Vaisala Barocap PMB100 User manual

USER'S GUIDE
Vaisala BAROCAP® Baromete
r
Module
PMB100
M010035EN-A

PUBLISHED BY
Vaisala Oyj Phone (int.): [phone]
P.O. Box 26 Fax: [phone]
FIN-00421 Helsinki
Finland
Visit our Internet pages at http://www.vaisala.com/
© Vaisala 2006
No part of this manual may be reproduced in any form or by any means, electronic or
mechanical (including photocopying), nor may its contents be communicated to a third
party without prior written permission of the copyright holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding obligations for
Vaisala towards the customer or end user. All legally binding commitments and
agreements are included exclusively in the applicable supply contract or Conditions of
Sale.

CHAPTER 1_______________________________________________________ GENERAL INFORMATION
VAISALA __________________________________________________________________________ 3
Table of contents
CHAPTER 1
GENERAL INFORMATION ............................................................................4
Safety.........................................................................................4
Warranty ....................................................................................4
CHAPTER 2
PRODUCT DESCRIPTION.............................................................................5
BAROCAP®pressure sensor..................................................5
CHAPTER 3
OPERATION...................................................................................................7
Connections..............................................................................7
Dimensions in mm (in inches).................................................9
Pressure calculations...............................................................9
Offset/Gain corrections..........................................................10
CHAPTER 4
TECHNICAL DATA.......................................................................................11
Specifications .........................................................................11
Operating range..............................................................11
Accuracy.........................................................................11
General...........................................................................11
APPENDIX A
READING COEFFICIENTS FROM THE EEPROM......................................13

USER'S GUIDE_______________________________________________________________________
4 ____________________________________________________________________ M010035EN-A
CHAPTER 1
GENERAL INFORMATION
Safety
Throughout the manual, important safety considerations are
highlighted as follows:
WARNING Warning denotes a serious hazard. It calls attention to a procedure,
practice, condition or the like, which, if not correctly performed or
adhered to, could result in injury to or death of personnel.
CAUTION Caution denotes a hazard. It calls attention to a procedure, practice,
condition or the like, which, if not correctly performed or adhered to,
could result in damage to or destruction of part or all of the product.
NOTE Note highlights important information. It calls attention to an
essential procedure, practice, condition or the like.
Warranty
Vaisala issues a guarantee for the material and workmanship of this
product under normal operating conditions for one (1) year from the
date of delivery. Exceptional operating conditions, damage due to
careless handling and misapplication will void the guarantee.

CHAPTER 2_______________________________________________________ PRODUCT DESCRIPTION
VAISALA __________________________________________________________________________ 5
CHAPTER 2
PRODUCT DESCRIPTION
The PMB100 for OEM applications is a new circuit board mountable
barometric pressure transducer that is designed to interface with an
AD converter and a microprocessor.
The PMB100 module is characterized over 800 to 1100 hPa (mbar)
pressure range and over –5 to +45C temperature range. It ouputs
pressure dependant voltage within 0 and 2.5 VDC along with a
reference voltage of 2.5 VDC. All pressure and temperature related
coefficients are given in a module specific certificate and also stored
in an incorporated EEPROM, which uses the I2C interface. All the user
needs to do is to measure the temperature of the module and the two
voltage outputs and then calculate the compensated pressure reading
using the coefficients. A final offset correction against a high-class
pressure standard is recommended as a final touch.
BAROCAP®pressure sensor
The PMB100 barometer modules use the BAROCAP® silicon
capacitive absolute pressure sensor. The BAROCAP®sensor has
excellent hysteresis and repeatability characteristics, low temperature
dependence and a very good long-term stability. The ruggedness of
the BAROCAP®sensor is outstanding and the sensor is resistant to
mechanical and thermal shocks.
Thin film metallization Silicon
Vacuum gap Silicon
Glass
Silicon diaphragm
Figure 1 The BAROCAP® pressure sensor
The BAROCAP® pressure sensor consists of two layers of single
crystal silicon having a layer of glass between them. The thinner
silicon layer is etched on both sides to create an integrated vacuum

