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Motorola Sensor Device Data
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The calibration of this system is as follows. Refer to Table 1.
CAUTION: While installing or changing the proper jumpers
described by each step, power must be off. Reapply power to
read the display after jumpers have been installed in their
proper location for each step. In each step there is a few
seconds’ delay after switching the power on and before an
output is displayed. Steps 1 through 3 must be performed prior
to system being operational.
Calibration
1. The pressure range of the system must be established.
The present software installed in this design supports 15,
30 and 100 psi sensors. Using an MPXM2202GS sensor
(30 psi) for example, only jumper J2 should be installed.
After power is applied, the LCD should read “30.” Power
off the system prior to proceeding to step 2.
2. The total system offset, due to the sensor and A/D, must
be established for the software routine to effectively
calibrate. With power off, jumpers J1 and J3 should be
installed. Reapply power, and the LCD should respond
with “000.” The offset value measured in this step is thus
stored for use in circuit operation. Power off the system
prior to proceeding to step 3.
3. In this step, the system full scale span is calibrated. With
power off, install jumper J1 only. Now apply the full rated
pressure (30 psi for MPXM2202GS) to the sensor, power
on and ensure the display reads “FFF.” The full scale
span measured in this step is thus stored for use in circuit
operation. Power off the system prior to step 4.
Operation
4. Ensure power is off, and install jumpers J1, J2 and J3.
The system is now ready for operation. Simply apply
power and pressure to the sensor, and the LCD will
display the proportional speed above 5 mph, up to the
limits of the sensor.
REFERENCES
Burry, Michael (1989). “Calibration–Free Pressure Sensor
System,” Motorola Application Note AN1097.
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Freescale Semiconductor, Inc.
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