diff --git a/secop_psi/SR_7270.py b/secop_psi/SR_7270.py
index e2934d0..765fa5e 100644
--- a/secop_psi/SR_7270.py
+++ b/secop_psi/SR_7270.py
@@ -54,7 +54,7 @@ class XY(HasIodev, Readable):
         'range': Parameter('sensitivity value', FloatRange(0.00,1,unit='V'), poll=True, default=1),
         'irange': Parameter('sensitivity index', IntRange(0,27), poll=True, readonly=False, default=25),
         'autorange': Parameter('autorange_on', BoolType(), readonly=False, default=True),
-        'tc': Parameter('time constant value', FloatRange(10e-6,1,unit='s'), poll=True, default=0.1),
+        'tc': Parameter('time constant value', FloatRange(10e-6,100,unit='s'), poll=True, default=0.1),
         'itc': Parameter('time constant index', IntRange(0,30), poll=True, readonly=False, initwrite=True, default=14),
         'nm': Parameter ('noise mode',BoolType(), readonly=False, default=0),
         'phase': Parameter('Reference phase control', FloatRange(-360,360,unit='deg'), poll=True, readonly=False, initwrite=True, default=0),