KISTERS HyQuest Solutions VHPS SDI-12 User manual

Vented Hydrostatic Pressure Sensor
(VHPS): User’s Manual
HyQuest Solutions
-KISTERS Group-
06 JUNE 2020

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Revision Sheet
Release No.
Date
Revision Description
1.0
23 June 2020
First Release

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Content
1SAFETY INSTRUCTIONS .............................................................................................6
2INTRODUCTION ........................................................................................................7
3TECHNICAL DATA......................................................................................................7
4SDI-12 DATA TRANSFER INTERFACE...........................................................................8
4.1 Description ......................................................................................................................... 8
4.2 SDI-12 Command Set........................................................................................................... 8
4.2.1 Data Logger/Controller Commands and Sensor Responses..........................................................8
4.2.1.1 Break..............................................................................................................................................9
4.2.1.2 Acknowledge Active.......................................................................................................................9
4.2.1.3 Change Address Command............................................................................................................9
4.2.1.4 Address Query Command (?!)......................................................................................................10
4.2.1.5 Start Measurement Command ....................................................................................................10
4.2.1.6 Extended Measurements Command ...........................................................................................11
4.2.1.7 Service Request (from sensor to data logger) .............................................................................12
4.2.1.8 Start Concurrent Measurement Command.................................................................................12
4.2.1.9 Start Verification Command ........................................................................................................12
4.2.1.10 Additional Concurrent Measurements Command.......................................................................13
4.2.1.11 Continuous Measurement Command .........................................................................................13
4.2.2 CRC-16 Checksum ........................................................................................................................14
4.2.3 SDI-12 extended commands........................................................................................................14
4.2.3.1 Setting pressure unit....................................................................................................................14
4.2.3.2 Reading pressure unit..................................................................................................................15
4.2.3.3 Setting recalibration value of zero-point pressure......................................................................15
4.2.3.4 Reading recalibration value of zero-point pressure ....................................................................15
4.2.3.5 Setting recalibration value of nominal pressure..........................................................................16
4.2.3.6 Reading recalibration value of nominal pressure........................................................................16
4.2.3.7 Setting temperature unit.............................................................................................................16
4.2.3.8 Reading temperature unit ...........................................................................................................17
4.2.3.9 Setting user identification string..................................................................................................17
4.2.3.10 Reading user identification string................................................................................................18

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4.2.3.11 Saving settings in flash memory ..................................................................................................18
5RECALIBRATION...................................................................................................... 18
5.1 Zero-point pressure recalibration ...................................................................................... 18
5.2 Nominal pressure recalibration ......................................................................................... 19
5.3 Zero-point and nominal pressure recalibration .................................................................. 20
6UNIT CONVERSION .................................................................................................21
7CONTACT DATA ......................................................................................................22
7.1 Australia........................................................................................................................... 22
7.2 New Zealand..................................................................................................................... 22
7.3 Europe.............................................................................................................................. 22
7.4 Latin America.................................................................................................................... 22
7.5 North America .................................................................................................................. 22

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Glossary
ACRONYM
Description
A
SI unit symbol for “Ampere”, physical unit for electrical current
ASCII
American Standard Code for Information Interchange
DB
Data Byte
DW
Data Word
mm
SI unit symbol for “millimetre”, metrical system
P
Pressure
PN
Nominal pressure
PZP
Zero-point pressure
SI
International System of Units
T
Temperature
PN
End of temperature range
PZP
Start of temperature range
SDI-12
A Serial-Digital Interface Standard for Microprocessor-Based Sensors as described in the SDI-12 specifications
http://www.sdi-12.org
VDC
Direct Current
W
SI unit symbol for “Watt”, physical unit of power
ZP
Zero Point
@
at

