diff --git a/htdocs/frontend/javascripts/frontend.js b/htdocs/frontend/javascripts/frontend.js
index ffdc021..f80898f 100644
--- a/htdocs/frontend/javascripts/frontend.js
+++ b/htdocs/frontend/javascripts/frontend.js
@@ -373,31 +373,22 @@ vz.entities.loadData = function() {
 				waitAsync(function(json) {
 					entity.data = json.data;
 					
+					if (entity.data.min !== null && entity.data.min < vz.options.plot.yaxis.min) { // allow negative values for temperature sensors
+						vz.options.plot.yaxis.min = entity.data.min;
+					}
+
+					
 					// update entity table
 					// TODO add units
-					if (entity.data.min) {
-						if (entity.data.min < vz.options.plot.yaxis.min) { // allow negative values for temperature sensors
-							vz.options.plot.yaxis.min = entity.data.min;
-						}
-					
-						$('#entity-' + entity.uuid + ' .min')
-							.text(vz.wui.formatNumber(entity.data.min[1]))
-							.attr('title', $.plot.formatDate(new Date(entity.data.min[0]), '%d. %b %h:%M:%S', vz.options.plot.xaxis.monthNames));	
-					}
-					if (entity.data.max) {
-						$('#entity-' + entity.uuid + ' .max')
-							.text(vz.wui.formatNumber(entity.data.max[1]))
-							.attr('title', $.plot.formatDate(new Date(entity.data.max[0]), '%d. %b %h:%M:%S', vz.options.plot.xaxis.monthNames));	
-					}
-					if (entity.data.average) {
-						$('#entity-' + entity.uuid + ' .average').text(vz.wui.formatNumber(entity.data.average));
-					}
-					if (entity.data.consumption) {
-						$('#entity-' + entity.uuid + ' .consumption').text(vz.wui.formatNumber(entity.data.consumption));
-					}
-					if (entity.data.tuples) {
-						$('#entity-' + entity.uuid + ' .last').text(vz.wui.formatNumber(entity.data.tuples.last()[1]));
-					}
+					$('#entity-' + entity.uuid + ' .min')
+						.text((entity.data.min !== null) ? vz.wui.formatNumber(entity.data.min[1]) : '-')
+						.attr('title', (entity.data.min !== null) ? $.plot.formatDate(new Date(entity.data.min[0]), '%d. %b %h:%M:%S', vz.options.plot.xaxis.monthNames) : '');
+					$('#entity-' + entity.uuid + ' .max')
+						.text((entity.data.max !== null) ? vz.wui.formatNumber(entity.data.max[1]) : '-')
+						.attr('title', (entity.data.max !== null) ? $.plot.formatDate(new Date(entity.data.max[0]), '%d. %b %h:%M:%S', vz.options.plot.xaxis.monthNames) : '');
+					$('#entity-' + entity.uuid + ' .average').text((entity.data.average !== null) ? vz.wui.formatNumber(entity.data.average) : '-');
+					$('#entity-' + entity.uuid + ' .consumption').text(vz.wui.formatNumber(entity.data.consumption));
+					$('#entity-' + entity.uuid + ' .last').text((entity.data.tuples) ? vz.wui.formatNumber(entity.data.tuples.last()[1]) : '-');
 				}, vz.drawPlot, 'data')
 			);
 		}
diff --git a/lib/Interpreter/Interpreter.php b/lib/Interpreter/Interpreter.php
index 72952ec..ca012d2 100644
--- a/lib/Interpreter/Interpreter.php
+++ b/lib/Interpreter/Interpreter.php
@@ -44,7 +44,8 @@ abstract class Interpreter {
 	protected $from;
 	protected $to;
 	
-	protected $rows;
+	protected $rowCount = NULL;
+	protected $tupleCount = NULL;
 
 	/**
 	 * Constructor
@@ -92,17 +93,19 @@ abstract class Interpreter {
 		}
 
 		// get total row count for grouping
-		$this->rows = $this->conn->fetchColumn($sql['rowCount'], array($this->channel->getId()), 0);
+		$this->rowCount = $this->conn->fetchColumn($sql['rowCount'], array($this->channel->getId()), 0);
 
 		// query for data
 		$stmt = $this->conn->executeQuery('SELECT ' . $sql['fields'] . $sql['from'] . $sql['where'] . $sql['groupBy'] . $sql['orderBy'], array($this->channel->getId()));
 
