www.sensirion.com Version 2 – February 2013
1/7
SDP1108/SDP2108
Low Differential Pressure Sensor
with fast response time
− For medical ventilators (ICU and home care)
− High sensitivity below 10 Pa to measure small volume flow (neonatal)
− Fast response time for efficient trigger function
− Unsurpassed performance thanks to CMOSens
®
technology
− Offset and hysteresis free
− Fully calibrated and temperature compensated
− Not sensitive to the mounting orientation and vibrations
SDPx108 Product Summary
The SDPx108 sensor family is a differential pressure
sensor for air based on the successful SDP1000/
SDP2000 sensor from Sensirion AG. The response time
of the SDPx108 has been optimized for medical
ventilation applications.
Mounted in a rugged, chemically inert PPS housing the
SDPx108 differential pressure sensors feature a unique
dynamic range, zero offset and unsurpassed long term
stability. This makes it an ideal fit for demanding yet cost
sensitive OEM applications in medical and HVAC
equipment.
The SDPx108 is fully RoHS compliant.
The SDPx108 is supplied with 5.0 V and provides a
0.25…4.0 V output. Although the output of the sensor is
analog, the internal linearization and temperature
compensation is performed digitally. This results in a
superior accuracy, outstanding resolution (up to 0.05 Pa),
and lowest temperature dependence.
Its leading performance is based on Sensirion’s proprietary
CMOSens
®
sensor technology which combines the sensor
element with amplification and A/D conversion on one
single silicon chip. The differential pressure is measured by
a thermal sensing element. In contrast to other thermal
differential pressure sensors only a very small amount of
air is required. This leads to a reliable operation even
under harsh conditions. In comparison to membrane and
piezo-resistive based sensors the SDPx108 differential
pressure sensors show an extended measurement range,
better offset stability and improved reproducibility even at
lowest pressure ranges. In addition the SDPx108 is robust
against pressure bursts and shows no sensitivity to the
mounting orientation.
Applications
Medical applications:
• Homecare ventilation
• Intensive care ventilation (ICU)
• Other
Block Diagram
Differential
pressure
Sensor
CMOSens
®
SENSOR CHIP
DIGITAL
Linearization and
Temperature
compensation
A/D converter
Memory
D/A
converter
Pin 1:
V
DD
5.0 V
Pin 3: OUT
0.25 V to 4 V
Pin 2:
GND
www.sensirion.com Version 2- February 2013 2/7
1 Sensor Output Characteristics
1
SDPx108-R
0.25
0.75
1.25
1.75
2.25
2.75
3.25
3.75
0 20 40 60 80 100
differential pressure [% FS]
output voltage [V]
The SDPx108-R provides a fully calibrated voltage
output. To enhance resolution and accuracy at very
low differential pressures, the SDPx108 standard
version (SDPx108-R) comes with a root-square
output characteristics.
For high-quantity OEM applications, other ranges
and output characteristics can be realized. E.g.
linear output and a bidirectional measurement
range is possible. Please contact Sensirion for
further information.
[ ]
PaFS
VVVoltageOutput
Pa ⋅
−
=
2
75.3 25.0_
][Press. Diff.
Use this formula to convert the sensor output into
physical value.
1
Calibration conditions apply unless otherwise noted: 23°C and p
absolute
= 966 mbar, dry air, V
DD
= 5.000 V. FS is 500Pa for the SDP1108 and
3500 Pa for the SDP2108.
2 Specifications
Table 1: SDPx108-R Sensor specifications
1
Parameter SDP1108-R SDP2108-R Unit
Min Typ Max Min Typ Max
Measurement range
0.25 - 4 0.25 4 Volts
0 - 500 0 3500 Pa
0 - 2 0 14 Inch water
Accuracy
3
20% FS to 100% FS - 1.0 2.0 - 1 2 % Measured Value
4
0 to 20% FS - 0.2 0.4 - 0.2 0.4 % Full Span
5
zero
2
-
15
0.01
40
0.06 -
20
0.1
50
0.6
mV
Pa
Repeatability 100 to 500 Pa - 0.3 1.0 - 0.3 1.0 % Measured Value
0 to 100 Pa - 0.05 0.2 - 0.06 0.2 % Full Span
5
Null drift per year
6
- 0 0.1 - 0 0.3 Pa / year
Additional error over
temperature
7
(T ≠ 23°C)
0 to 100 % FS - 0.03 0.05 - 0.03 0.05 % Measured Value
4
/ °C
zero - 1 2 - 1 3 mV/°C
Response time
(8)
6.6 8.0 10.1 6.6 8.0 10.1 ms
Cut off frequency of internal filter 17 20 24 17 20 24 Hz
1
Calibration conditions apply unless otherwise noted: 23°C and p
absolute
= 966 mbar, dry air, V
DD
= 5.000 V
2
Variance between the zero point (offset) of different sensors measured under the same conditions (e.g. same supply voltage, temperature, …)
3
Include deviations due to linearity, hysteresis, and repeatability
4
% Measured value = (SDPx108 output [Pa] - output of reference instrument [Pa]) / output of reference instrument [Pa].
