diff --git a/slsDetectorSoftware/multiSlsDetector/multiSlsDetector.cpp b/slsDetectorSoftware/multiSlsDetector/multiSlsDetector.cpp
index b3e42951c..3801c90ce 100644
--- a/slsDetectorSoftware/multiSlsDetector/multiSlsDetector.cpp
+++ b/slsDetectorSoftware/multiSlsDetector/multiSlsDetector.cpp
@@ -5942,12 +5942,16 @@ void multiSlsDetector::readFrameFromReceiver(){
 
 		//all done
 		if(!numRunning){
+			// let main thread know that all dummy packets have been received (also from external process),
+			// main thread can now proceed to measurement finished call back
+			sem_post(&sem_endRTAcquisition);
+			// wait for next scan/measurement, else join thread
 			sem_wait(&sem_newRTAcquisition);
 			//done with complete acquisition
 			if(checkJoinThread())
 				break;
 			else{
-				//starting a new scan/measurement
+				//starting a new scan/measurement (got dummy data)
 				for(int i = 0; i < numSockets; ++i)
 					runningList[i] = true;
 				numRunning = numSockets;
diff --git a/slsDetectorSoftware/slsDetector/slsDetectorUtils.cpp b/slsDetectorSoftware/slsDetector/slsDetectorUtils.cpp
index 406268656..2771c78a7 100644
--- a/slsDetectorSoftware/slsDetector/slsDetectorUtils.cpp
+++ b/slsDetectorSoftware/slsDetector/slsDetectorUtils.cpp
@@ -58,6 +58,8 @@ int  slsDetectorUtils::acquire(int delflag){
 	//not in the loop for real time acqusition yet,
 	//in the real time acquisition loop, processing thread will wait for a post each time
 	sem_init(&sem_newRTAcquisition,1,0);
+	//in the real time acquistion loop, main thread will wait for processing thread to be done each time (which in turn waits for receiver/ext process)
+	sem_init(&sem_endRTAcquisition,1,0);
 
 
   bool receiver = (setReceiverOnline()==ONLINE_FLAG);
@@ -351,6 +353,11 @@ int  slsDetectorUtils::acquire(int delflag){
 	  else{
 		  if (stopReceiver() == FAIL)
 			  *stoppedFlag = 1;
+		  else {
+			  if (*threadedProcessing && dataReady) // threaded processing
+				  sem_wait(&sem_endRTAcquisition); // waits for receiver's external process to be done sending data to gui
+		  }
+
 		  //	  cout<<"***********receiver stopped"<<endl;
 	  }
 	  pthread_mutex_unlock(&mg);//cout << "unlock"<< endl;
@@ -504,13 +511,15 @@ int  slsDetectorUtils::acquire(int delflag){
   cout << "acquisition finished callback done " << endl;
 #endif
 
-  setAcquiringFlag(false);
   sem_destroy(&sem_newRTAcquisition);
+  sem_destroy(&sem_endRTAcquisition);
 
 #ifdef VERBOSE
   clock_gettime(CLOCK_REALTIME, &end);
   cout << "Elapsed time for acquisition:" << (( end.tv_sec - begin.tv_sec )	+ ( end.tv_nsec - begin.tv_nsec ) / 1000000000.0) << " seconds" << endl;
 #endif
+  setAcquiringFlag(false);
+
   return OK;
 
 }
diff --git a/slsDetectorSoftware/slsDetector/slsDetectorUtils.h b/slsDetectorSoftware/slsDetector/slsDetectorUtils.h
index d10cef66d..87df119ff 100644
--- a/slsDetectorSoftware/slsDetector/slsDetectorUtils.h
+++ b/slsDetectorSoftware/slsDetector/slsDetectorUtils.h
@@ -1000,7 +1000,10 @@ virtual int setReceiverSilentMode(int i = -1)=0;
   int (*progress_call)(double,void*);
   void *pProgressCallArg;
   
+  /** semaphore to let postprocessing thread continue for next scan/measurement */
   sem_t sem_newRTAcquisition;
+  /** semaphore to let main thread know it got all the dummy packets (also from ext. process) */
+  sem_t sem_endRTAcquisition;
 
 
 };