ADS1298R: Cautery Protection Required

Hi vignesh,

Welcome to our e2e forum! Can you expand a little on what you mean by 'cautery protection is required'? Are you looking for ways to filter the ECG data during cauterization procedures? Can you provide any detail on what sort of corruption you get during the procedure?

Hi Tom,

Sorry for delayed in the reply.

Hope you are doing good.

At the time of Surgery/ during cauterization procedures, we are seeing only noises in the ECG waveforms using ADS1298R. These electro surgical noises should be removed to display the proper waveforms.

Please guide us to remove this noise.

Thanks and Regards,

Vignesh N

Hello Vignesh,

I hope that you are having a good day.

Can you provide an oscilloscope shot of the ECG waveforms before and after the cauterization test?

Are you using the RLD feature?

Can you provide a schematic?

Alexander Smith said:

Hello Vignesh,

I hope that you are having a good day.

Can you provide an oscilloscope shot of the ECG waveforms before and after the cauterization test?

Are you using the RLD feature?

Can you provide a schematic?xpstopdf (2).zip

Hi Smith,

Please find the schematic which we used in our product.

RLD Features:

We used RLD features. Please find the below configurations for ECG.

       write_ads1298r_reg(W_CONFIG1 , 0X86);  

            write_ads1298r_reg(W_CONFIG2 , 0X20);              

           write_ads1298r_reg(W_CONFIG3 , 0XDC); //0XDE

             write_ads1298r_reg(W_LOFF ,    0X03);              //lead 5

            write_ads1298r_reg(W_CH1SET  , 0X50);  

            write_ads1298r_reg(W_CH2SET  , 0X50);  // Set all channels to input short

            write_ads1298r_reg(W_CH3SET  , 0X50);

            write_ads1298r_reg(W_CH4SET  , 0X50);

            write_ads1298r_reg(W_CH5SET  , 0X50);

            write_ads1298r_reg(W_CH6SET  , 0X50);

            write_ads1298r_reg(W_CH7SET  , 0X50);

            write_ads1298r_reg(W_CH8SET  , 0X50);

            write_ads1298r_reg(W_RLD_SENSP  , 0X02);  

            write_ads1298r_reg(W_RLD_SENSN  , 0X06);

            write_ads1298r_reg(W_LOFF_SENSP  , 0XFF);

            write_ads1298r_reg(W_LOFF_SENSN  , 0X02);  

            write_ads1298r_reg(W_LOFF_FLIP  , 0X00);

            write_ads1298r_reg(W_LOFF_STATP  , 0X38);

            write_ads1298r_reg(W_LOFF_STATN  , 0X00);

            write_ads1298r_reg(W_GPIO  , 0X00);

            write_ads1298r_reg(W_PACE  , 0X00);

            write_ads1298r_reg(W_RESP  , 0XF2);

             write_ads1298r_reg(W_CONFIG4 ,0X22);

             write_ads1298r_reg(W_WCT1  , 0XFA);

             write_ads1298r_reg(W_WCT2  , 0XE3);

Sorry, The Snapshot of ECG waveform is not available since it was happen/observed when the surgery procedure in the hospital.

Hello Vignesh,

Thank you for providing the schematic and device registers.

Since you cannot provide a screen capture, do you have any information on the type of noise that was produced by the electrosurgical equipment? If the noise is out of the ECG spectrum there may be a way to filter it out and maintain the ECG waveform.

1) You could increase the capacitor size of your anti-aliasing filter to adjust the cutoff frequency.
2) Make sure that the cauterization equipment is not causing your power supplies to collapse.
3) Check the reference to make sure its stable.

Hi Smith,

I will get back with screen shot of ECG Noise waveform sortly.

Is there any issues observed from Register configurations or circuit.

What kind of filters required to use this ADS1298R in the Operation Theater when the cautery and diathermy procedure.

What is the maximum cutoff Frequncy to be set in circuit to use in the Opetion Thater .


Thanks and Regards,
Vignesh N

Hi Vignesh,

I did not see any issues.

Where you set your filters cutoff frequency depends on the noise frequency of the electrosurgical devices and your frequency band of interest.

A spectral analysis plot is typically used to determine these frequencies.

Anti aliasing (RC) and digital filters are typically used.

Hi ,

Please find the attached video (or use below link -google drive)which will have the noise wavefrom at the time of using the cautrery machines.

Some time lead off data received when the machine is using with patients.

Please guide us to filter thease type of noise data. Please let me know if you have any clarifications in the video

drive.google.com/open

Thanks and Regards,

Vignesh N

Hi Vignesh,

Thank you for providing the video!

There are a couple things that could be going on here:

Since I see the ECG waveform slowly appear after the cautery probe is used, the voltage from the cautery probe could be saturating the inputs of the ADC. Try decreasing your gain to 1 and see if the square waves on the ECG waveform still appear.

Since you are using a lower sample rate, increase the RC filter capacitors by a factor of 100 to 4.7nF. This will bring the cutoff frequency to 1.5kHz which will help filter the noise.

There are system level possibilities which will be harder to diagnose such as noise appearing on the power supplies, reference, or ground. I would recommend trying the two suggestions above first.

Thanks Smith,

We will do modification and come back to you with details.

Thanks and Regards,

Vignesh N

Hello Vignesh,

I had an additional question, how is the cauterization device grounded?

I can hear the device when it is operating which makes me think that there is a grounding issue.

Hi Smith,

Normally they will use Grouding pad at the time of cautery procedure.

Please Refer this video for grounding pad. 

www.youtube.com/watch

Please update, if you found any additional information for filtering these kind of noises.

Thanks and regards,

Vignesh N

Hi Vignesh,

Excellent video, thank you for the link.

I will. Let me know when you have made changes to the design.

Hi Smith,

We tried with 1.5KHz cutt off. Still the same problem was observed.

Please guide us to proceed further .

Thanks and Regards,
Vignesh N

Hi Vignesh,

That is unfortunate, we will have to continue debugging!

Did you try reducing the gain of the ADC to 1 to see if the output is still fullscale?

Can you probe your power supplies, reference, and grounds of the system to see if there is an unexpected source of noise during operation?

Hi Smith,

Kindly find the attached images:

1.Battery condition_1.5khz

2.Power connected_1.5khz

After changed 1.5Khz  frequency, normal condition(without using cautery) also get disturbed when power connected see the image but in battery condition the waveforms are looks like perfect.

Before changed frequency , no problems were in power connected condition

Thanks and regards

Vignesh N

Hi Vignesh,

This is good information.

Can you probe your power supplies, reference, and grounds of the system to see if there is an unexpected source of noise during operation?

Hi smith,

 Hope you doing good.

 sorry for the delay in reply.

We checked power connection, generally whenever try to connect power cord(2 pin L and N) ECG wave-forms are with noise. 

Normally in battery condition OR 3 pin power cord connected, ECG Wave-forms are looking good.

BUT WHENEVER CAUTERY SURGICAL UNIT USED, TOTAL ECG WAVE-FORMS ARE COLLAPSED.

Kindly suggest us to reduce cautery noise issue by using any internal filters

Thanks,

Vignesh N

Hello Vignesh,

I am doing well, thank you. I hope that you enjoyed your weekend.

A 2 pin power cord is not grounded which explains why you are seeing noise.

I have suggested in multiple posts that you probe your power supplies, reference, and grounds of the system to see if there is an unexpected source of noise during operation of the cautery device.

Without additional information I am unable to help.

At this point I do not believe that this is an internal filter issue with the ADC, but a system level issue related to your power supplies and grounding scheme.