diff --git a/lasp/device/lasp_device_common.py b/lasp/device/lasp_device_common.py
index 0790fdb..1ad2cec 100644
--- a/lasp/device/lasp_device_common.py
+++ b/lasp/device/lasp_device_common.py
@@ -19,8 +19,8 @@ class DaqChannel:
     def __post_init__(self):
         if len(self.channel_metadata) > 0:
             meta = json.loads(self.channel_metadata)
-            for key,val in meta.items():
-                setattr(self, key, val)
+            if '_qty' in meta:
+                self._qty = Qty.from_json(meta['_qty'])
         else:
             self._qty = SIQtys.default