Part Number: MSP430FR2633
Other Parts Discussed in Thread: CAPTIVATE-PHONE,
Hi,
We are currently evaluating CapTIvate capacitive sensing, and as part of our internal evaluation, we are testing its noise immunity against noise generated by an electrosurgical unit.
Because the noise generated by the electrosurgical device is not constant in either frequency or intensity, we believe it is similar to random radiated EMS noise.
During this evaluation, we observed that the CapTIvate count value fluctuates when the noise source is active. We would appreciate your advice on how to minimize this effect.
Below is a summary of our test setup and observations.
Test Overview
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Target: CapTIvate capacitive sensing
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Test method: Evaluation with an electrosurgical noise source placed near the sensor system
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Evaluation metric: Variation in the count value
Test Configuration
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We used MSP430FR2633 together with CAPTIVATE-PHONE.
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A tube was placed on Channel 9, E06 of numericKeypadSensor, which corresponds to part 8 in the attached image.
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Conversion Count was set to 300, and calibration was performed. All other parameters were left at their default settings.
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The tube was then filled with saline to complete the setup.
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Log acquisition was started, and noise was measured while operating the electrosurgical unit.
Electrosurgical Unit Test Conditions
We tested the following combinations of mode, setting value, and cable orientation relative to the electrode.
| Condition | Mode | Setting Value | Cable Orientation Relative to Electrode |
|---|---|---|---|
| 1 | Cut | 300 | Horizontal |
| 2 | Coag | 120 | Horizontal |
| 3 | Cut | 300 | Vertical |
| 4 | Coag | 120 | Vertical |
Observed Behavior
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Under normal conditions, the count value is stable.
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When the electrosurgical unit is operating, the count value sometimes fluctuates significantly.
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The magnitude of the fluctuation changes depending on the position and orientation of the noise source.
We will attach measurement graph for reference.
Currently Considered Hardware Mitigation
At the moment, the only hardware mitigation we are considering is adjusting the damping resistor values inserted in the transmit and receive lines.
However, if there are any recommended internal parameter settings in CapTIvate, such as filtering, averaging, or frequency-related settings, that could improve noise immunity, we would like to evaluate those as well.
Questions
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Are there any recommended CapTIvate configuration settings to improve noise immunity in this kind of random radiated noise environment?
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Are there any recommended hardware design practices to improve noise immunity?
Best regards,
Conor
