diff --git a/waveguide/waveguide.py b/waveguide/waveguide.py
index cbc9fe8..87324c3 100755
--- a/waveguide/waveguide.py
+++ b/waveguide/waveguide.py
@@ -907,7 +907,8 @@
     wifiblaster.enable         Enable WiFi performance measurement.
     wifiblaster.interval       Average time between automated measurements in
                                seconds, or 0 to disable automated measurements.
-    wifiblaster.measureall     Unix time at which to measure all clients.
+    wifiblaster.measureall     Unix time at which to measure all clients, or 0
+                               to disable measureall requests.
     wifiblaster.onassociation  Enable WiFi performance measurement after clients
                                associate.
 
@@ -938,6 +939,20 @@
     except ValueError:
       return None
 
+  def _GetParameters(self):
+    """Reads and returns all parameters if valid, or Nones."""
+    duration = self._ReadParameter('duration', float)
+    enable = self._ReadParameter('enable', self._StrToBool)
+    fraction = self._ReadParameter('fraction', int)
+    interval = self._ReadParameter('interval', float)
+    measureall = self._ReadParameter('measureall', float)
+    onassociation = self._ReadParameter('onassociation', self._StrToBool)
+    size = self._ReadParameter('size', int)
+    if (duration > 0 and enable and fraction > 0 and interval >= 0
+        and measureall >= 0 and size > 0):
+      return (duration, fraction, interval, measureall, onassociation, size)
+    return (None, None, None, None, None, None)
+
   def _SaveResult(self, line):
     """Save wifiblaster result to the status file for that client."""
     g = re.search(MACADDR_REGEX, line)
@@ -975,23 +990,18 @@
     """Return the time of the next measurement event."""
     return self._next_measurement_time
 
-  def Measure(self, interface, client):
+  def Measure(self, interface, client, duration, fraction, size):
     """Measures the performance of a client."""
-    enable = self._ReadParameter('enable', self._StrToBool)
-    duration = self._ReadParameter('duration', float)
-    fraction = self._ReadParameter('fraction', int)
-    size = self._ReadParameter('size', int)
-    if enable and duration > 0 and fraction > 0 and size > 0:
-      RunProc(callback=self._HandleResults,
-              args=[WIFIBLASTER_BIN, '-i', interface, '-d', str(duration),
-                    '-f', str(fraction), '-s', str(size),
-                    helpers.DecodeMAC(client)])
+    RunProc(callback=self._HandleResults,
+            args=[WIFIBLASTER_BIN, '-i', interface, '-d', str(duration),
+                  '-f', str(fraction), '-s', str(size),
+                  helpers.DecodeMAC(client)])
 
   def MeasureOnAssociation(self, interface, client):
     """Measures the performance of a client after association."""
-    onassociation = self._ReadParameter('onassociation', self._StrToBool)
+    (duration, fraction, _, _, onassociation, size) = self._GetParameters()
     if onassociation:
-      self.Measure(interface, client)
+      self.Measure(interface, client, duration, fraction, size)
 
   def Poll(self, now):
     """Polls the state machine."""
@@ -1005,29 +1015,33 @@
       # Inter-arrival times in a Poisson process are exponentially distributed.
       # The timebase slip prevents a burst of measurements in case we fall
       # behind.
-      self._next_measurement_time = now + random.expovariate(1 / interval)
+      self._next_measurement_time = now + random.expovariate(1.0 / interval)
 
-    interval = self._ReadParameter('interval', float)
-    if interval <= 0:
+    # Read parameters.
+    (duration, fraction, interval, measureall, _, size) = self._GetParameters()
+
+    # Handle automated mode.
+    if interval > 0:
+      if self._interval != interval:
+        # Enable or change interval.
+        StartMeasurementTimer(interval)
+      elif now >= self._next_measurement_time:
+        # Measure a random client.
+        StartMeasurementTimer(interval)
+        try:
+          (interface, client) = random.choice(self._GetAllClients())
+        except IndexError:
+          pass
+        else:
+          self.Measure(interface, client, duration, fraction, size)
+    else:
       Disable()
-    elif self._interval != interval:
-      # Enable or change interval.
-      StartMeasurementTimer(interval)
-    elif now >= self._next_measurement_time:
-      # Measure a random client.
-      StartMeasurementTimer(interval)
-      try:
-        (interface, client) = random.choice(self._GetAllClients())
-      except IndexError:
-        pass
-      else:
-        self.Measure(interface, client)
 
