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I would like to build a home weather station with analog instruments showing for example temperature, wind speed and wind direction.

I would like to use a salvaged flight instrument to show the wind direction: I have a wind vane transducer that convert the wind direction in an electrical signal and I would like to use this signal to drive a suitable instrument.

The instrument I have in mind is like a magnetic compass but while the magnetic compass does not need an "input signal" I need to drive the needle.

I have a look at a heading indicator

enter image description here

but it seems to me that the "airplane needle" is fixed while the 0-360 graduation is moving. I need, like in a compass, a fixed graduation and a moving needle.

For example this seems fine to me but I have no idea what instrument is:

MASCO SERV. CORP. DALLAS, TEXAS PART NO. 503A SER NO. 2500 enter image description hereenter image description here enter image description here

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  • $\begingroup$ The title asks one thing, but the body seems to ask another. Do you want to identify what instrument is that? Do you want to know if there is some model of electrical compass? Something else? $\endgroup$ – Federico Sep 10 '17 at 18:26
  • $\begingroup$ @Federico I am interested in answers to the title question. The instrument I posted is just an example. What is an electrical compass? $\endgroup$ – Alessandro Jacopson Sep 10 '17 at 20:36
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    $\begingroup$ Does your transducer output digital or analog angle values? If this is the later, you likely need some amplification to adapt the transducer output voltage and power to the input range of the instrument used for display, and correct the linearity. Solutions exist in the actuator world and your best friend is a small stepper motor with an analog-digital converter (if the sensor output is digital and the phase coding is compatible, you will only need the digital portion). $\endgroup$ – mins Sep 11 '17 at 6:55
  • $\begingroup$ @mins My transducer output analog 4-20mA signal. $\endgroup$ – Alessandro Jacopson Sep 12 '17 at 6:26
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Your best bet is to try and use an ADF readout, also known as a Fixed Card ADF (its most likely what you have pictured in your question). There are a few variants of the display out there and it will require some hacking to make it do what you need but it should suffice. As these units are generally considered "older" technology you may be able to get a read out for fairly cheap. On the even older side you can look for a Radio Compass/Radio Direction Finder which is quite similar.

Note: A heading indicator is NOT what you want. While you could pull one apart and install some kind of drive system to make it do what you want it is not, as it stands what you want.

enter image description here

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    $\begingroup$ The issue with these is that they use a synchro or resolver type interface. You'll need a matching synchro or resolver generator at the sensor to make them work together. Aside from availability, standards for synchros are 'flexible' which means that unless you have a matched pair, getting them to work together is a major headache. $\endgroup$ – Gerry Sep 10 '17 at 22:36
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Full Flight Simulators have compasses that are driven by electrical signals, not earth magnetic fields. There are quite a few older type sims such as B737-200 being scrapped, you could get a good deal there.

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