5
Full span is defined as 3750 mV / 500 Pa for SDP1108 and 3750 mV / 3500 Pa for the SDP2108.
6
Drift over time due to aging, pressure cycles… Test results can be provided.
7
The additional error due to temperature variation is temporary. Once the sensor is back to the calibration temperature, the shift disappears
(no hysteresis).
8
Tau= 0 to 63%, filter response time = 8ms. For faster response time, contact Sensirion.
www.sensirion.com Version 2 – February 2013 3/7
Table 2: Additional sensor specifications.
Parameter
Media Calibration
1
Air, N
2
– for other gases contact Sensirion AG.
Media Compatibility Air, N
2
, O
2
Operating Conditions
2
:
- Temperature
- Humidity
-10 °C … +60 °C / 14°F … 140 °F
non-condensing
Ambient storage conditions
3
-40 °C … +80 °C / -40°F … 176 °F
Orientation sensitivity below zero point accuracy
Admissible overpressure (short term) 1 bar (14.5 PSI)
Burst Pressure Capability 2 bar (29 PSI)
Weight 14 g
Protection Class IP 20
Wetted materials Glass (silicon nitride, silicon oxide), Silicon, PPS (Polyphenylene Sulfide),
PEEK (Polyetheretherketone), FR4, Silicone as static sealing, Epoxy, Gold
Electromagnetic compatibility EN 61000-4-2 Air discharge (ESD) ± 2 kV
Lead free ROHS compliant.
1
Sensors are calibrated for a specific gas, please contact Sensirion when you employ different gases than the specified.
2Condensation of liquids or dust on the sensor membrane might lead to sensor offset. Please consult our application notes on www.sensirion.com.
3For maximum 2 weeks
2.1 Temperature Compensation
The SDPx108 differential pressure sensors feature a
sophisticated built-in temperature compensation circuit.
The temperature is measured on the CMOSens
®
chip by
means of a PTAT bandgap reference temperature
sensor. Its data is fed into a compensation circuit which
is also integrated on the CMOSens
®
sensor chip. No
external temperature compensation is therefore required.
2.2 Altitude Correction
The SDPx108 differential pressure transducers achieve
their unsurpassed performance by using a dynamic
measurement principle: An applied differential pressure
forces a small air flow through the SDPx108, which
measures this air flow.
The sensor signal is dependant on the ambient air
density. The temperature effect on density is
compensated by internal intelligence (see Paragraph
2.3). Effects on density due to a change of ambient
pressure, typically a change of altitude above sea level,
can be compensated using a correction factor according
to the following equation:
Dp
eff
= Dp
sensor
*
P
cal
/ P
amb
Where Dp
eff
is the effective differential pressure, Dp
sensor
the differential pressure indicated by the SDPx108, P
cal
the absolute pressure during calibration (966 mbar) and
P
amb
the actual ambient absolute pressure.
This leads to the following correction factors:
Table 3: Altitude correction factors.
Altitude
[meter]
Ambient Pressure
(P
amb
) [mbar]
Correction Factor
P
cal
/ P
amb
0
1013
0.95
250
984
0.98
425
966
1.00
500
958
1.01
750
925
1.04
1500
842
1.15
2250
766
1.26
3000
697
1.38
Example:
The SDP1108 is used at 750 m above sea level. The
output of the SDP1108 shows 0.5 V, which
corresponds to Dp
sensor
= 33.3 Pa. Taking into account
the correction factor P
cal
/ P
amb
= 1.04 the effective
differential pressure Dp
eff
is 33.3 Pa * 1.04 = 34.6 Pa.
Note:
In many medical and HVAC applications such as filter
monitoring, fan/ventilator control or air flow
measurement the described effect is actually
welcome since at the end the mass flow and not
volume flow is the effective value to control.
www.sensirion.com Version 2 – February 2013 4/7
3 Physical Dimensions and Mounting Information
3.1 Housing
The SDPx108 differential pressure transducers are
mounted in chemically inert PPS housing. The rugged
package has been designed to withstand continuous
overpressures of at least 1 bar (14.5 PSI). Burst pressure
is > 2 bar (29 PSI)
The physical dimensions and mounting information is
given in Figure 1 and 2.
