Tizen Developers

Yes, It is possible to access them continuously and record them in memory.

As an option, You can develop a Tizen Web Application for that and Use HRMRawData Sensor API and FileSystem API. I am sharing a Code example, which will read HRM raw sensor data and store data on a txt file. The Interval is set to 500ms in the example.

var HRMrawsensor = tizen.sensorservice.getDefaultSensor("HRM_RAW");

function writeToFile(sensorData){
        
        tizen.filesystem.resolve("documents/testData.txt", function(testFile) {
        	 testFile.openStream("a", onOpenSuccess, null, "UTF-8"); //open file in append mode
        	 	
        	function onOpenSuccess(fs){            	
        		fs.write(sensorData.lightIntensity + " ");      // write sensor data to file
        		// opt/usr/media/documents 
            	fs.close();
           }
        });
    }

    
function onGetSuccessCB(sensorData){
    // pass sensorData to write to file
	   writeToFile(sensorData); 
}

function onerrorCB(error){
   console.log("error occurred:" + error);
}

function onsuccessCB(){
   console.log("HRMRaw sensor start");	   
   HRMrawsensor.getHRMRawSensorData(onGetSuccessCB, onerrorCB);
   HRMrawsensor.setChangeListener(onGetSuccessCB, 500,1000);
   // onGetSuccessCB function called at 500 ms Interval, batch latency 1000ms
}
	
function createFile(){
	var documentsDir,testFile;
		
    tizen.filesystem.resolve("documents", function(result) { // get to default document directory
    	documentsDir = result;
    	testFile = documentsDir.createFile("testData.txt");
	});
}
	

   
createFile();   //create the file
HRMrawsensor.start(onsuccessCB);    // start HRM raw sensor
    	

Add filesystem.read, filesystem.write, healthInfo privileges in config.xml.

You can check the file In Tizen Studio > Connection Explorer > Device > opt/usr/media/documents/testData.txt > Pull the file

Please check the Tizen Web Guides and Tizen Web API Documentations for details:

Device Sensor Guide

Sensor API

File System Guide

Filesystem API

​I'm also interested in this area, and would like to add a question to the topic. 
Do you know how where to find information about the max/min sampling intervals for each sensor? Fx. would it be possible to sample the PPG sensor with 25 Hz, i.e. sampling interval 40ms ? 

I would like to know where find this information too.
With the interval in the method setChangeListener is can configure the amount of time passing between 2 consecutive events (values from 10 to 1000 ms https://developer.tizen.org/ko/development/guides/web-application/sensors/device-sensors?langredirect=1), this means from 1 to 100 values per second but, are all this values a new sample of the PPG signal?

To sample the PPG sensor with 25 Hz, you just need to add the 40ms interval. Try this sample Code Instead:

    var HRMrawsensor = tizen.sensorservice.getDefaultSensor("HRM_RAW");
    
    function onGetSuccessCB(sensorData)
    {
        var date = new Date(Date.now());
    	var hours = date.getHours();
    	var minutes = "0" + date.getMinutes();
    	var seconds = "0" + date.getSeconds();   	
    	var ms = "0" +date.getMilliseconds();
    	var Time = hours + ':' + minutes.substr(-2) + ':' + seconds.substr(-2) + ':' + ms.substr(-3);
    	
    	console.log("data:" + sensorData.lightIntensity + " timeStamp:"+ Time);
	   //writeToFile(sensorData); 
	}

	function onerrorCB(error)
	{
	   console.log("error occurred:" + error);
	}

	function onsuccessCB()
	{
	   console.log("HRMRaw sensor start");	   
	   HRMrawsensor.getHRMRawSensorData(onGetSuccessCB, onerrorCB);
	   HRMrawsensor.setChangeListener(onGetSuccessCB, 40);
	}
    HRMrawsensor.start(onsuccessCB); 

And about "are all this values a new sample of the PPG signal?" seems Yes as per as I've seen the Documentations mentioned above.

yes, per as i have seen the Documentations i think so too.
thanks

Thanks a lot. I'll try it out