captouch production testings

[HeGi_2497906]

We have completed the design of our CSD liquid level sensing solution based on PSoC4, it works great, and we can easily detect levels, temperature has minimal effect and we are satisfied with our design.

Now production has asked us to provide a solution to test the unit.  Our sensors are connected via wires, and the main board with the CPU is what is to be tested.

We need advice on how we can test to see if the capsense is functional?  Test engineering wants to put 50mil diameter pads connected to the traces, please confirm that this will not be a good idea as this will add stray capacitance?  Also, we are not sure what signal they could inject to determine if the captouch was working.  Also, I am skeptical that a precision capacitance can be shown to ask the unit to detect.

Below is a view of the connectors for the off board widgets, the pad shown on J1 is being requested on either side of the PCB.

Do you have any ideas or suggestions on how to production test this solution.  We do have one idea, to model the capacitance of the PCB with no connections and then again with a connector removed and another with the resistor removed and a third with a different resistive value.

[BragadeeshV · Accepted solution]

Hi HeGi_2497906​,

We are glad that your solution is working as per your expectation.

We would like to understand what sort of production tests you would like to perform on the units. Will the test be conducted with the sensors connected to the main boards using wires or do you want to perform these tests without the sensors connected?

We would recommend you to use the Built in Self test to check if there are any issues with the sensor hardware such as

1. sensors to sensor short

2. sensor to ground/ VDD short

3. Cp within limits test,

4. Cmod within limits test

5. Check if the rawcounts is within expected limits. For a given IDAC value, you could expect the raw count to be within certain limits. If you find your rawcounts to be abnormally high/ low / zero/ saturated, you could take that as a failure

Refer capsense component datasheet for details.

Regards,

Bragadeesh