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1Safety Instructions
•Read the user manual including all operating instructions prior to installing, connecting and pow-
ering up the HyQuest Solutions VHPS. The manual provides information on how to operate the
sensor system. The manual is intended to be used by qualified personnel, i.e. personnel that has
been adequately trained, is sufficiently familiar with installation, mounting, wiring, powering up
and operation of radar sensors.
•Keep the user manual at hand for later reference!
•If you encounter problems understanding the information in the manual (or part thereof), please
consult the manufacturer or its appointed re-seller for further support.
•The manual provides information on how to operate the sensor system.
•Do not use the HyQuest Solutions VHPS in areas where there is a danger of explosion.
•The present user manual specifies environmental/climatic operating conditions as well as me-
chanical and electrical conditions. Installation, wiring, powering up and operation the HyQuest
Solutions VHPS must strictly comply with these specifications.
•Never make any electrical or mechanical diagnostics, inspections or repairs under any circum-
stances. Return the sensor to the manufacturers named repair centre. You can find information
on how to return items for repair in the relevant section of the HyQuest Solutions web site.
•Disposal instructions: After taking the HyQuest Solutions VHPS out of service, it must be disposed
of in compliance with local waste and environmental regulations. The HyQuest Solutions VHPS is
never to be disposed in household waste!

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2Introduction
Thank you for opting for HyQuest Solutions’Vented Hydrostatic Pressure Sensor (VHPS)!
The VHPS SDI-12 provides the following functions:
•Zero-point and nominal pressure recalibration
•SDI-12 interface
•Pressure units selectable
•Temperature units selectable
•Additional identification string
Vented Hydrostatic Pressure Sensors are typically used to measure water levels in running or standing
water bodies. The integration with a data logger –for instance a data logger of the HyQuest Solutions iRIS
family of data loggers –is easy thanks to the sensor’s SDI-12 interface (Version 1.3).
The VHPS measures both water pressure and water temperature. The readings are available via SDI-12
commands. The water temperature is also internally used to provide for a temperature compensated
pressure reading. The VHPS is a vented sensor ensuring natural barometric pressure compensation.
Depending on the actual deployment of the sensor, VHPS can be ordered with either stainless steel or
titanium housing. Likewise, a choice of PUR, PE (for drinking water) and TFE (Teflon impregnated for con-
taminated waters) cables is available.
The present manual describes the common features of all VHPS sensors.
3Technical Data
Table 1 provides an overview on the major specifications of the VHPS Vented Hydrostatic Pressure Sensor.
Table 1. VHPS Specifications
Parameter
MIN
TYP
MAX
Unit
Communication interface: SDI-12
1200
V1.3
1200
bps
Power supply voltage
8.0
12.0
30.0
V DC
Max Current
< 0.5
< 6
mA
Operational Temperature Range
-5
+80
°C
Pressure Measurement range
5
20
10
250
mH2O
mH2O
Pressure Resolution
0.01
% FS
Pressure Measurement Accuracy
≤ ± 0.1
± % FS
Temperature Measurement Range
-25
+85
°C
Temperature Resolution
0.05
°CS
Accuracy Temperature Measurement
≤ ± 0.3
≤ ± 0.5
°C
Pressure Resolution
0.01
% FS
Ingress Protection Rating
IP68
---
Mechanical
Ø24 x H157
Ø0.95 x H6.18
mm
inch

