Hi Roger,

I am trying to log data from an anemometer (Anemometer standard 7911, from DAVIS INSTRUMENTS), which has 4 wires: - Black -> Wind speed contact closure to ground

• Green -> Wind direction pot wiper (360 deg = 20 kOhm)
• Yellow -> Pot supply voltage
• Red -> Ground

I have tested the anemometer and works properly. But when I connected to the DT800: * The resistance range change from 20 kOhm to 800 Ohm (while is linear, because there is one part near to 0 deg where the readings change arriving up to 5000 Ohms or more).

Channel 6 has been configured as a Resistance Input of two wires (Green Wire to 6Channel+, and Red Wire to 6Channel- and Sr).

Channel 5* has been configured as Frequency type with a threshold of 500 mV. Channel 5+ is connected to 5 V (provided by Sp, which is connected to Yellow Wire), and Channel 5- is connected to the Black Wire. P12 parameter has been set to 1000.

DT800 does not take any frequency (it sends -99999.90 Hz) but when I connect the terminals of a multi meter on the channel 5+, and channel 5- in order to see if the signal generated by the anemometer changes, then the DT800 takes proper readings (1-9 Hz, depending on the wind speed).

So it only works if I test the channel 5+, and channel 5- with the two terminals of a multi meter (in DC voltage) proving that the anemometer works providing a small pulse of supply voltage. The frequency signal depend on the wind speed. Any suggestion?

Thanks,
Josep

Good morning Josep,

May I please make a few suggestions on wiring?

1. Wire the Yellow to the + and the and the Green to the - and read the channel as a 2 wire resistance i.e. 1R(2W)

2. The pulse output of the anemometer is best read as a digital input to one of the high speed counters (Input 7 or 8). Wire the Black to Input 7 and the Red to the digital ground. Then read the counter with the reset option 7C(R)

Cheers,
Roger

Good Afternoon Roger,

I tried another connection configuration and it worked properly. Although, your configuration also works properly. But in both cases, sometimes the readings of the potentiometer are correct (0-20 Kohm) and sometimes are wrong (around 120 kOhm, 250kOhm or 380 kOhm depending on time and sometimes 0-15KOhm), and I don't know why.

Do you know the reason, and how could it be solved?

Many Thanks,
Josep

Good morning Josep,

In the specification sheet for the DT800 the maximum stated resistance we can read is 10 kOhms, While we can read resistance greater that that there are several things that make the reading less accurate.

You could try slowing down the AD converter speed allowing more setting time between reading. Try setting P60=20

Cheers,
Roger

Good morning Roger,

I have set P60=40,30,20,10. And It doesn't works properly. Any other suggestion?

Cheers
Josep

Good morning Josep,

In an earlier post you state "I tried another connection configuration and it worked properly" exactly what wiring configuration are you using and how are you reading it (Channel type)?
I want to set up some testing here to see if I can replicate the problem you are having

Cheers,
Roger

Good Morning Roger,

I tried another connection, changing the wiring. But at the end, I used exactly the connection you commented, with the type channels you said: 12R(2W) for potentiometer, and 7C(R) for wind speed

1. Wire the Yellow to the + and the and the Green to the - and read the channel as a 2 wire resistance -> 12R(2W)

2. The pulse output of the anemometer is best read as a digital input to one of the high speed counters (Input 7 or 8). Wire the Black to Input 7 and the Red to the digital ground. Then read the counter with the reset option -> 7C(R)

The wind speed works properly, but I have problems with the potentiometer how I stated in previous mails. Try to replicate the problem.

Thanks for your help,
Regards
Josep

Good morning Josep,

I have run some testing here with a high precision resistance source as a 2 wire configuration and the stability and accuracy I am getting is very good. 20,000 Ohms with +/- 3 Ohms noise. (well within specification)

I think you will need to look closer at the Pot in the device. Do you have a trim pot that you can wire in in the place of the wind vane? If that works the it will give you confidence that the dataTaker is working correctly. If it doesn't then we need to look more closely at the dataTaker.

Cheers,
Roger

Hello Roger,

I have connected a potentiometer of 100kohms to the DT800 in the place of the wind vane, and it works properly reading the correct figures. (the same figures measured with a multimeter DMM)

But with the wind vane doesn't works yet. It doesn't read the same as the multimeter do when I connect directly the multimeter to the wind vane wires (a linear response from 0 to 20 kohms). The response measured by the DT800 is not linear from around 13 kohms to 1 kohms, more or less.

It doesn't make sense!
Regards,

Good afternoon Josep,

That if it works with a pot connected but not the wind vane than that would suggest that there is something wrong with the wind vane.

Cheers,
Roger