 		// return iterators
-		if ($sql['groupBy'] || is_null($count) || $this->rows < $count) {
-			return new Iterator\DataIterator($stmt, $this->rows);
+		if ($sql['groupBy'] || is_null($count) || $this->rowCount < $count) {
+			$this->tupleCount = $this->rowCount;
+			return new Iterator\DataIterator($stmt, $this->rowCount);
 		}
 		else {
-			return new Iterator\DataAggregationIterator($stmt, $this->rows, $count);
+			$this->tupleCount = $count;
+			return new Iterator\DataAggregationIterator($stmt, $this->rowCount, $count);
 		}
 	}
 
@@ -198,6 +201,7 @@ abstract class Interpreter {
 	 */
 
 	public function getEntity() { return $this->channel; }
+	public function getTupleCount() { return $this->tupleCount; }
 }
 
 ?>
diff --git a/lib/Interpreter/MeterInterpreter.php b/lib/Interpreter/MeterInterpreter.php
index aec6dfe..f74e837 100644
--- a/lib/Interpreter/MeterInterpreter.php
+++ b/lib/Interpreter/MeterInterpreter.php
@@ -37,8 +37,7 @@ class MeterInterpreter extends Interpreter {
 
 	protected $min = NULL;
 	protected $max = NULL;
-	protected $consumption = NULL;
-	protected $tuples = NULL;
+	protected $pulses = NULL;
 	protected $resolution;
 	
 	/**
@@ -46,9 +45,9 @@ class MeterInterpreter extends Interpreter {
 	 * @return float total consumption
 	 */
 	public function getConsumption() {
-		if (is_null($this->consumption) && is_null($this->tuples)) throw new \Exception('Data has to be processed first!');
+		if (is_null($this->pulses) && is_null($this->tupleCount)) throw new \Exception('Data has to be processed first!');
 		
-		return $this->consumption / $this->resolution;
+		return $this->pulses / $this->resolution;
 	}
 
 	/**
@@ -56,7 +55,7 @@ class MeterInterpreter extends Interpreter {
 	 * @return array (0 => timestamp, 1 => value)
 	 */
 	public function getMin() {
-		if (is_null($this->min) && is_null($this->tuples)) throw new \Exception('Data has to be processed first!');
+		if (is_null($this->min) && is_null($this->tupleCount)) throw new \Exception('Data has to be processed first!');
 		
 		return $this->min;		
 	}
@@ -66,7 +65,7 @@ class MeterInterpreter extends Interpreter {
 	 * @return array (0 => timestamp, 1 => value)
 	 */
 	public function getMax() {
-		if (is_null($this->max) && is_null($this->tuples)) throw new \Exception('Data has to be processed first!');
+		if (is_null($this->max) && is_null($this->tupleCount)) throw new \Exception('Data has to be processed first!');
 		
 		return $this->max;
 	}
@@ -89,9 +88,8 @@ class MeterInterpreter extends Interpreter {
 	public function processData($count, $groupBy, $callback) {
 		$pulses = parent::getData($count, $groupBy);
 
-		$this->tuples = count($pulses);
 		$this->resolution = $this->channel->getProperty('resolution');
-		$this->consumption = 0;
+		$this->pulses = 0;
 
 		$tuples = array();
 		$last = $pulses->rewind();
@@ -109,7 +107,7 @@ class MeterInterpreter extends Interpreter {
 				$this->min = $tuple;
 			}
 				
-			$this->consumption += $tuple[2];
+			$this->pulses += $tuple[2];
 
 			$tuples[] = $tuple;
 			$last = $next;			
diff --git a/lib/View/JSON.php b/lib/View/JSON.php
index adb8c55..76dd67e 100644
--- a/lib/View/JSON.php
+++ b/lib/View/JSON.php
@@ -224,15 +224,12 @@ class JSON extends View {
 				);
 			}
 		);
-		$min = $interpreter->getMin();
-		$max = $interpreter->getMax();
-		$average = $interpreter->getAverage();
-		$consumption = $interpreter->getConsumption();
-		
-		$this->json['data']['min'] = $min;
-		$this->json['data']['max'] = $max;
-		$this->json['data']['average'] = View::formatNumber($average);
-		$this->json['data']['consumption'] = View::formatNumber($consumption);
+
+		$this->json['data']['min'] = $interpreter->getMin();
+		$this->json['data']['max'] = $interpreter->getMax();
+		$this->json['data']['average'] = View::formatNumber($interpreter->getAverage());
+		$this->json['data']['consumption'] = View::formatNumber($interpreter->getConsumption());
+		$this->json['data']['count'] = $interpreter->getTupleCount();
 		if (count($data) > 0) $this->json['data']['tuples'] = $data;
 	}