diff --git a/serial/essai.sh b/serial/essai.sh
index 0d9a601..1935161 100755
--- a/serial/essai.sh
+++ b/serial/essai.sh
@@ -5,7 +5,7 @@ DATAFILE="foo.dat"
 TMPFILE="/tmp/dd2data"
 
 IMAGE="graphe.png"
-NB_READ=160
+NB_READ=15000
 
 ./t -v -n ${NB_READ} -d ${DEVICE} | tee -a ${DATAFILE}
 
@@ -16,6 +16,7 @@ set grid
 set xdata 	time
 set timefmt 	"%s"
 set format x 	"%H:%M:%S"
+set yrange [-5.0 : 30.0]
 plot	"${DATAFILE}" using 1:2 title " foo" with lines, \
 	"${DATAFILE}" using 1:3 title " bar" with lines, \
 	"${DATAFILE}" using 1:4 title "quux" with lines, \