Index: trunk/ippMonitor/def/detProcessedExp.d
===================================================================
--- trunk/ippMonitor/def/detProcessedExp.d	(revision 18193)
+++ trunk/ippMonitor/def/detProcessedExp.d	(revision 19726)
@@ -16,5 +16,5 @@
 ARGS  ARG1 basename=$detProcessedExp.path_base
 
-OP    OP1  $detProcessedExp.bg / $detProcessedExp.bg_stdev
+# OP    OP1  $detProcessedExp.bg_stdev > 0.0 ? $detProcessedExp.bg / $detProcessedExp.bg_stdev : NAN
 
 #     field                    size    	format  name       show          link to                 extras
@@ -28,5 +28,6 @@
 FIELD detProcessedExp.bg_mean_stdev, 8,	%.3f,   [stdev],   value
 FIELD detProcessedExp.bg_stdev,   8,   	%.3f,   stdev,     value
-FIELD *,                          8,    %.3f,   S/N,       op=OP1
+FIELD (detProcessedExp.bg/detProcessedExp.bg_stdev), 8, %.3f,   S/N,     value
+# FIELD *,                          8,    %.3f,   S/N,       op=OP1
 FIELD rawExp.dateobs,            19,   	%T,     obs date,  value
 FIELD rawExp.filter,             10,   	%s,     filter,    value