-    measureall = self._ReadParameter('measureall', float)
+    # Handle measureall request.
     if time.time() >= measureall and measureall > self._last_measureall_time:
       self._last_measureall_time = measureall
       for (interface, client) in self._GetAllClients():
-        self.Measure(interface, client)
+        self.Measure(interface, client, duration, fraction, size)
 
     # Poll again in at most one second. This allows parameter changes (e.g. a
     # measureall request or a long interval to a short interval) to take effect
diff --git a/waveguide/wifiblaster_controller_test.py b/waveguide/wifiblaster_controller_test.py
index 6b562b1..9e300f2 100755
--- a/waveguide/wifiblaster_controller_test.py
+++ b/waveguide/wifiblaster_controller_test.py
@@ -17,6 +17,7 @@
 
 import glob
 import os
+import random
 import shutil
 import sys
 import tempfile
@@ -102,6 +103,7 @@
   d = tempfile.mkdtemp()
   old_wifiblaster_dir = waveguide.WIFIBLASTER_DIR
   waveguide.WIFIBLASTER_DIR = tempfile.mkdtemp()
+  oldexpovariate = random.expovariate
   oldpath = os.environ['PATH']
   oldtime = time.time
 
@@ -110,6 +112,7 @@
     return faketime[0]
 
   try:
+    random.expovariate = lambda lambd: random.uniform(0, 2 * 1.0 / lambd)
     time.time = FakeTime
     os.environ['PATH'] = 'fake:' + os.environ['PATH']
     sys.path.insert(0, 'fake')
@@ -141,11 +144,6 @@
       WriteConfig('measureall', '0')
       WriteConfig('size', '1470')
 
-      # Disabled. No measurements should be run.
-      print manager.GetState()
-      for t in xrange(0, 100):
-        wc.Poll(t)
-
       def CountRuns():
         try:
           v = open('fake/wifiblaster.out').readlines()
@@ -155,16 +153,24 @@
           os.unlink('fake/wifiblaster.out')
           return len(v)
 
-      CountRuns()  # get rid of any leftovers
+      # Get rid of any leftovers.
+      CountRuns()
+
+      # Disabled.
+      # No measurements should be run.
+      print manager.GetState()
+      for t in xrange(0, 100):
+        wc.Poll(t)
       wvtest.WVPASSEQ(CountRuns(), 0)
 
+      # Enabled.
       # The first measurement should be one cycle later than the start time.
       # This is not an implementation detail: it prevents multiple APs from
       # running simultaneous measurements if measurements are enabled at the
       # same time.
       WriteConfig('enable', 'True')
       wc.Poll(100)
-      wvtest.WVPASSGE(wc.NextMeasurement(), 100)
+      wvtest.WVPASSGT(wc.NextMeasurement(), 100)
       for t in xrange(101, 200):
         wc.Poll(t)
       wvtest.WVPASSGE(CountRuns(), 1)
@@ -183,20 +189,16 @@
         wc.Poll(t)
       wvtest.WVPASSGE(CountRuns(), 1)
 
-      # Run the measurement at t=400 to restart the timer.
-      wc.Poll(400)
-      wvtest.WVPASSGE(CountRuns(), 0)
-
       # Next poll should be in at most one second regardless of interval.
-      wvtest.WVPASSLE(wc.NextTimeout(), 401)
+      wvtest.WVPASSLE(wc.NextTimeout(), 400)
 
-      # Enabled with longer average interval.  The change in interval should
+      # Enabled with shorter average interval.  The change in interval should
       # trigger a change in next poll timeout.
       WriteConfig('interval', '0.5')
       old_to = wc.NextMeasurement()
-      wc.Poll(401)
+      wc.Poll(400)
       wvtest.WVPASSNE(old_to, wc.NextMeasurement())
-      for t in xrange(402, 500):
+      for t in xrange(401, 500):
         wc.Poll(t)
       wvtest.WVPASSGE(CountRuns(), 1)
 
@@ -218,6 +220,7 @@
                               manager.GetState().assoc[0].mac)
       wvtest.WVPASSEQ(CountRuns(), 1)
   finally:
+    random.expovariate = oldexpovariate
     time.time = oldtime
     shutil.rmtree(d)
     os.environ['PATH'] = oldpath