diff --git a/backend/lib/controller/datacontroller.php b/backend/lib/controller/datacontroller.php
index 1af6dda..0d51e18 100644
--- a/backend/lib/controller/datacontroller.php
+++ b/backend/lib/controller/datacontroller.php
@@ -32,7 +32,7 @@ class DataController extends Controller {
 
 		$from = (isset($this->view->request->get['from'])) ? (int) $this->view->request->get['from'] : NULL;
 		$to = (isset($this->view->request->get['to'])) ? (int) $this->view->request->get['to'] : NULL;
-		$groupBy = (isset($this->view->request->get['groupBy'])) ? $this->view->request->get['groupBy'] : 400;		// get all readings by default
+		$groupBy = (isset($this->view->request->get['groupBy'])) ? $this->view->request->get['groupBy'] : NULL;	// get all readings by default
 
 		foreach ($channels as $channel) {
 			$this->view->addChannel($channel, $channel->getPulses($from, $to, $groupBy));
diff --git a/backend/lib/model/channel.php b/backend/lib/model/channel.php
index b207a09..06cca9f 100644
--- a/backend/lib/model/channel.php
+++ b/backend/lib/model/channel.php
@@ -88,6 +88,9 @@ abstract class Channel extends DatabaseObject implements ChannelInterface {
 				break;
 
 			default:
+				if (is_numeric($groupBy)) {
+					$groupBy = (int) $groupBy;
+				}
 				$sqlGroupBy = false;
 		}
 
@@ -116,7 +119,7 @@ abstract class Channel extends DatabaseObject implements ChannelInterface {
 		$reading = $result->rewind();
 		for ($i = 1; $i <= $packageCount; $i++) {
 			$package = array('timestamp' => $reading['timestamp'],	// last timestamp in package
-								'value' => $reading['value'],		// sum of values
+								'value' => (float) $reading['value'],		// sum of values
 								'count' => ($sqlGroupBy === false) ? 1 : $reading['count']);						// total count of values or pulses in the package
 
 			while ($package['count'] < $packageSize) {
diff --git a/backend/lib/view/jsonview.php b/backend/lib/view/jsonview.php
index 1da824b..5290bf8 100644
--- a/backend/lib/view/jsonview.php
+++ b/backend/lib/view/jsonview.php
@@ -60,7 +60,7 @@ class JsonView extends View {
 			$channel['unit'] = $obj->unit;
 			$channel['description'] = $obj->description;
 			$channel['resolution'] = (int) $obj->resolution;
-			$channel['costs'] = $obj->cost;
+			$channel['costs'] = (float) $obj->cost;
 			
 			// TODO check for optional data in second param
 			if (!is_null($data) && is_array($data)) {
diff --git a/share/tools/tests.php b/share/tools/tests.php
index 6b3f065..ef6b67c 100644
--- a/share/tools/tests.php
+++ b/share/tools/tests.php
@@ -23,7 +23,7 @@ include '../../backend/init.php';
 
 $meter = current(Channel::getByFilter(array('id' => 1)));
 
-$data = $meter->getData(0, time()*1000);
+$data = $meter->getPulses(1270062000000, 1270666800000, 400);
 
 echo '<table border="1">';
 foreach ($data as $i => $reading) {