Add delay after PSU on to let it stabilize before measuring

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

spectrometer.py

@@ -3,6 +3,7 @@
 import argparse
 import json
 import sys
+import time
 
 from hpcs6500 import HPCS6500, find_hpcs_port
 
@@ -17,6 +18,7 @@ def measure():
     try:
         dev.identify()
         dev.psu_on()
+        time.sleep(0.5)
         reading = dev.take_reading(psu=False)
     finally:
         dev.psu_off()