Chapter 1: Things you need to know before you start working with SENSE

Use the latest version Google Chrome

SENSE is a web based software. In order for you to work with it you simply need access to a robust internet connection and Google Chrome installed in your computer.

SENSE was developed and tested to work optimally with Google Chrome. Using any other browser cannot guarantee proper user experience or simulation performance.

So, before starting to work with SENSE, make sure that you have the latest version of Google Chrome installed.

Canvas lags - hardware acceleration

In Google Chrome, hardware acceleration is a feature that allows the browser to access the device graphics hardware to speed up processes, thus improving the overall user experience when surfing the internet.

In case you are experiencing laggy behaviour in the different screens of SENSE, you are advised to activate hardware acceleration.

To do that follow the steps below:

  1. Click on the “Customize and control Google Chrome”

2. Choose “Settings”

3. Scroll down until you find the “Use hardware acceleration when possible” setting

4. Activate “Use hardware acceleration when possible”

Chapter 2: Things you need to know while you are preparing an analysis

How to design the DXFs for SENSE

If you want to learn how to prepare your .dxf file please read the comprehensive guide here

Should I center every element at the (0,0) in the Layout canvas?

SENSE’s Layout canvas is a 10x10m area where you can import or draw any sensor of your choice.

You do not need to place your sensor design at the (0,0) position. You are advised, however, to maintain good control of the positioning of your elements, since their distances, shapes and sizes are the parameters influencing their capacitance and resistance values.

I made a Layout and Pointers. What should I do for the analysis?

Once you make a Layout, build your StackUp and create your Pointer, you are ready to start the Analysis.

Simply navigate to the Analysis option in the Physical Model and choose which analysis you want to run.

About setting the dielectric constant of my finger. Normally what value should be?

There are two pointer options in SENSE:

The first one is needed for the Electrostatic Simulation.

Here the pointer is considered a perfect conductor, there is no dielectric involved. This is a standard practise, usually followed by laboratory tests, where the robotic touches are metal probes. You have, of course, the option to place a glove around the pointer. That glove can be any dielectric of your liking, in order to capture any different glove out there.

Using a pointer like this for the Electrostatic Simulation, the results will show how a metal probe changes the mutual and self capacitances of the sensor.

The second one is needed for the Spice Analysis.

Here you need to replicate the Human Body Model and create an electrical connection between your pointer and the ground. If you do not choose this option, your pointer will be considered floating, like a coin over a sensor. The most common representation of this type of pointer is a capacitance in series with a resistance (usually 100 pF and 1500 Ω).

Having those two pointer options, you first establish the influence of any pointer to the capacitances of the sensor and then you decide where this pointer is electrically connected to.

I can't find the pointer placement menu

The Pointer creation and placement options are located next to each other in the Pointers sections.

Once you create your pointer, simply select the Placements option and you will place the created pointer over your sensor.

For the analysis, we should assign parts as active. What does active mean? Does it mean that the part we assign active will be simulated and the part we do not will not?

That is partially correct.

In an Electrostatic Simulation, the result is a capacitance matrix.

A capacitance matrix consists of capacitance columns. Each column represents an active conductor and there you will find its self capacitance and the mutual capacitance to all other conductive parts.

This means that everytime you select a second active part, you ask SENSE to simulate a second capacitance column.

The more active parts selected, the more the simulation will last. The time increases linearly, 2 parts will take twice as much time

"Assign as Active" and still not sure what to do to get it to move to the next step. I picked one but still can't move on

To assign an Active conductor click on an Entity on the screen (1), Click on the Assign As Active (2) button and then click Next (3).

How can I set the ground in the stackup

To set a ground place in the StackUp of SENSE you first need to Add or Import it.

Then in the StackUp screen, you need to place it to the correct position.

Finally you need to assign its properties.

When we simulate a mutual capacitance between electrode 1 and electrode 2, should we assign both as active?

You do not need to assign both electrodes as active to simulate their mutual capacitance. One active Electrode will provide all the mutual capacitances to other conductive parts and its self capacitance in the form of a column.

Is there a reason to change permittivity and resistance of material like ITO/Ag Nano/metal mesh etc?

Changing the relative permittivity influences the capacitance results and changing sheet resistance influences the resistance results. You should always make sure you are using the correct values for your simulations, otherwise the results will not reflect reality.

Is there a way of specifying which side of the board the conductors are on?

The position of the conductors on a PCB board is determined by their position in the StackUp screen.

Here is a placement of electrodes and hatch shield on the top and traces and solid shield on the bottom of the board

How can I add a rectangle? If I put a rectangle on top of the sensor, will it work having an overlap with other entities?

You can import a design and edit that design by adding an element from the library of SENSE. Just make sure that when an overlap occurs it is between the same entities. A trace over a trace, a shield over a shield etc

Will a pointer always be touching from the side of the "first" layer (Layer 1) or can it also be set to touch from the other side of the stackup?

The pointer is always placed on top of the first StackUp layer. The exact position on the Z axis can be defined in the Pointer Placements screen, where z=0 is the surface of the top layer. The top layer should not be a conductive layer, because if a conductor and the pointer are touching the simulation will not be completed.

