diff --git a/build_sdcard.sh b/build_sdcard.sh
index ea3fdf8ae..fcbc597c0 100644
--- a/build_sdcard.sh
+++ b/build_sdcard.sh
@@ -252,6 +252,9 @@ sudo apt-get install -y autossh
 # see https://github.com/rootzoll/raspiblitz/pull/334
 sudo apt-get install -y fbi
 
+# prepare for powertest
+sudo apt install -y sysbench
+
 # prepare dor display service
 # see https://github.com/rootzoll/raspiblitz/issues/88#issuecomment-471342311
 sudo apt-get install -y redis-server
diff --git a/home.admin/config.scripts/blitz.powertest.sh b/home.admin/config.scripts/blitz.powertest.sh
index 882701663..b35028a92 100644
--- a/home.admin/config.scripts/blitz.powertest.sh
+++ b/home.admin/config.scripts/blitz.powertest.sh
@@ -3,21 +3,20 @@
 # Based on https://github.com/bamarni/pi64/issues/4#issuecomment-292707581
 # sysbench manual: http://imysql.com/wp-content/uploads/2014/10/sysbench-manual.pdf
 
+# check if bechmarking tool is installed
 sysbenchInstalled=$(sysbench --version 2>/dev/null | grep -c 'sysbench 0.')
 if [ ${sysbenchInstalled} -eq 0 ];then
   sudo apt install -y sysbench
 fi
-clear
 
-echo ""
-echo "***"
-echo "RaspiBlitz powertest v0.1"
-echo "Starting sysbench to run for 60 seconds (--max-time=60 --cpu-max-prime=10000)"
-echo "***"
-echo ""
+# do debug outputs to the STDERR - so that the STDOUT is just the results in the end
+echo "RaspiBlitz powertest v0.1" >&2
+echo "Starting sysbench to run for 60 seconds (--max-time=60 --cpu-max-prime=10000)" >&2
 
-sysbench --max-time=60 --test=cpu --cpu-max-prime=10000 --num-threads=4 run & # > /dev/null 2>&1 & 
+# starting bench mark
+sysbench --max-time=60 --test=cpu --cpu-max-prime=10000 --num-threads=4 run 1>/dev/null 2>&1 & 
 
+# keep monitoring in the background
 Maxfreq=$(( $(awk '{printf ("%0.0f",$1/1000); }'  </sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq) -15 ))
 for (( n=0; n<15; ++n )); do
 	Temp=$(sudo vcgencmd measure_temp | cut -f2 -d=)
@@ -25,9 +24,9 @@ for (( n=0; n<15; ++n )); do
 	SysFSClockspeed=$(awk '{printf ("%0.0f",$1/1000); }' </sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq)
 	CoreVoltage=$(sudo vcgencmd measure_volts | cut -f2 -d= | sed 's/000//')
 	if [ ${RealClockspeed} -ge ${Maxfreq} ]; then
-		echo -e "${Temp}$(printf "%5s" ${SysFSClockspeed}) MHz  ${CoreVoltage}"
+		echo -e "${Temp}$(printf "%5s" ${SysFSClockspeed}) MHz  ${CoreVoltage}" >&2
 	else
-	  	echo -e "${Temp}$(printf "%5s" ${RealClockspeed})/$(printf "%4s" ${SysFSClockspeed}) MHz ${CoreVoltage}"
+	  	echo -e "${Temp}$(printf "%5s" ${RealClockspeed})/$(printf "%4s" ${SysFSClockspeed}) MHz ${CoreVoltage}" >&2
   	fi
 	sleep 5
 done
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