ADS1298R: Problem i

Hello Harsh,

Thank you for your post.

The respiration waveform generally looks more sinusoidal when measured from the body. Do you still have the on-board MSP-generated waveform connected by chance? Also, check your electrode connections and ensure the lowest contact impedance possible. Is there a lot of impedance in the cables as well (from electrode connection to DB15 pin)?

Regards,

Ryan

Actually my hardware configuration is correct as per the data sheet photograph is as below

where jp34 and jp35 is Connection with LA ,RA Side and jp33 where channel 1 is selected for respiration mode. still not getting desired output. and in evm user manual there is mentioned about pulse mode which is not available in config 4 register, also vref bit is also not available in the data sheet. i think this is creating the difference in my output correct me if i am wrong.

can you please explain what is the interpretation of sine wave ? because most of places i have seen the respiration graph is like below.

Thank you in advance.

Hi Harsh,

The Pulse Mode and VREF to VREFP bit settings may be referring to features which we decided not to support at release. The EVM documentation should have been updated to reflect this since neither setting is mentioned in the production data sheet. My assumption is that those settings are controlled by the RESERVED bits. Please ensure that you are following the required settings for RESERVED bits (RESP[5] = 1b; CONFIG4[4, 0] = 0b).

Regards,

Ryan

I also done the same thing but not getting any sine wave or respiration signal.

Hi Harsh,

I'm still not sure what the issue is. Can you share the complete register map table showing the device configuration? 

Also, what is the cable impedance from the electrode connector to the DB15 pin on the EVM? 

The unfiltered respiration waveform should still be available to view under the normal Scope tab (CH1). Does the Respiration view and Scope view look the same (this is just to confirm the data is being handled properly in the GUI).

Regards,

Ryan

sorry for late reply below is the screenshot of register map and its value. Cable Resistance between electrode & DB15 is appx 10K.

additionally I observed one thing where when I connect JP34 - JP35 to LA and RA  then as per schematic of ads1298Recg-fe mentioned below where the significance of JP36 should be not there but in our module graph is changed in both case when JP36 connected or disconnected.

this is when jp36 is connected

when jp36 is not connect where i added both scope analysis without filter(scope window) and second one is with filter(respiration window). 

Hello, 

Yes I want to convey that when JP34 and JP35 is connected to LA & RA (connected to body) side then JP36 have not any significant to connect or disconnect. but in our setup as I have posted both screenshot there is change in waveform when we connect or disconnect JP36.

Hello Ryan, 

I have used both mode available on ADS1298R 1) Internal Respiratory Signal(MSP) with Onboard Circuitry. 2) Patient (simulator/ body) with Onboard Circuitry.

1) Internal Respiratory Signal(MSP) with Onboard Circuitry Results are as below.

(JP34) connected to (1-2)

(JP35) connected to (1-2)

(JP36) connected to (1-2)

                                 [scope analysis]

                               [Filtered Signal]

2) Patient (body) with Onboard Circuitry.

There is two different Results in this case where I have observed two different waveforms which is mentioned as below with their results.

i) (JP34) connected to (3-4) (Connected to Body)

   (JP35) connected to (3-4) (Connected to Body)

   (JP36) connected to (1-2) (Connected to MSP)

                            [Scope Analysis]

ii) (JP34) connected to (3-4) (Connected to Body)

    (JP35) connected to (3-4) (Connected to Body)

    (JP36) Not connected to (1-2) or (3-4) (Disconnected)

                             [Scope Analysis]

                         [ Filtered Signal ]

So I want to convey that I want to use ADS1298R with body and want to derive the respiration signal from Body. Currently as you can see that there is no respiration signal. what should i check or do further for getting respiration signal from body.

Impedance between DB15 Connector and Electrode is 10 K.

Hello Harsh,

The results from Case 1 look exactly as expected. The respiration impedance is modeled by the red dotted-line rectangle in Figure 36 of the User Guide. This circuit models the connection to the body as described in Section 5.2.1.

In Case 2 and 3, JP34 and JP35 are moved to the [2-3] position to connect Channel 1 to actual patient electrodes (RA and LA). The status of JP36 is irrelevant and is not required. JP36 is only used to control the U11 switch in the simulated patient circuit (Case 1). If you think the MSP control signal is coupling and interfering with the actual patient respiration measurement, then I recommend leaving JP36 uninstalled during those measurements. I have not come across that issue myself before, but I will check it again on our EVM setup.

When measuring respiration from an actual patient, you must ensure that the electrode contact impedance is minimal. Likewise, the 10k electrode cable impedance might be introducing too much noise in the respiration channel path. Can you try a cable with less impedance? 

Finally, the typical LPF order is higher than second-order. Can you set the LPF to 8th-order with 2-Hz cutoff?

One more suggestion - we typically see customers reduce the gain of the PGA to 2 to 4 V/V when measuring respiration. If the PGA gain is set to the default 6 V/V, you might saturate the channel. Section 10.2.1 of the data sheet details an applications design procedure for the respiration measurement.

Regards,

Ryan

Hello Ryan,

The results after changing the Electrode cable is as below where Impedance of this electrode is 2 ohm. But I have one question that I am previously using the cable which is come with ADS1298REVM kit (10k Impedance). so how can you manage it with ADS1298REVM kit ? and what is the recommended Electrode wire Impedance for ADS1298REVM ?

Hi Ryan,

1K works for me Thank you so much for guiding.