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4SDI-12 Data Transfer Interface
Table 2 –SDI-12 Interface Specs
Protocol
SDI-12, Version 1.3
Default Address
0 (factory settings)
Transfer Rate
1200 baud
Start Bits
1
Data bits
7
Parity
1 bit, even
Stop Bit
1
4.1 Description
SDI-12 is a standard for interfacing data recorders with microprocessor-based sensors. SDI-12 stands for
serial/digital interface at 1200 baud. SDI-12 is intended for applications with the following requirements:
•Battery powered operation with minimal current drain, max. 420mA@12V
•Bus operation: use of a single data recorder with multiple sensors on one cable; each of these
devices must be identified with a unique address, which is represented by a single ASCII char-
acter; if several units connected through the same physical SDI-12 bus must have a distinct
address
•Power is supplied to the sensors through the physical wires of the SDI-12 interface
Figure 1 –SDI-12 Bus (source: http://www.sdi-12.org/current_specification/SDI-12_version-1_4-Jan-10-2019.pdf)
4.2 SDI-12 Command Set
The SDI-12 command implementation is compliant with SDI-12 Specification 1.3.
4.2.1 Data Logger/Controller Commands and Sensor Responses
The following sections describe the basic commands and extended SDI-12 commands implemented in
VHPS sensors. For each command, and where appropriate, the responses provided by the sensor is de-
scribed. SDI-12 is a bi-directional communication protocol. Typically, sensors act as clients providing an-
swers to commands received from a data acquisition device. A data logger or controller sends commands
to the sensor.
SDI-12 commands send by a data-acquisition device or intelligent controller use the same base structure:

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•the sensor address –denoted ‘a’ with a value range [0 …9, A …Z, a …z]
•the character "!" terminates the command
•most commands have a command character
Caution: The address character "?" can only be used if only a single sensor is connected to the physical
SDI-12 bus. All sensors on the bus will respond to the “?” address character.
All responses sent after a command has been received and processed use the same base structure:
•the address, and
•the character chain “<CR><LF>” to terminate the answer.
•most responses also contain data with or without a CRC-16.
4.2.1.1 Break
A break is sent to wake up the sensor(s). Sending a break command ensures that all sensors on the bus
will wake up and prepare to be ready to not miss the commands that follow. A break is a constant bus
level (spacing) for 12 ms.
4.2.1.2 Acknowledge Active
This command ensures that the addressed sensor responds to the data logger. This command has no
command character.
•Command: a!
•Response: a<CR><LF>
With a == the sensor address (0, 1..9, A..Z, a..z)
4.2.1.3 Change Address Command
Change/set the address of a connected sensor. The factory default address of each sensor is "0".
Caution: To avoid addressing conflicts on the bus, each sensor must have its unique address on the bus.
Preferably, the unique address is different from the default address. If two or more sensors on the same
bus share the same address, address conflicts will arise making the bi-directional SDI-12 communication
impossible.
•Command: aAb!
•Response: b<CR><LF>
where:
•a old sensor address (0, 1..9, A..Z, a..z)
•b new sensor address (0, 1..9, A..Z, a..z)
Example Change Address Command (aI!)
Changing the Address from “0”to “1”
•Command: 0A1!
•Response: 1<CR><LF>
Changing the Address from “1”to “0”
•Command: 1A0!

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•Response: 0<CR><LF>
4.2.1.4 Address Query Command (?!)
This command queries the sensor address. Using the generic ‘?’ address, forces all sensors connected to
the bus to respond. It must be noted that if more than a single sensor is connected to the bus, they will
all respond, causing a bus contention. However, to comply with the SDI-12 standard, each sensor is re-
quired to support the wild card address character (?) with the acknowledge active command (?!).
•Command: ?!
•Response: a<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
4.2.1.5 Start Measurement Command
To keep power consumption low, SDI-12 sensors hibernate between measurements. The Start Measure-
ment command wakes up the sensor and tells it to take a measurement. The VHPS will start measuring
both pressure and temperature. In compliance with the SDI-12 standard, the sensor responds providing
two bits of information:
•the number of measurements ‘n’ in the valid range 1 to 9 (in the case of the VHPS, n=2), and
•the time ‘ttt’ until these two measurements will be ready.
Note that SDI-12 sensors will not provide the actual measurement unless they receive send data command
(D0!). If the sensor has the measuring results available before the specified time expires, then it sends a
Service Request (see 4.2.1.7) to the data logger.
•Command: aM! Requesting measured values without CRC-16 checksum
aMC! Requesting measured values with CRC-16 checksum
•Response: atttn<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•ttt == time in seconds until measurements/readings are available
•n == no. of measured data (0..9)
n = 2 (One pressure and one temperature measured value in the case of the VHPS)
After the M command and before the sensor issues the service request, the data recorder may not com-
municate with any other sensor. The sensor must not drive the data line until it sends a service request.
The recorder must not drive the data line while waiting for the service request.
Examples Get Measurement
•Command: 0M! (start measurement)
•Response: 00012<CR><LF> (2 measurements ready in 1 second)
•Response: 0<CR><LF> (Service Request)
•Command: 0D0! (send data)
•Response: 0+0.012-1.3<CR><LF> (e.g. +0.012bar, -1.3°C)

