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Freescale Semiconductor
Document Number: AN4853
Application Note Rev. 0, 01/2014
© 2014 Freescale Semiconductor, Inc.
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MKM14 Pressure Sensor with Current Loop
(4-20ma) Output
by: Petr Gargulak
1 Introduction
This application note explains the example of
how to use MKM14 device in non-electric
metering application. In this case, the MKM14
device is used in simple small pressure sensing
application with industry standard current loop
output 4-20 mA. The benefit of MKM14 is
precise Analog Front-End (AFE) is used for
reading the pressure sensor with small span of
differential voltage output. The next benefit of
MKM14 is good computing power on low-
power device. This enables implement
compensation technique, which is required for
low-cost uncompensated pressure sensor
devices (like MPX53 series), used in this
application.
Contents
1 Introduction ......................................................1
2 Board hardware .................................................2
2.1 Power source .............................................3
2.2 Board current measuring ...........................4
2.3 Output current load circuit ........................4
2.4 Sensor connection .....................................4
2.5 Current management .................................4
2.6 Bill of material ..........................................5
2.7 The board schematic .................................7
3 Software ............................................................9
3.1 Main loop ..................................................9
3.2 Pressure sensor read interrupt routine ..... 10
3.3 Output current shunt resistor read interrupt
routine 11
4 Conclusion ...................................................... 12
5 Revision history .............................................. 12