Is it now possible in SENSE to have more than one material forming the traces?

Yes you can have more than one material forming the traces and/or any other conductive element. You simply need to create more conductive groups in the StackUp screen and assign each material to it accordingly

Is it OK if a Via is not fully covered by the conductive layer it is connected to

It is not necessary for the VIA to be fully covered by the conductive layers it is connected to. SENSE will recognise any partial overlap and build the 3D model accordingly.

Is there a way of defining the thickness of the conductive layers?

You can define the material of the conductors. As far as the thickness is concerned, they are considered thin conductors, surfaces.

Is there a way to draw a layout without importing a design?

You can design any touch sensor layout by using the predefined entities in SENSE.

Here’s how a sensor designed completely using SENSE looks like

If I wanted to just simulate the capacitance across some PCB tracks, what is the simplest way to do that?

You can simply import or add only the PCB tracks. Then you can run a Capacitance analysis.

However, removing components like shields, buttons, sliders, wheels etc. will reduce the accuracy of your results. Capacitance is dependent on the geometry of the sensor so removing some geometrical entities will simulate different results.

How do you specify which layer the tracks and the shield element go on? I have set up two test tracks with an outline, and I want to place a shield underneath the tracks.

When you design the layout, all conductive components are placed on the same plane (2D design).

You can place them in the 3D space by selecting their position inside a stackup of dielectrics (a PCB or touchscreen substrate, for example)

So for the shielding we mean it is connected to ground?

For a Capacitance analysis, it is irrelevant, as the calculation of the capacitances takes into consideration only the geometry and the material properties of the conductors and dielectrics.

For an Equivalent Circuit analysis, you can define your Shielding to be grounded (sink) or to be active (source).

Chapter 3: Things you need to know while running an analysis

Can I close the chrome tabs to run simulation? Or should let them open until it is done?

SENSE automatically saves your settings every time you move from one screen to another. On the bottom of the screen you can see the last time your settings were saved.

You can do that manually by clicking CTRL + s.

This means that after you submit an analysis, you can close the browser window. The analysis will continue until the simulation is complete and the results will automatically be loaded in the results screen.

Do you know why my projects are submitted, but not in progress?

SENSE allocates resources out of a defined pool of Cores and gigabytes of RAM.

This means that once the pool is depleted and all resources are occupied, an analysis will be shown in a "Submitted" status, until resources become available again.

For example, if you have a pool of 96 Cores and decide to use 40 Cores for an analysis, then 56 Cores will remain in the pool. Now, if you try a new Analysis and request more than 56 Cores, this Analysis will be placed in a "Submitted" status until the requested Cores become available. Finally, if during this time you request a third Analysis with less than 56 Cores, this Analysis will start normally in priority over the second analysis, since the requested resources are available.

You can also submit multiple analyses in the queue. The Analysis that will be selected next depends both on submission order and required resources. The first submitted analysis is checked first, if there are enough resources, it begins, else the second is checked and so on.

How do I see details from the progress of my analysis?

While an analysis is running in SENSE, you can easily follow the progress in the “Progress” screen

Here you can see how the simulation is split in the “Setup” of the simulation, the “Run Tasks” and the “Finish” jobs. “Setup” and “Finish” usually last just a few seconds or minutes, however, the “Run Tasks” are computationally heavier and require more time, since it is there that the simulations are performed.

In the “Tasks” section, you can see the different tasks during the project. You will see the No Pointer and Pointer tasks. Those tasks will run in series, using the Resources you selected when setting up the Analysis.

If you expand one of those Tasks, you are able to see that they are split into “Setup”, “Preprocessing”, “Simulation”, “Postprocessing” and “Finish” jobs.

“Setup” and “Preprocessing” are the jobs responsible for building the 3D model of the sensor.

“Simulation” is the job that calculates the results you requested in the Analysis settings.

“Postprocessing” and “Finish” are the jobs responsible for patching up the simulation results and visualizing them.

I have gotten to the analysis part, but it fails at 10%.

You can find possible reasons why your simulation fails at 10% here

Chapter 4: Things you need to know after an analysis is completed

How to understand capacitance results

Reading the capacitance results in SENSE is a simple task. First you need to go to the Results screen, where you have three selection boxes and an intuitive interface to guide you

If you want more information about, please read here or here.

Can you see my project online?

Security is of utmost importance for us and for this reason at Fieldscale we cannot see your project online in order to help you prepare a project or troubleshoot.

In case your simulation fails, there is an option for you to share some details to us, so we can troubleshoot.

First of all, read the FAQ section to make sure that your problem is not related to a known issue, but to also make sure that you set up your project properly.

If that’s not the case then, communicate with Fieldscale through the support button at the bottom right and state your problem.

A member of our support team will be there to help you. They will ask for your consent to access those details and request a URL. Using this URL we will be able to track the cause of the failure. Just navigate to the Failed Analysis section and send that URL to us. Please mind that our engineers are available during European working hours.

Can I export the project?

There are three items you can export from SENSE:

  • A representation of your layout in .dxf format (in um)

  • The netlist of your sensor, if you solved an Equivalent Circuit Analysis

  • A .csv file of your Capacitance Analysis results

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