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•Command: 0M1! (start measurement)
•Response: 00011<CR><LF> (2 measurements ready in 1 second)
•Response: 0<CR><LF> (Service Request)
•Command: 0D0! (send data)
•Response: 0+0.012<CR><LF> (e.g. +0.012bar)
•Command: 0M2! (start measurement)
•Response: 00011<CR><LF> (2 measurements ready in 1 second)
•Response: 0<CR><LF> (Service Request)
•Command: 0D0! (send data)
•Response: 0-1.3<CR><LF> (e.g. -1.3°C)
•Command: 0C! (start measurement)
•Response: 000102<CR><LF> (2 measurements ready in 1 second)
•Command: 0D0! (send data)
•Response: 0+0.012-1.3<CR><LF> (e.g. +0.012bar, -1.3°C)
4.2.1.6 Extended Measurements Command
The VHPS measures two parameters: pressure and temperature. The extended M command allows to
retrieve the parameters individually.
•The "M1" command starts the pressure measurement.
•The "M2" command starts the temperature measurement.
Note that the procedure, the answer and the timing remain the same as explained for the basic M com-
mand.
•Command: aM1! Start pressure measurement, request measured values /o CRC-16
aM2! Start temperature measurement, request measured values /o CRC-16
checksum
•Response: atttn<CR><LF>
•Command: aMC1! Start pressure measurement, request measured values w/ CRC-16 check-
sum
aMC2! Start temperature measurement, request measured values w/ CRC-16
checksum
•Response: atttnccc<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)

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•ttt == time in seconds until measuring results are available
•n == no. of measured results/readings
on = 1 (one pressure or one temperature measured value)
•ccc CRC-16 checksum (3 characters)
The commands aM3!..aM9! and aMC3!..aMC9! are implemented, even though they do not result in any
meaningful information. A VHPS sensor always responds to these commands "a0000<CR><LF>”for a “M”
command and “a0000ccc<CR><LF>”for a “MC”command. The data logger should be able to understand
these responses as error messages.
4.2.1.7 Service Request (from sensor to data logger)
This command is initiated by the sensor if it has measuring results available earlier than assumed. An "M"
or "V" command has been sent by the data logger depending on the process. As a result, it informs the
data logger, that it now has measuring results available.
•Command: "M" or "V" command, depending on process
•Response: a<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
4.2.1.8 Start Concurrent Measurement Command
Starts a measurement in the sensor, while another sensor is still busy with its measurements (also "C"
command). With this command all measuring channels (pressure and temperature) are measured. The
sensor does not send a Service Request when it is finished with the measurements. The measuring results
must then be picked up with the "D" command. Measurements can be triggered in several sensors with
this command.
•Command: aC! Requesting of measured values without CRC-16 checksum
•Response: atttnn<CR><LF>
•Command: aCC! Requesting of measured values with CRC-16 checksum
•Response: atttnnccc<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•ttt == time in seconds until measuring results are available
•nn == nbr. of measuring results
nn = 02 (One pressure and one temperature measured value)
•ccc == CRC-16 checksum (3 characters)
4.2.1.9 Start Verification Command
This command is implemented in accordance with the SDI-12 standard but has no function behind.
•Command: aV!
•Response: a0000<CR><LF>

