Better missing units handling

cheta/tests/test_fetch.py

@@ -7,7 +7,7 @@
 from Chandra.Time import DateTime
 from cxotime import CxoTime
 
-from .. import fetch, fetch_eng
+from .. import fetch, fetch_eng, fetch_sci
 
 print(fetch.__file__)
 
@@ -542,6 +542,38 @@ def test_interpolate_time_precision():
     assert abs(dt_frac) < 0.001
 
 
+@pytest.mark.skipif(not HAS_MAUDE, reason="MAUDE server not available")
+def test_2tlev2rt_units_maude():
+    msid = "2TLEV2RT"
+    start = "2026:065:13:39:10"
+    stop = "2026:065:13:40:30"
+
+    with fetch.data_source("MAUDE"):
+        dat_cxc = fetch.Msid(msid, start, stop)
+        assert dat_cxc.unit == "count"
+
+        dat_eng = fetch_eng.Msid(msid, start, stop)
+        assert dat_eng.unit == "HZ"
+
+        dat_sci = fetch_sci.Msid(msid, start, stop)
+        assert dat_sci.unit == "count"
+
+
+def test_2tlev2rt_units():
+    msid = "2TLEV2RT"
+    start = "2026:065:13:39:10"
+    stop = "2026:065:13:40:30"
+
+    dat_cxc = fetch.Msid(msid, start, stop)
+    assert dat_cxc.unit == "count"
+
+    dat_eng = fetch_eng.Msid(msid, start, stop)
+    assert dat_eng.unit == "HZ"
+
+    dat_sci = fetch_sci.Msid(msid, start, stop)
+    assert dat_sci.unit == "count"
+
+
 def _assert_msid_equal(msid1, msid2):
     for attr in ("tstart", "tstop", "datestart", "datestop", "units", "unit", "stat"):
         assert getattr(msid1, attr) == getattr(msid2, attr)

cheta/units.py

@@ -72,6 +72,7 @@ def emit(self, record):
         ("ASEC", "arcsec"),
         ("DEG", "deg"),
         ("DEGPS", "deg/s"),
+        ("HZ", "count"),  # Strange equivalence but e.g. 2TLEV2RT
         ("KHZ", "kHz"),
         ("KM", "km"),
         ("KMPS", "km/s"),
@@ -314,7 +315,7 @@ def convert(self, msid, vals, delta_val=False, from_system="cxc"):
                     MSID, conversion[0], conversion[1]
                 )
             )
-
-        vals = converters[conversion](vals, delta_val)
+        else:
+            vals = converters[conversion](vals, delta_val)
 
         return vals