News from CambridgeIC

How does resonant inductive sensing work?

While we were at the SPS show recently we took the opportunity to shoot a short video that demonstrates the basic operation of a CambridgeIC system.

We take a short look at how resonant inductive position sensing works, how our customers work with us and why. 

Turns out a noisy show isn't the easiest place to record a conversation, so we've also transcribed the video below. The next demo video will be shot in a quieter location!

Transcript:

 

Hello I am Guido Gandolfo, Product Manager with MEV, and we are here at the booth from MEV at the SPS show in Nuremberg, Germany. And with me is David Ely, hi David! 

And I’m director of Cambridge Integrated Circuits, CambridgeIC in Cambridge England. 

Welcome to our booth, and you wanted to show me what products you bought. 

Of course yes. So this is our development kit here and this is demonstrating our CAM204 chip working with three linear and one rotary inductive position sensors connected back to the chip. And this chip is reporting the position of one, two, three, four sensors - three linear and one rotary. It’s a non contacting sensor so I can remove them and put them back - they will operate across the gap between the sensor and the target. I can increase the gap on this target and the sensor still works, so its full non contact. 

So all of these sensors are made from printed circuit boards. They’re connected back to the CAM204 chip and the principle of operation is, inside these targets is a resonant circuit, a little inductor and capacitor and the chip energises them by sending current through the sensor coils which creates a magnetic field which energises the targets and then the sensor listens back for signals from the targets and those pass back to the chip, the chip processes those signals, calculates position and then sends it over a digital interface - in this case this is an interface box for a PC but for a normal customer application this would be connected to a microprocessor, micro controller inside the product. 

OK that’s very interesting. So the sensor is only a PCB, is that right? 

That’s all there is to it, a PCB measuring the position of, in this case, what we call standard targets. which has a wound rod and a capacitor inside and this is in a fully sealed unit that’s also available from CambridgeIC. 

And these sensor boards, do you provide them also? 

We sell samples of the sensor boards, but it’s much more common for customers to build them themselves. So we provide customers with the electronic file defining the coil positions and the shape of the coils in a Gerber format and customers can integrate that on their own circuit boards with their own connectors and mounting features, and connect those onto the chip that they mount on the circuit board in the final product. 

Is it a very expensive solution? 

Customers are using this to replace some very expensive components like optical encoders and particularly absolute optical encoders, even high resolution angle encoders, linear encoders are very difficult to get at a reasonable price so certainly our customers are happy to use our solution because its a dramatic reduction in cost and it simplifies their mechanics as well. 

Very interesting. Thank you David. 

Thank you for promoting our products at SPS. It’s good to see you.