Wind Sensor Rev.P usage questions

Questions about Modern Device and JeeLabs Sensors
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detroit54
Posts: 1
Joined: Mon Mar 12, 2018 9:40 am

Wind Sensor Rev.P usage questions

Post by detroit54 » Mon Mar 12, 2018 9:52 am

Hi, I am using a Wind Sensor Rev.P with an Arduino MEGA 2560 R3. I am powering the sensor from 12.4V. I have noticed with the sensor sitting on my desk in a breadboard, oriented vertically, I regularly see speeds around 1.22 mph without any fans operating. With an 80mm DC fan operating, I see around 10 mph. The temperature reported by the sensor is always in the range of 40C or higher.

1. What is that temperature reading? I am wondering if it is due to the vertical orientation and something on the PCB heating the rising air below, or if it is actually measuring the temperature of a heated element on the sensor itself. i.e. should that sensor be showing me the actual room temperature, which is 24C?

2. I read in the blog here that someone was working on a temperature/humidity correction for this sensor, but I can't find anything else that shows how I might implement that. Has anyone actually finished that project?

3. My final question is about housing this sensor for use. I plan to use this sensor near a 4" diameter PVC exhaust pipe operating at 130 cfm. Which parts of this sensor need to be exposed? I am thinking only the loop and the thin "mast" next to it (for lack of a better word) need to be placed in the air stream, and I should be able to enclose the rest of the PCB in a small 3d printed housing similar to a USB stick. Does that seem correct?

Thanks,

Dan

paul
Site Admin
Posts: 735
Joined: Mon May 12, 2008 4:19 pm

Re: Wind Sensor Rev.P usage questions

Post by paul » Tue Mar 13, 2018 3:51 pm

Dan
I am using a Wind Sensor Rev.P with an Arduino MEGA 2560 R3. I am powering the sensor from 12.4V. I have noticed with the sensor sitting on my desk in a breadboard, oriented vertically, I regularly see speeds around 1.22 mph without any fans operating. With an 80mm DC fan operating, I see around 10 mph. The temperature reported by the sensor is always in the range of 40C or higher.

1. What is that temperature reading? I am wondering if it is due to the vertical orientation and something on the PCB heating the rising air below, or if it is actually measuring the temperature of a heated element on the sensor itself. i.e. should that sensor be showing me the actual room temperature, which is 24C?
There is an analog temperature sensor on the right hand "stalk" with the parts side facing you. The part is a MCP9701. It outputs an analog voltage which is not scaled at all - only buffered. The right hand stalk does suffer from some heating from the "cold side compensation" thermistor, and the temp sensor may also self-heat a half a degree. Also the absolute accuracy of the temp sensor is only ±2°C degrees. Still 40 degrees seems pretty far out of range. Put the fan facing the temp sensor and see if it reads something more accurate. Also you can find the math for the temp sensor in the datasheet.
2. I read in the blog here that someone was working on a temperature/humidity correction for this sensor, but I can't find anything else that shows how I might implement that. Has anyone actually finished that project?
There is a new regression at the end of the blog post. https://moderndevice.com/news/calibrati ... egression/

The only thing I erred on I think - is correcting your actual zero wind measurement to the zero wind value in the regression. I think you should just add a dummy amount to bring your (measured) zero wind value - to the value in the regression.
3. My final question is about housing this sensor for use. I plan to use this sensor near a 4" diameter PVC exhaust pipe operating at 130 cfm. Which parts of this sensor need to be exposed? I am thinking only the loop and the thin "mast" next to it (for lack of a better word) need to be placed in the air stream, and I should be able to enclose the rest of the PCB in a small 3d printed housing similar to a USB stick. Does that seem correct?
Yes, enclose the electronics and let the "stalks" stick out. You could also cut off the stalks on the line between the two sets of headers and then join the two sets of header with wires. We suggest tin snips for doing this amputation. Good luck.

Paul

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