the counters select Counter from the sensor list. Then where it says 1HSC click on the ... tab and select and check "Options Enabled" and check "Resetting"

Here is an example

BEGIN
RA1S
1HSC(R,RC)
END

Cheers,
Roger

Hi Roger,

Thanks for the info.

I'm still having some problems and hope you can help, as the DT80 I am testing is the first logger I am investigating for its suitability as a weather station - if I can't get it sorted and doing what is required dataTaker will miss out on the sale of many other units.

I don't wish to be overly critical but the manual leaves a lot to be desired in regard to showing newbies real-world examples. I did manage to see where you derive the R and RC from in your example but still can't invoke the RC from within the program unless I do it manually in the text field (even though I don't want to use it).

I am inputting a 10 Hz 50 mV square wave (555 timer source) in 1C with its ground connected to D Gnd, and with:

BEGIN
RA1S
1HSC(R,RS,LT)
END

I get:

2006/10/09 13:27:22 0.000366    1HSC    39.99512    Counts

which surprises me as I expected to see 10... but at least now I am seeing something reasonably consistent.

Can you please walk me through setting up a HSC for wind using a scale of knots = 0.1904 x Hz that will report every 10 minutes? I'd also like some idea of how I can record wind gust during this period. Wind gust being defined as the highest wind speed over a 3 second period during the ten minute logging time.

I don't have a problem reading and scaling all the other analog instruments I have connected, just this wind is a PITA.

Thanks for your patience and I look forward to your comments.

Regards,
Bill

Good morning Bill,

Exactly what model of wind sensor are you using? We want to test one here and want to make sure we are testing exactly the same type.

Cheers,
Roger

Hi Roger,

You took a little while to answer so I was hoping you were working in the background with the other guru's on this problem

The wind sensor is an RM Young Company model 05103 which is an ac generator type (rotating magnet cutting a coil, so is sinusoidal output varying in frequency and amplitude with speed). At low wind speed the amplitude is only a few millivolts so the LT option is necessary. See http://www.youngusa.com/

m/s = 0.0980 x Hz
knots = 0.1904 x Hz
mph = 0.2192 x Hz
km/h = 0.3528 x Hz

In your case you should do as you first suggested to me i.e. set up a signal generator as a test device.

I note on your web site dataTaker mention AN22 as a weather station and the pic shows what looks like to me as a Climatronics F460 wind speed and direction sensor attached to the system. This anemometer is a TTL square wave output also varying in frequency so fundamentally it should also be using the HSC's for its wind processing. Perhaps you could investigate how the author of that system did that for some help?

I hope this is sufficient information for you to assist and I look forward to your response once you have something.

Kind regards,
Bill

Just a quick note on this question.
There is a minor change to the hardware to read low threshold counter correctly.

Cheers,
Roger