diff --git a/script/optics/ExitSlitYScanKei.py b/script/optics/ExitSlitYScanKei.py
index 8d5fd78b..85eca0b4 100644
--- a/script/optics/ExitSlitYScanKei.py
+++ b/script/optics/ExitSlitYScanKei.py
@@ -12,6 +12,7 @@ SENSORS = (Keithley1, Keithley2, MachineCurrent)
 STARTPOS = (-0.5)
 ENDPOS = (1.0)
 STEPS = 0.01
+NSTEPS = round((ENDPOS - STARTPOS) / STEPS) + 1
 LATENCY = 0.1
 DWELL = 1.0
 
@@ -21,13 +22,13 @@ KEI_RMU = "X03DA-KEITHLEY-2:"
 caput(KEI_DIODE + "READSCAN.SCAN", 0)
 caput(KEI_DIODE + "NPLC", 1)
 caput(KEI_DIODE + "NAVG", DWELL / 0.02)
-caput(KEI_DIODE + "TCOUNT", 1)
+caput(KEI_DIODE + "TCOUNT", NSTEPS)
 caput(KEI_DIODE + "RANGE", 6) # 200 nA
 
 caput(KEI_RMU + "READSCAN.SCAN", 0)
 caput(KEI_RMU + "NPLC", 1)
 caput(KEI_RMU + "NAVG", DWELL / 0.02)
-caput(KEI_RMU + "TCOUNT", 1)
+caput(KEI_RMU + "TCOUNT", NSTEPS)
 caput(KEI_RMU + "RANGE", 8) # 2 nA
 
 def trig():