Vectrino+ distance sensor

Hi,

I'm using the Vectrino+ for laboratory test ( http://www.nortekusa.com/en/knowledge-center/forum/velocimeters/182041836 ) and, recently, I'm experiencing a problem with the distance sensor. To set the Vectrino sampling volume height (with respect to the channel bottom) , I run a distance check and I adjust the Vectrino position on a moving "up-down" rail. It always worked well since yesterday. I want to place my sampling volume at a height Hsv=3cm from the bottom, so I need to set the sensor height at Hsens=8cm wright? The weird thing happening is that  for 5cm<Hsens<10cm the distance given as output is the double of the real distance. Once beyond Hsens=10cm it works well again.

I think that the sound speed is related to this problem, thus, even if I can know the exact position without using the distance sensor, my velocity results will be distorted.

Do you have an idea of what's happening?! (weak spot related problems? sound speed?)

The setting parameters I'm using:

acquisition frequency: 200Hz

nominal velocity range: 1m/s

transmitting length: 0.3

sampling volume: 4

sound speed fixed at: 1485m/s (pure water)

I hope you can help me!

Thank you very much in advance

Regards

Paolo Caccamo

Hi Paolo,

Sounds like you're doing it right. Sometimes the distance check picks up the wrong peak (typically an second echo an integral multiple of the actual distance). Take a look at the probe check and you can see if this is the case. Unfortunately, there's not a way in software to specify which peak to use for distance measurements.

When collecting data however, if you start disk recording before starting data collection with the Vectrino, the probe check output will be saved in the binary file. When exporting to ASCII you'll wind up with a *.pck file. You can use the information there to determine a distance measurement.

P.J.

Hi again,

thank you very much for your very fast answer.

Actually what you suggest is probably right, the probes miss the first peak and take the second one.

I thought that some parameters like the water temperature, salinity or density could play a role so I tested the Vectrino in different waters and my impression is that there's no connection between these parameters and the problem. What is very weird is that this malfunctioning appears only at some positions along the channel axis whereas nothing changes on the channel bottom.

Now, if this is the problem:

- how can I repair it?

- over all, do this problem influence velocity measurements? I mean, the distance values are useful to place the probe at the right height but not essential. But do this "echo problem" will have repercussions on velocity measurements?????

I send you a screen-shot of the probe check. I think that first peak is "less clean" than the second one. Receivers differs of more counts than in the second peak and maybe this is why it automatically take the second peak. You think is a receiver problem? Can I improve the four receivers signals ??

Thank you again

Regards

Paolo Caccamo

Previously Paolo Caccamo wrote:

- how can I repair it?

- over all, do this problem influence velocity measurements? I mean, the distance values are useful to place the probe at the right height but not essential. But do this "echo problem" will have repercussions on velocity measurements?????

I send you a screen-shot of the probe check. I think that first peak is "less clean" than the second one. Receivers differs of more counts than in the second peak and maybe this is why it automatically take the second peak. You think is a receiver problem? Can I improve the four receivers signals ??