Reverse engineer inductance

[ssozonoff]

Hi Guys,

I am trying to build a PIC based controller for the trim tabs on my boat.

I bought the sensors for the tab position indicators without the electronics and I am trying to figure out how to interface these to a PIC. As seen in the picture the sensor is made up of a steel rod and a coil. There are only two wires coming from the sensor. I have no other information about these. Anyone have any suggestions about how I can figure out what the inductance of this sensor is? Could this be a half-bridge LVDT? The sensor is used to indicate position based on the lenght of rod in the coil.

Kind thanks for any pointers.

Serge

 

[Skogsgurra]

It works. I have used that technique in several appliances. Have been measuring thermistors using a simple capacitor. Relative humidity also. And location of core in simple coils as well as inductivity change in magnetostrictive material - makes a very simple and robust force transducer.

Typical cost for adding temperature and humidity "intelligence" to a bath-room fan is something like 10 cents in 1k+ volume (not counting thermistor and RH transducer).
You may have to do some homework before you apply this technique.

Gunnar Englund

http://www.gke.org

 

[ssozonoff]

Hi Gunnar,

I believe you and definately like the simplicity of the solution (KIS), thats why I am quizzing the heck out of you. I am simply very new to all this and trying to learn as much as possible.

So are you using a standard pic input or what?

I am definately trying to do my homework. With a lot of help from people like you of course.

Thanks,
Serge

 

[Skogsgurra]

OK, I will try and show you some measurements taken on an actual fan.

The circuit is a PIC output pin driving a capacitance via a thermistor, an RH transducer and a reference resistor. The waveforms look like this:

Maetpuls = measuring pulse.

Sorry, we are already wasting band-width. You have to do some tests on the bench now. Or simulate it.

Gunnar Englund

http://www.gke.org

 

[ssozonoff]

OK,

Thanks for your time and effort.

Serge