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where:
•a == sensor address (0, 1..9, A..Z, a..z)
Sending the “D”command to pick up the data is not necessary but allowed. The response after a “D”
command is always a<CR><LF>
4.2.1.10 Additional Concurrent Measurements Command
Measurements can be triggered in several sensors with this command. It starts a measurement in the
sensor, while another sensor is still busy with its measurements (also "C" command). This command is
intended for sensors which support several measuring variables (e.g. pressure, temperature). The "C1"
command starts the pressure measurement and the "C2" command the temperature measurement. The
sensor responds with the number of measurements and the time until these are ready. The sensor itself
does not send any measuring results. The sensor does not send a Service Request when it is finished with
the measurements. The measuring results must then be picked up with the "D" command.
•Command: aC1! Start pressure measurement, requesting of measured values without CRC-
16 checksum
aC2! Start temperature measurement, requesting of measured values without
CRC-16 checksum
•Response: atttnn<CR><LF>
•Command: aCC1! Start pressure measurement, requesting of measured values with CRC-16
checksum
aCC2! Start temperature measurement, requesting of measured values with CRC-
16 checksum
•Response: atttnnccc<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•ttt == time in seconds until measuring results are available
•nn == nbr. of measuring results
on = 01 (One pressure or temperature measured value)
•ccc == CRC-16 checksum (3 characters)
The commands aC3!..aC9! and aCC3!..aCC9! are implemented but have no function behind. In this case
the sensor responds always "a00000<CR><LF>”for a “C”command and “a00000ccc<CR><LF>” for a “CC”
command, which is interpreted as a fault message by the data logger.
4.2.1.11 Continuous Measurement Command
This command is implemented in according to the SDI-12 standard but has no function behind.
•Command: aR0...aR9! Requesting of measured values without CRC-16 checksum
•Response: a<CR><LF>
•

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•Command: aRC0...aRC9! Requesting of measured values with CRC-16 checksum
•Response: accc<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•ccc == CRC-16 checksum (3 characters)
4.2.2 CRC-16 Checksum
•Details see SDI-12 standard V1.3 chapter 4.4.12
4.2.3 SDI-12 extended commands
This chapter describes extended commands which extend the standard command set. All extended com-
mands are marked with an X as the first command character.
‼ Settings made by extended commands are volatile and not automatically saved. For permanent storage
use the save command (see 4.2.3.11). Caution: Settings must be explicitely saved to avoid loss during
power up.
4.2.3.1 Setting pressure unit
Causes the sensor to calculate measurement results in another unit. The measured value is output in the
selected pressure unit in future.
•Command: aXPnn!
•Response: ann<CR><LF> Sensor has switched to new unit
a0000<CR><LF> Has not recognized the new unit (fault message)
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•nn == index of unit (see table below)
Table 3 - Table of units: Index Unit
Index
Unit
00
factory settings
01
bar
02
mbar
03
mWC / m H2O
04
psi
05
ftWC
06
inH2O
‼ Settings made by extended commands are volatile and not automatically saved. For permanent storage
use the save command (see 4.2.3.11). Caution: Settings must be explicitely saved to avoid loss during
power up..
Example setting pressure unit
Initial condition: address: 0
unit: mWC
•Command: 0XP01! (change unit to bar)

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•Response: 001<CR><LF> (index of unit 01 = bar)
4.2.3.2 Reading pressure unit
Causes the sensor to output the selected unit.
•Command: aXP!
•Response: ann<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•nn == index of unit (see table below)
Table 4 - Table of units: Index Unit
Index
Unit
00
factory settings
01
bar
02
mbar
03
mWC / m H2O
04
psi
05
ftWC
06
inH2O
4.2.3.3 Setting recalibration value of zero-point pressure
Use this command for recalibration of zero-point pressure or reset the zero-point pressure recalibration
to default. The recalibration value <value> has to be in the adjusted unit. For reset to default set the
recalibration value to default zero-point pressure in the actually adjusted unit.
Further information for calculation recalibration value, recalibration procedure and recalibration exam-
ples please see chapter 5.
•Command: aXZZ<value>!
•Response: a<value><CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•<value> == recalibration value in the adjusted unit (max. 8 characters including sign
and decimal point)
‼ Settings made by extended commands are volatile and not automatically saved. For permanent storage
use the save command (see 4.2.3.11). Caution: Settings must be explicitly saved to avoid loss during power
up.
4.2.3.4 Reading recalibration value of zero-point pressure
Initiate the sensor to output the recalibration value of the zero-point pressure.
•Command: aXZZ!
•Response: a<value><CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)

