DEMOAPEXSENSOR Freescale Semiconductor, DEMOAPEXSENSOR Datasheet - Page 10

• Manufacturer Part Number: DEMOAPEXSENSOR
• Description: BOARD DESIGN ALTITUDE PRESSURE
• Manufacturer: Freescale Semiconductor

Specifications of DEMOAPEXSENSOR

• Sensor Type: Accelerometer, Pressure, Water Level, Altimeter/Barometer
• Sensing Range: Multiple Ranges
• Interface: I²C, SPI, Analog
• Sensitivity: Multiple
• Voltage - Supply: 10 V
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: MPX2102, MPXV5004G, MPL115A2, MMA7361L
• Acceleration: 6 g
• Sensing Axis: Triple Axis
• Output Type: Digital
• Interface Type: I2C, SPI
• Operating Voltage: 16 V
• Operating Current: 10 mA
• Leaded Process Compatible: Yes
• Peak Reflow Compatible (260 C): Yes
• Rohs Compliant: Yes
• Silicon Manufacturer: Freescale
• Silicon Core Number: MPXM2102A, MPXV5004G, MPL115A2, MMA7361L
• Kit Application Type: Sensing - Sampling Kit / Related Components
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: MPL115A, MPXM102A, MPXV5004G

DEMOAPEXSENSOR Altitude Measurement
but on this demo board, the MPXM2102A pressure sensor has been used to get a high resolution for altitude measurement. The
MPXM2102A is an absolute pressure sensor. It measures the pressure on its port in relation to a vacuum sealed reference. The
specs given on the data sheet do not easily translate into creating a product that resolves 1m of height difference. The
DEMOAPEXSENSOR in this sense explores how a sensor can be amplified and put through a 24-bit delta sigma ADC to pursue
that type of application.
to improve the resolution the MPXM2102A. One method aims at a sub 1 foot increment, but this is not as stable as the 1m
increment method. Again, this is a experimental board and the method used to measure the MPXM2102A for altitude is subject
to many outside influences. These are not limited to, but include; sudden pressure changes, gusts of wind, A/C unit on/off cycling,
temperature, and exposure to high brightness light. Note the value is setup for dynamic change. The altitude absolute height is
not calibrated. This is typical of end application requiring a starting point.
Table 2. Operating Characteristics (V
the FSS is 40 mV for 100 kPa of applied absolute pressure. The DEMOAPEXSENSOR does not have a full 10V supply. The part
is biased instead by a 5V supply. This cuts the FSS to 20 mV for 100 kPa. Since the output of an analog sensor is ratiometric to
the input voltage, it is crucial to have a stable supply voltage. In the case of amplifying and analyzing small pressure changes,
the input voltage must be stable to remove input noise. To achieve this, a shunt voltage reference connected to the 5V regulator
provides a low noise, stable voltage of 4.096V for the MPX2102A. This is the IC, D8 on the demo schematic, and is typically used
for data-acquisition systems. Thus, the span is really only 16.38 mV at 4.096V, for a pressure range of 0 to 100 kPa. MPXM2102A
is on a separate shunt such that no other connected IC will induce additional noise on the shared line.
Sensors
Freescale Semiconductor
Differential Pressure Range
Supply Voltage
Supply Current
Full Scale Span
Offset
Sensitivity
Linearity
Pressure Hysteresis (0 to 100 kPa)
Temperature Hysteresis (-40°C to +125°C)
Temperature Coefficient of Full Scale Span
Temperature Coefficient of Offset
Input Impedance
Output Impedance
Response Time (10% to 90%)
Warm-Up Time
Offset Stability
There are two sensors that can be used for altitude measurement. The MPL115A can be used as an approximate altimeter,
There is more than one section in the software to determine the vertical altitude. The code has more than one method to try
Table 2
shows the typical operating characteristics of the MPXM2102A. The supply voltage is ratiometric, but at 10V supply,
Characteristic
S
= 10 V
MPXM2102D/G Series
MPXM2102D/G Series
MPXM2102A Series
MPXM2102A Series
MPX2102D Series
MPX2102D Series
MPX2102A Series
MPX2102A Series
DC
, T
A
= 25°C unless otherwise noted, P1 > P2)
Symbol
TCV
TCV
ΔV/ΔΡ
Z
V
V
V
P
Z
V
OFF
OFF
—
—
—
—
—
—
OUT
—
—
I
FSS
t
OP
O
IN
R
S
OFF
FSS
1000
1400
Min
38.5
-1.0
-2.0
-1.0
-2.0
-0.6
-1.0
-0.6
-1.0
-2.0
-1.0
—
—
—
—
—
—
—
—
0
Typ
±0.1
±0.5
±0.5
6.0
0.4
1.0
10
40
20
—
—
—
—
—
—
—
—
—
—
—
—
—
Max
2500
3000
41.5
100
1.0
2.0
1.0
2.0
0.4
1.0
0.4
1.0
2.0
1.0
16
—
—
—
—
—
—
—
mV/kPa
%V
%V
%V
%V
%V
%V
Units
mAdc
AN3956
kPa
V
mV
mV
mV
mV
ms
ms
W
W
DC
FSS
FSS
FSS
FSS
FSS
FSS
10