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LDC1614EVM: Challenges with Achieving Stable Resonance Frequency Readings for LDC1614EVM and 36mH Coils Using Capacitors

Tarek Mostafa

Prodigy 60 points

Part Number: LDC1614EVM

Greetings,

I am currently using the LDC1614EVM in conjunction with 36mH coils. To achieve a resonance frequency of 1.1kHz, I attempted to use a 560nF capacitor. Unfortunately, the resonance frequency readings are proving to be unstable, and the correct value for the coil is not being measured. My suspicion is that this may be due to the proximity of the cutoff frequency of 1kHz. I have tested this hypothesis using capacitors of 470nF and 330nF, but the same behavior persists.

I would greatly appreciate any recommendations or advice you may have regarding this issue.

Thank you kindly in advance.

over 1 year ago

0 John Miller - Sensing over 1 year ago

TI__Mastermind 33240 points

Tarek,

Are you able to monitor the sensor waveform with an oscilloscope and high impedance probe?

Regards,
john

0 Tarek Mostafa over 1 year ago in reply to John Miller - Sensing

Prodigy 60 points

Thank you for the reply .. I didn't but I will do based on your recommendation but may I ask what am I looking for when I measure the waveform? sorry if it's basic question

0 John Miller - Sensing over 1 year ago in reply to Tarek Mostafa

TI__Mastermind 33240 points

Tarek,

The signal should look like a half-wave rectified sinusoid with a period corresponding to the desired sensor frequency.
The waveform should start close to zero, and the peak value should correspond to the expected peak amplitude that results from the DRIVE_CURRENT settings and the sensor parameters.

Figure 58 of the data sheet gives and example, and an oscope screen shot from one of the EVM is shown below.

Regards,
John