USER'S GUIDE_______________________________________________________________________
6 ____________________________________________________________________ M010035EN-A
reference chamber for the absolute pressure sensor and to form a
pressure sensitive silicon diaphragm. The thicker silicon layer is the
rigid base plate of the sensor and it is clad with a glass dielectric. The
thinner piece of silicon is electrostatically bonded to the glass surface
to form a strong and hermetic bond. Thin film metallization has been
deposited to form a capacitor electrode inside the vacuum reference
chamber; the other electrode is the pressure sensitive silicon
diaphragm.
The coefficients of thermal expansion of silicon and glass materials
used in the BAROCAP® pressure sensor are carefully matched
together in order to minimize the temperature dependence and to
maximize the long-term stability. The BAROCAP® pressure sensor is
designed to achieve zero temperature dependence at 1000 hPa and its
long-term stability has been maximized by thermal ageing at an
elevated temperature.
The BAROCAP® capacitive pressure sensor features a wide dynamic
range and no self-heating effect. The excellent hysteresis and
repeatability characteristics are based on the ideal spring
characteristics of single crystal silicon. In the BAROCAP®pressure
sensor, the silicon material is exerted to only few percent of its whole
elastic range.

CHAPTER 3________________________________________________________________ OPERATION
VAISALA __________________________________________________________________________ 7
CHAPTER 3
OPERATION
Connections
The pin assignments of the PMB100 module are according to Figure
2. Connect 8...16 VDC supply voltage (typically 2 mA) to the pin VDC
and the ground plane directly to the pin GND. The output signal (0...2.5
VDC) is measured from the pin OUT and the reference signal (2.5 VDC
± 2%) from the pin REF.
If the coefficients are read from the EEPROM, the pin +5 V, SCL and
SDA are also connected. The +5 V-pin is used for supply voltage of the
EEPROM. The pins SCL and SDA are for data transfer between the
EEPROM and a microprocessor.
Temperature of the module is measured with an external T sensor,
which should be placed as close to the module as possible.
The module can also be switched to shut down mode by using a TTL
level trigger on the pin SH. A signal 0.7 V or lower activates and a
signal higher than 2 V switches the module off.
Out
VDC
GND
+ 5V
SCL
SDA
REF
SH
Figure 2 Pin assignments

USER'S GUIDE_______________________________________________________________________
8 ____________________________________________________________________ M010035EN-A
In applications where adverse electromagnetic fields exist, an
additional EMI protection may be necessary. In Figure 3, there is an
example of an electromagnetic interference protection of the PMB100
module. The EMI filters should be placed as close to the pins as
possible.
Power
regulator
+
-
Vout
filter
filter
filter
GND
Vref
PMB100 module
Copper pour connected to ground.
GND directly connected
to ground plane
OUT
VDC
REF
Vout
Vref
VDC
GND
Figure 3 Electromagnetic interference protection of the
PMB100. Filters, for example, T-type EMI
suppression filters with capacitance of 47pF (like
Murata, DSS310-55Y5S470M100). This connection
setup fulfills the RF field immunity standard
EN61000-4-3.

CHAPTER 3________________________________________________________________ OPERATION
VAISALA __________________________________________________________________________ 9
Dimensions in mm (in inches)
Pressure calculations
Measure the following parameters of the PMB100 barometer module:
- output voltage Vout
- reference voltage Vref
- module temperature Tm (°C)
NOTE External T-sensor is required for temperature compensation purpose
with minimum ±1°C accuracy.
1°C error in temperature measurement causes 0.14 hPa error in
pressure value.

USER'S GUIDE_______________________________________________________________________
10 ___________________________________________________________________ M010035EN-A
In pressure calculation, normalized voltage (Vn) and temperature (Tn)
are required. The normalization of the parameters is performed by
using the equations 1 and 2.
[] 1...1,12 −∈−
ö
ç
è
æ⋅= n
ref
out
nV
V
V
V(1)
[] 1...1,
128 0−∈−= n
m
nTT
T
T(2)
Constant T0is found in the list of coefficient or in the EEPROM.
Normalized pressure Pnis calculated according to the equation 3. All
the module specific coefficients are available in the list of coefficients
supplied with each module or in the EEPROM.
[] 1...1,
3
31
2
21
2
1211
2
0201
3
30
2
201000
−∈
ù
ê
ê
ê
ê
ë
é
⋅⋅+⋅⋅+⋅⋅+⋅⋅+
⋅+⋅+
⋅+⋅+⋅+
⋅= n
nnnnnnnn
nn
nnn
nP
TVaTVaTVaTVa
TaTa
VaVaVaa
kP
(3)
Compensated pressure Pis then calculated by using the equation 4.
950150 +⋅= n PP hPa (4)
Offset/Gain corrections
A final offset/gain correction against a high-class pressure standard is
recommended as a final touch. The offset and gain adjustments are
done after the pressure calculation by the user's host system.