3–236
Motorola Sensor Device Data
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EVALUATION BOARD DESCRIPTION
The information required to use evaluation board number
DEVB147 follows, and a discussion of the design appears in
the Design Considerations section.
FUNCTION
The evaluation board shown in Figure 1 is supplied with an
MPX2100DP sensor and provides a 100 kPa full scale
pressure measurement. It has two input ports. P1, the
pressure port, is on the top side of the sensor and P2, a
vacuum port, is on the bottom side. These ports can be
supplied up to 100 kPa (15 psi) of pressure on P1 or up to 100
kPa of vacuum on P2, or a differential pressure up to 100 kPa
between P1 and P2. Any of these sources will produce the
same output.
The primary output is a 10 segment LED bar graph, which
is labeled in increments of 10% of full scale, or 10 kPa with the
MPX2100 sensor. An analog output is also provided. It
nominally supplies 0.5 volts at zero pressure and 4.5 volts at
full scale. Zero and full scale adjustments are made with
potentiometers so labeled at the bottom of the board. Both
adjustments are independent of one another.
ELECTRICAL CHARACTERISTICS
The following electrical characteristics are included as a
guide to operation.
Characteristic
Symbol
Min
Typ
Max
Units
Power Supply Voltage
B+
6.8
—
13.2
dc Volts
Full Scale Pressure
PFS
PMAX
VFS
VOFF
—
—
100
kPa
Overpressure
—
—
700
kPa
Analog Full Scale
—
4.5
—
Volts
Analog Zero Pressure
Offset
—
0.5
—
Volts
Analog Sensitivity
SAOUT
ICC
IFS
—
40
—
mV/kPa
Quiescent Current
—
40
—
mA
Full Scale Current
—
160
—
mA
CONTENT
Board contents are described in the parts list shown in
Table 1. A schematic and silk screen plot are shown in Figures
2 and 6. A pin by pin circuit description follows.
PIN-BY-PIN DESCRIPTION
B+:
Input power is supplied at the B+ terminal. Minimum input
voltage is 6.8 volts and maximum is 13.2 volts. The upper limit
is based upon power dissipation in the LM3914 assuming all
10 LED’s are lit and ambient temperature is 25
°
C. The board
will survive input transients up to 25 volts provided that
average power dissipation in the LM3914 does not exceed 1.3
watts.
OUT:
An analog output is supplied at the OUT terminal. The signal
it provides is nominally 0.5 volts at zero pressure and 4.5 volts
at full scale. Zero pressure voltage is adjustable and set with
R11. This output is designed to be directly connected to a
microcomputer A/D channel, such as one of the E ports on an
MC68HC11.
GND:
There are two ground connections. The ground terminal on
the left side of the board is intended for use as the power
supply return. On the right side of the board one of the test
point terminals is also connected to ground. It provides a
convenient place to connect instrumentation grounds.
TP1:
Test point 1 is connected to the LM3914’s full scale
reference voltage which sets the trip point for the uppermost
LED segment. This voltage is adjusted via R1 to set full scale
pressure.
TP2:
Test point 2 is connected to the +5.0 volt regulator output.
It can be used to verify that supply voltage is within its 4.75 to
5.25 volt tolerance.
P1, P2:
Pressure and Vacuum ports P1 and P2 protrude from the
sensor on the right side of the board. Pressure port P1 is on
the top and vacuum port P2 is on the bottom. Neither port is
labeled. Maximum safe pressure is 700 kPa.
F
Freescale Semiconductor, Inc.
n
.