Analog Meter for NRG #40 Anemometer

[CBabcock]

Can anyone recommend a circuit for directly connecting a NRG #40 anemometer to an off the shelf panel meter and somewhat accurately displaying windspeed?  I would like it to be self powered and not require an external source of power to energize any needed circuitry.  These anemometers produce a very low AC voltage and it's frequency is proportional to windspeed.  I've had a box full of these anemometers for years now and would like to use them.  I know that it has to be a do-able endeavor as Enertech used to display windspeed on their control boxes via a self powered analog meter.  The Maximum Vigilant (I believe that's it's name) meter that I have been using for years is also self powered.  Analog meters are much more fun to watch anyways compared to digital, if you ask me.  There are plenty of met towers being decommissioned in the recent years and these sensors are becoming increasingly available for cheap or free.  It would be great to put them to use without breaking the bank and I thought that this would be a good place to start.

Thanks for your help
Corey

[Flux]

I have always measured frequency with the NRG, using a 2917 tacho chip.

I think the voltage out is small and very high impedance, I have never tried driving a voltmeter direct.

You may manage something with a 50 or 100 microamp meter. I think germanium signal rectifiers are still around. These will introduce some non linearity in the low wind scaling but will be better than silicon. If you scale the meter to suit you should overcome most of the non linearity but the low end may be limited.

Flux

[kitestrings]

Analog meters are much more fun to watch anyways compared to digital, if you ask me.

I agree, unless it is on something that isn't moving about a lot, like say a volt meter.

You might send Neilho a PM.  He has quite a few parts and pieces form Enertech systems.  Possibly a meter that would work.

~ks

[Mary B]

I don't see a proportional voltage output, spec I saw was so many hertz per mph. An analog meter is not going to work well with this without some type of amplifier.

[kitestrings]

I'm not familiar with the NRG, but I recall the early Enertech turbine panels used a direct connected wind speed gauge.  The anemometers (Maxium, Maximum,?) produced both a voltage and frequency that was linear with respect to wind speed 0-60 hz ~= 0-100 (or a tad under) mph IIRC.  The intent of using frequency was to avoid having the reading affected by line loss and termination resistance which could affect voltage based readings.  They were very simple, however, they were also sensitive to interference if the cable was unshielded/ungrounded.

They later went to a voltage or milliamp based gauge through a control circuit board which also controlled the speed at which their induction turbines ran.

~ks

[electronbaby]

Hey Corey, welcome to the group!!

It really depends on which model of NRG#40 you have.  There are #40C  which has a proportional AC output voltage, there is a #40H which uses a hall effect sensor to output pulses (you have to supply an input voltage) and there is a #40R which has a two opposing magnets and a reed switch (two contact closures per revolution).

There are a few ways to get these different sensors to work. The easiest would be if you had a #40C and a very sensitive analog voltmeter (which you will have to calibrate the scale to mph or m/s)



RoyR
KB2UHF

[Flux]

I have just found the sheet that came with my 40C. It implies that it gives about 12v at 60 Hz but does say that the voltage is not proportional to wind speed. I suspect that despite this it will be close.

I would try to keep to a 50 microamp meter and you can always calibrate it with a variable speed fan against its frequency out, which is linear. Should be good enough for general purpose use.

Flux

[CBabcock]

Well, curiosity got the cat.  Yesterday, I opened up the panel meter that displays windspeed on my Enertech 1500's control box.  I was just looking for any clues as to what type of meter they had used but what I found was that there's a small circuit board tucked inside the meter itself.  The circuit is rather simple and consists of a transistor, resistor, capacitor and a trim pot.




The circuit board:



I carefully removed the board from the meter and took some notes and drew up a quick schematic.  My apologies if the symbols are not 100% accurate, I'm not the greatest with electronics.



In my research online it looks as though the 2N1414 transistor is an obsolete part.  Can anyone suggest an alternative?  The meter itself had 300 uA FS printed on it, so I'm assuming it would be a 300 uA Full Scale meter.  Any other mods to suggest to the circuit?  The aneo's that I have are the voltage / frequency type (not externally powered, no reed switches).  I believe they are the 40C.  The specs I found says that they put out 2 VAC at 60 Hz and 60 Hz equals 45.82 m/s (about 100 mph). 

Corey

[Flux]

I think your transistor is Germanium PNP and most replacements are probably obsolete. Not sure about N America and what was used, but Europe used the OC71 and similar series for many years in portable radios and small audio and many must be about in old equipment.

The germanium will have lower volt drop and better linearity than a silicon replacement.

Meter no problem, 300UA may be tricky to get but you can shunt a 50 or 100UA or just increase the value of the variable resistor.

Low wind speed end will be better than the simple germanium bridge rectifier but may not be that different.

Flux

[Mary B]

ebay has 4 NOS transistors http://www.ebay.com/itm/4-vintage-TEC-2N1414-germanium-NPN-transistors-Gold-plated-leads-hard-to-find-/380674867766

NTE probably has a cross reference but I do not have an up to date CD.