3.4
(0.134)
5.4
(0.213)
2.54
(0.100)
16.0
(0.630)
44.0
(1.732)
SDP100000206-10033-250-001
Hi Lo
1.8
(0.071)
30.0
(1.181)
Pin# 1 2 3
A
G C
F
D
E
H
I
No Components
inside this Area
B
B
A
Figure
1
:
Pin out and physical dimensions in mm (inch). The
drawing is not to scale.
Figure
2
:
SDPx
108 PCB footprint. The drawing is not
to scale.
3.2 Soldering Instructions
The SDPx108 differential pressure sensors can be
wave soldered. Direct reflow soldering is not
recommended since it may affect the accuracy.
If reflow soldering is required Sensirion recommends to
use an SMD connector (e.g. type Samtec SSM-103-L-
SV) and to mount the SDPx108 after soldering.
22.1
(0.870)
Dim.
[mm]
[inch]
[mi
l]
A 3.00 0.118 118
B 3.30 0.130 130
C 1.20 0.047 47
D 10.20 0.402 402
E 28.20 1.110 1110
F 2.54 0.100 100
G 0.60 0.024 24
H 0.50 0.020 20
I 22.70 0.894 894
Pin#
Function
1
VDD (5
Vdc)
2 Ground
3 OUT (0.25…4
Vdc)
18.3
(0.720)
30.5
(1.200)
5.2
(0.205)
13.1
(0.516)
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3.3 Connecting Hose
Sensirion recommends a hose with an inner diameter
of 3.18 to 3.8mm (1/8 to 3/20 inch). Due to the dynamic
measurement principle, a small air flow is required
(Figure 3) which leads to a dependence on the length
of the hose (Table 4). Tubes up to 1 m show less than
2 % error of the measured value (Table 4).
Figure 3: Typical air flow through the SDP1108. Please note:
1 scc/min = 1 cm3/min at 0°C and 1013 mbar pressure
(1 sccm = 0.001 norm liter).
Table 4: Influence of the length of the connecting hose
on
the accuracy (using 4 mm inner diameter).
Deviation is
given in % of the measured value. Example SDP1108
: a
500 Pa difference pressure is shown as 492.5 Pa when
using 1 m tube with 4 mm inner diameter.
Table 5: Maximum flow through the sensor element.
Mass flow through sensor element:
SDP1108-R SDP2108-R
123 sccm (@ 500 Pa) 66 sccm (@3500 Pa)
4 Electrical Specifications
4.1 Power Supply
The SDPx108 differential pressure sensors require a
stable voltage supply of 5.0 V. The requirements for the
electrical supply are specified in Table 5.
4.2 Voltage Output
The SDP1108 features a voltage output from 0.25 V to
4.0 V. An output voltage below 0.25 V indicates a
negative differential pressure (not calibrated).
The resistive load at the output pin should be larger
than 20 kOhm. The capacitive load at the output pin
must not be larger than 200 pF. If the design shows a
larger capacity at the output pin an additional resistor is
required in series at the output (e.g. 620 Ohm).
Table 6: SDPx108 electrical characteristics.
Parameter Conditions Min. Typ. Max. Units
Power Supply Voltage V
DD
4.75 5.0 5.25 VDC
Operating Current 5 V, no load, zero flow 5.1 6 mA
Output capacitive load C
load
20 200 pF
Recommended load R
load
20 100 ∞ kΩ
Hose length SDP1108 SDP2108
@FS @0.5 FS @FS @0.5FS
0.5 m (20 inch) -0.75% -0.95% -0.06% -0.07%
1.0 m (40 inch) -1.5% -1.9% -0.12% -0.14%
2.0 m (80 inch) -3.0% -3.8% -0.24% -0.28%
www.sensirion.com Version 2 – February 2013 6/7
5 Ordering Information
When ordering please refer to the following part names and article numbers. For the latest product information and
local distributor check out Sensirion’s website on http://www.sensirion.com
Part Name Article Number
SDP1108-R 1-100339-03
SDP2108-R 1-100729-03
Revision history
Date
Revision
Author
Changes
October 2008
V1.0
PHA
Initial release
June
2
010
V1.1
DAT
SDP2108 launched,
New Item Number (see product change notification PCN
081015), block diagram (page 1), minor changes
February 2013
V2
ANB
Updated product number.
