diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.h b/libraries/AP_InertialSensor/AP_InertialSensor.h
index 3697dbcc2b..2b52ccef58 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.h
@@ -113,8 +113,7 @@ public:
     /* get_delta_time returns the time period in seconds
      * overwhich the sensor data was collected
      */
-    virtual float get_delta_time() { return (float)get_delta_time_micros() * 1.0e-6; }
-    virtual uint32_t  get_delta_time_micros() = 0;
+    virtual float get_delta_time() = 0;
 
     // return the maximum gyro drift rate in radians/s/s. This
     // depends on what gyro chips are being used
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp
index dd45f67725..3eb6dd730b 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp
@@ -190,13 +190,7 @@ const uint8_t AP_InertialSensor_MPU6000::_temp_data_index = 3;
 int16_t AP_InertialSensor_MPU6000::_mpu6000_product_id = AP_PRODUCT_ID_NONE;
 AP_HAL::DigitalSource *AP_InertialSensor_MPU6000::_drdy_pin = NULL;
 
-// variables to calculate time period over which a group of samples were
-// collected
-// time period overwhich samples were collected (initialise to non-zero
-// number but will be overwritten on 2nd read in any case)
-static volatile uint32_t _delta_time_micros = 1;
 // time we start collecting sample (reset on update)
-static volatile uint32_t _delta_time_start_micros = 0;
 // time latest sample was collected
 static volatile uint32_t _last_sample_time_micros = 0;
 
@@ -304,7 +298,6 @@ void AP_InertialSensor_MPU6000::wait_for_sample()
 bool AP_InertialSensor_MPU6000::update( void )
 {
     int32_t sum[7];
-    uint16_t count;
     float count_scale;
     Vector3f accel_scale = _accel_scale.get();
 
@@ -320,17 +313,12 @@ bool AP_InertialSensor_MPU6000::update( void )
             _sum[i] = 0;
         }
 
-        count = _count;
+        _num_samples = _count;
         _count = 0;
-
-        // record sample time
-        _delta_time_micros = _last_sample_time_micros
-            - _delta_time_start_micros;
-        _delta_time_start_micros = _last_sample_time_micros;
     }
     hal.scheduler->resume_timer_procs();
 
-    count_scale = 1.0 / count;
+    count_scale = 1.0 / _num_samples;
 
     _gyro.x = _gyro_scale * _gyro_data_sign[0] * sum[_gyro_data_index[0]] * count_scale;
     _gyro.y = _gyro_scale * _gyro_data_sign[1] * sum[_gyro_data_index[1]] * count_scale;
@@ -659,9 +647,9 @@ void AP_InertialSensor_MPU6000::_dump_registers(void)
 
 
 // get_delta_time returns the time period in seconds overwhich the sensor data was collected
-uint32_t AP_InertialSensor_MPU6000::get_delta_time_micros() 
+float AP_InertialSensor_MPU6000::get_delta_time() 
 {
-    return _delta_time_micros;
+    return _msec_per_sample * 0.001 * _num_samples;
 }
 
 // Update gyro offsets with new values.  Offsets provided in as scaled deg/sec values
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
index c2278fa286..a91547d632 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.h
@@ -45,7 +45,7 @@ public:
     uint16_t            num_samples_available();
 
     // get_delta_time returns the time period in seconds overwhich the sensor data was collected
-    uint32_t            get_delta_time_micros();
+    float            	get_delta_time();
 
 protected:
     uint16_t                    _init_sensor( Sample_rate sample_rate );
@@ -66,7 +66,8 @@ private:
     static AP_HAL::SPIDeviceDriver *_spi;
     static AP_HAL::Semaphore *_spi_sem;
 
-    uint8_t _msec_per_sample;
+    uint8_t 					_msec_per_sample;
+    uint16_t					_num_samples;
 
     float                       _temp;
 
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.cpp
index cdad3627f0..262f5db64d 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.cpp
@@ -107,8 +107,8 @@ float AP_InertialSensor_Oilpan::temperature() {
     return _temp;
 }
 
-uint32_t AP_InertialSensor_Oilpan::get_delta_time_micros() {
-    return _delta_time_micros;
+float AP_InertialSensor_Oilpan::get_delta_time() {
+    return _delta_time_micros * 1.0e-6;
 }
 
 /* ------ Private functions -------------------------------------------*/
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.h b/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.h
index 6399f2eca1..0965587084 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Oilpan.h
@@ -19,7 +19,7 @@ public:
     bool            update();
     bool            new_data_available();
     float           temperature();
-    uint32_t        get_delta_time_micros();    // get_delta_time returns the time period in seconds overwhich the sensor data was collected    
+    float        	get_delta_time();    // get_delta_time returns the time period in seconds overwhich the sensor data was collected    
     //uint32_t        get_last_sample_time_micros();  // last_sample_time - get time (in microseconds) that last sample was captured
     float           get_gyro_drift_rate();
 
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_PX4.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_PX4.cpp
index 4e4b0a644f..663fd2df19 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_PX4.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_PX4.cpp
@@ -105,9 +105,9 @@ float AP_InertialSensor_PX4::temperature(void)
     return 0.0;
 }
 
-uint32_t AP_InertialSensor_PX4::get_delta_time_micros(void) 
+float AP_InertialSensor_PX4::get_delta_time(void) 
 {
-    return _delta_time_usec;
+    return _delta_time_usec * 1.0e-6;
 }
 
 uint32_t AP_InertialSensor_PX4::get_last_sample_time_micros(void) 
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h b/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h
index 93ed71ccdd..b88bc527a5 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_PX4.h
@@ -23,7 +23,7 @@ public:
     bool            update();
     bool            new_data_available();
     float           temperature();
-    uint32_t        get_delta_time_micros();
+    float        	get_delta_time();
     uint32_t        get_last_sample_time_micros();
     float           get_gyro_drift_rate();
     uint16_t        num_samples_available();
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp
index ea6c43a65f..c5ac267169 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Stub.cpp
@@ -35,8 +35,8 @@ bool AP_InertialSensor_Stub::new_data_available( void ) {
 float AP_InertialSensor_Stub::temperature() {
     return 0.0;
 }
-uint32_t AP_InertialSensor_Stub::get_delta_time_micros() {
-    return _delta_time_usec;
+float AP_InertialSensor_Stub::get_delta_time() {
+    return _delta_time_usec * 1.0e-6;
 }
 uint32_t AP_InertialSensor_Stub::get_last_sample_time_micros() {
     return _last_update_ms * 1000;
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Stub.h b/libraries/AP_InertialSensor/AP_InertialSensor_Stub.h
index b96ff108a7..39018c4fa3 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Stub.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Stub.h
@@ -17,7 +17,7 @@ public:
     bool            update();
     bool            new_data_available();
     float           temperature();
-    uint32_t        get_delta_time_micros();
+    float	        get_delta_time();
     uint32_t        get_last_sample_time_micros();
     float           get_gyro_drift_rate();
     uint16_t        num_samples_available();