diff --git a/FLUKE-8840A/createImages b/FLUKE-8840A/createImages
index d9e19f2f30d664c3f041d8227d956df1fa91149c..58e798afa9bb07d5533b64a82948e622f8e73e77 100755
--- a/FLUKE-8840A/createImages
+++ b/FLUKE-8840A/createImages
@@ -53,6 +53,7 @@ digitFile[8]='digit-8.png'
 digitFile[9]='digit-9.png'
 digitFile[10]='minus.png'
 digitFile[11]='plus.png'
+digitFile[12]=$emptyCanvas
 
 NUM2CHAR[0]='0'
 NUM2CHAR[1]='1'
@@ -66,6 +67,7 @@ NUM2CHAR[8]='8'
 NUM2CHAR[9]='9'
 NUM2CHAR[10]='-'
 NUM2CHAR[11]='+'
+NUM2CHAR[12]='_'
 
 digitPos[1]='+158+173.65'
 digitPos[2]='+192+173.65'
@@ -89,7 +91,7 @@ value=""
 DPR=$((RANDOM % $NUMBER_OF_DIGITS + 1)) # random dot position (1..$NUMBER_OF_DIGITS)
 for (( i=1; i<=$MAX_DIGITS; i++ )); do
   if (( $i <= $NUMBER_OF_DIGITS )); then
-    R=$((RANDOM % 12)) # random digit number (0..11='0'..'+')
+    R=$((RANDOM % 13)) # random digit number (0..12='0'..'_')
     eval DIGIT$i=${digitFile[R]}
     value+="${NUM2CHAR[R]}"
     if [ $DPR == $i ]; then