LDC1612EVM: Schematic or Layout

Hello Karim,

Let me comment on your questions here. Note that a lot of this information already exists in the datasheet and user's guide:

Karim Somani said:

I was hoping if you could provide me with a detailed version/breakdown of all the registers. Ideally, explaining what each register does and how the overall signal is detected. I would really appreciate a walk-through of the design, just how the signal flows through the system

There is a theory of operation section starting on page 36 of the LDC1612 datasheet which helps with understanding what the device is actually doing and how a typical sensor might operate. The device is basically converting the frequency of the LC sensor to a 28 bit digital value. The registers are all also detailed in the datasheet starting on page 17. We've also included a high Configuration page in the Sensing Solutions GUI (http://www.ti.com/lit/zip/snoc028). This allows you to more intuitively change the device functions and is outlined starting on page 24 of the LDC1612EVM User's Guide (www.ti.com/.../snou135): 

Karim Somani said:

I was also hoping if you could tell me will I be able to use the LDC1612EVM for particle detection. The size of the particles would be:

178 µm - 2540 µm (Ferrous particles)

508 µm - 1996 µm (Non-Ferrous particles)

I wouldn't expect this device to detect the smaller particles, but hopefully it can detected the bigger ones.

This sounds like it will be a challenging application especially if there is a large distance between the particle and the sensor. I would recommend reading the following blog: e2e.ti.com/.../inductive-sensing-target-size-matters

Karim Somani said:

I also had a question regarding how this device would perform if I had a solid object following though a tube with water. I am wondering if the device would detect the object or would it detect the water along with the object or not detect the object at all because of the water.

If the tube is rubber or plastic then you will see the conductive object flowing through, provided that it produces enough inductance change to be seen by the sensor. If the tube is metallic or conductive, then this will shield the LDC from seeing the small object. Note that we've demonstrated using the LDC devices to sense a rotating metallic impeller in a flow meter application. You can find a quick video showing the theory and demonstration of the flow meter using the LDC0851 device: www.youtube.com/watch

Karim Somani said:

I am also wondering if the flow rate would impact the ability of the device to detect an object. Say something passes buy it slow or fast we would also have to consider the size of what object being passed. I am also not sure what the range of the device is in terms of its ability to detect an object and be precise. 

Assuming that you are sampling fast enough then you should be able to distinguish between a small or large object based on the magnitude of inductance shift seen by the LDC. A small object moving slowly will still have a smaller signal change than a large object moving quickly.

Karim Somani said:

Another question I have is what level of impact would vibration and heat have on this device, does it create noise in the system and would that noise need to be filtered.

Heat will generally affect the capacitor due to the temperature coefficient. However, this is more or less a slow change, so if you are looking for when an object passes by the sensor then this usually occurs much faster and can be easily distinguished with a simple moving average.

Karim Somani said:

My last question is how is the waveform generated. I've noticed that the device itself picks up small noise so what was the method that you guys used to generate the signal, or is this just a raw single with no filtering. I'm asking this because it doesn't seem to be consistent when you hold the same object a fixed distance away from the device. 

This is again covered in the Theory of Operation section of the datasheet. The device is showing what the raw frequency of the LC tank looks like compared to a  40MHz reference oscillator included on the EVM. I would also recommend to read the following application note: 

• Optimizing L Measurement Resolution for the LDC161x and LDC1101

Regards,

Luke LaPointe