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# LDC1612EVM: LDC1612EVM sensor data streaming

Part Number: LDC1612EVM

Hi,

I am using the LDC1612EVM for linear sensing application.
The coil being used has the following parameters attached below:

The sensor inductance sampled  value has a baseline at 58uH and raw data value of 6413055.
Frequency set at 3.3MHz   .

I was expecting the baseline inductance to be at 7.5uH in the graph and increase/decrease according to the target movement.
Also I was expecting the raw data to be starting from 0.

Kindly help.

Thanks

• Ashrith,

I will look into your questions and update this thread by COB tomorrow.
Regards,
John

• Ashrith,

The equations describing the behavior of the raw data and offset can be found in sections 8.1.3 and 8.1.3.1 of the data sheet.
Equation 4 shows the relationship between the raw data and the sensor frequency:

which shows the raw data is unlikely to ever be zero.

Equation 6 may be useful for understanding the relationship  between the sensor frequency, the raw data, and an offset parameter CHx_OFFSET:

more detailed info is available in the LDC1612 data sheet.

The spreadsheet-based tool can provide a good starting point for inductance calculations, but you will sometimes need to iterate the coil design and the device settings.
We have some tools and app notes that can help with this.
If you haven't done so already, please see the Inductive Sensing FAQ Page for resources and frequently asked questions.
Optimizing L Measurement Resolution for the LDC161x and LDC1101 covers device setting tradeoffs for resolution.
LDC Sensor Design provides information on best practices for inductive sensors.
Simulate Inductive Sensors Using FEMM (Finite Element Method Magnetics) provides a tutorial on simulating an inductive sensor with FEMM, a free finite-element simulation tool available from the FEMM Home Page.

Regards,
John

• Hi John,

Thank you for providing the above docs for better understanding.
However there are a few things that would not match any of the theoretical values.

I am using coil F with the following specs :

When these values are input in the GUI configuration section , the GUI calculates a total inductance and frequency that does not match the coil specifications above.

I would like to know why is the LDC calculating a different Sensor inductance and frequency value other than the provided information.
How can I get the parameters right?
Also upon checking the amplitude, it was 2Vp and -1Vp.

Thank you

• Ashrith,

The coil design tools - online or spreadsheet -  give a starting point for the coil design.
Tweaking the design may be needed to reach the final goals.
Also, the goal of our LDC parts is to measure the change in inductance because of target or button movement.
They are not intended to measure the absolute inductance value, like with an LCR meter.

Regards,
John

• Ashrith,

I don't recall if we have discussed this in previous threads, but a large cache of inductive sensing information is available at the Inductive Sensing FAQ page. It references a number of app notes and other collateral that can help with questions.

Regards,
John