Minor layout updates.
www.sensirion.com Version 2 – February 2013 7/7
Important Notices
Warning, personal injury
Do not use this product as safety or emergency stop devices or in any
other application where failure of the product could result in personal
injury (including death). Do not use this product for applications other
than its intended and authorized use. Before installing, handling,
using or servicing this product, please consult the data sheet and
application notes. Failure to comply with these instructions could
result in death or serious injury.
If the Buyer shall purchase or use SENSIRION products for any unintended
or unauthorized application, Buyer shall defend, indemnify and hold
harmless SENSIRION and its officers, employees, subsidiaries, affiliates
and distributors against all claims, costs, damages and expenses, and
reasonable attorney fees arising out of, directly or indirectly, any claim of
personal injury or death associated with such unintended or unauthorized
use, even if SENSIRION shall be allegedly negligent with respect to the
design or the manufacture of the product.
ESD Precautions
The inherent design of this component causes it to be sensitive to
electrostatic discharge (ESD). To prevent ESD-induced damage and/or
degradation, take customary and statutory ESD precautions when handling
this product.
See application note “ESD, Latchup and EMC” for more information.
Warranty
SENSIRION warrants solely to the original purchaser of this product for a
period of 12 months (one year) from the date of delivery that this product
shall be of the quality, material and workmanship defined in SENSIRION’s
published specifications of the product. Within such period, if proven to be
defective, SENSIRION shall repair and/or replace this product, in
SENSIRION’s discretion, free of charge to the Buyer, provided that:
• notice in writing describing the defects shall be given to SENSIRION
within fourteen (14) days after their appearance;
• such defects shall be found, to SENSIRION’s reasonable satisfaction,
to have arisen from SENSIRION’s faulty design, material, or
workmanship;
• the defective product shall be returned to SENSIRION’s factory at the
Buyer’s expense; and
• the warranty period for any repaired or replaced product shall be limited
to the unexpired portion of the original period.
This warranty does not apply to any equipment which has not been
installed and used within the specifications recommended by SENSIRION
for the intended and proper use of the equipment. EXCEPT FOR THE
WARRANTIES EXPRESSLY SET FORTH HEREIN, SENSIRION MAKES
NO WARRANTIES, EITHER EXPRESS OR IMPLIED, WITH RESPECT TO
THE PRODUCT. ANY AND ALL WARRANTIES, INCLUDING WITHOUT
LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR
A PARTICULAR PURPOSE, ARE EXPRESSLY EXCLUDED AND
DECLINED.
SENSIRION is only liable for defects of this product arising under the
conditions of operation provided for in the data sheet and proper use of the
goods. SENSIRION explicitly disclaims all warranties, express or implied,
for any period during which the goods are operated or stored not in
accordance with the technical specifications.
SENSIRION does not assume any liability arising out of any application or
use of any product or circuit and specifically disclaims any and all liability,
including without limitation consequential or incidental damages. All
operating parameters, including without limitation recommended
parameters, must be validated for each customer’s applications by
customer’s technical experts. Recommended parameters can and do vary
in different applications.
SENSIRION reserves the right, without further notice, (i) to change the
product specifications and/or the information in this document and (ii) to
improve reliability, functions and design of this product.
Copyright
©
2001-2013, SENSIRION.
CMOSens
®
is a trademark of Sensirion
All rights reserved
RoHS and WEEE Statement
The SDPx108 Series complies with requirements of the following
directives:
• EU Directive 2002/96/EC on waste electrical and electronic
equipment (WEEE), OJ13.02.2003; esp. its Article 6 (1) with
Annex II.
• EU Directive 2002/95/EC on the restriction of the use of certain
hazardous substances in electricaland electronic equipment
(RoHS), OJ 13.02.2003; esp. its Article 4.
Headquarters and Subsidiaries
SENSI
RION AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland
phone: +41 44 306 40 00
fax: +41 44 306 40 30
info@sensirion.com
www.sensirion.com
Sensirion Inc., USA
phone: +1 805 409 4900
info_us@sensirion.com
www.sensirion.com
Sensirion Japan Co. Ltd.
phone: +81 3 3444 4940
info@sensirion.co.jp
www.sensirion.co.jp
Sensirion Korea Co. Ltd.
phone: +82 31 345 0031 3
info@sensirion.co.kr
www.sensirion.co.kr
Sensirion China Co. Ltd.
phone: +86 755 8252 1501
info@sensirion.com.cn
www.sensirion.com.cn
Sensirion AG (Germany)
phone: +41 44 927 11 66
info@sensirion.com
www.sensirion.com To find your local representative, please visit www.sensirion.com/contact