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•<value> == recalibration value in the adjusted unit (max. 8 characters including sign)
4.2.3.5 Setting recalibration value of nominal pressure
Use this command for recalibration of nominal pressure or reset the nominal pressure recalibration to
default. The recalibration value <value> has to be in the adjusted unit. For reset to default set the recali-
bration value to default nominal pressure in the actually adjusted unit.
Further information for calculation recalibration value, recalibration procedure and recalibration exam-
ples please see 5.
•Command: aXZF<value>!
•Response: a<value><CR><LF>
where:
•a Sensor address (0, 1.9, A.Z, a.z)
•<value> recalibration value in the adjusted unit (max. 8 characters including sign and decimal
point)
‼ Settings made by extended commands are volatile and not automatically saved. For permanent storage
use the save command (see 4.2.3.11). Caution: Settings must be explicitly saved to avoid loss during power
up.
4.2.3.6 Reading recalibration value of nominal pressure
Initiate the sensor to output the recalibration value of the nominal pressure.
•Command: aXZF!
•Response: a<value><CR><LF>
where:
•a Sensor address (0, 1.9, A.Z, a.z)
•<value> recalibration value in the adjusted unit (max. 8 characters including sign and decimal
point)
4.2.3.7 Setting temperature unit
Causes the sensor to calculate measurement results in another unit. The measured value is output in the
selected temperature unit in future.
•Command: aXTn!
•Response: an<CR><LF> Sensor has switched to new unit
a0000<CR><LF> Has not recognized the new unit (fault message)
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•n == index of unit (see table below)
Table 5 - Table of units: Index Unit
Index
Unit
0
factory settings
1
°C

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2
°F
3
K
Settings made by extended commands are volatile and not automatically saved. For permanent storage
use the save command (see 4.2.3.11). Caution: Settings must be explicitly saved to avoid loss during power
up..
Example setting temperature unit
Initial condition: address: 0
unit: °C
•Command: 0XT2! (change unit to °F)
•Response: 02<CR><LF> (index of unit 2 = °F )
4.2.3.8 Reading temperature unit
Causes the sensor to output the selected unit.
•Command: aXT!
•Response: an<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•n == index of unit (see table below)
Table 6 - Table of units: Index Unit
Index
Unit
0
factory settings
1
°C
2
°F
3
K
4.2.3.9 Setting user identification string
Writes an identification string in the sensor. The identification string has a maximum length of 16 charac-
ters. Using this identification string, the customer can name the sensor as desired. It can use this to store
the measurement location of the sensor in the sensor.
•Command: aXI<string>!
•Response: a<string><CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•<string> == identification string (1..16 printable characters)
Settings made by extended commands are volatile and not automatically saved. For permanent storage
use the save command (see 4.2.3.11). Caution: Settings must be explicitely saved to avoid loss during
power up..

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4.2.3.10 Reading user identification string
Reads the identification string of the sensor. The identification string has a maximum length of 16 charac-
ters.
•Command: aXI!
•Response: a<string><CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
•<string> == identification string (1..16 printable characters)
4.2.3.11 Saving settings in flash memory
Causes the sensor to save all settings in the internal flash memory. This is necessary to save the changed
settings for the long term. This also retains the settings in case the power supply is interrupted. They can
be changed again at any time. If the settings are not saved, they will be lost when the sensor is restarted
(power supply is interrupted).
•Command: aXF!
•Response: a<CR><LF>
where:
•a == sensor address (0, 1..9, A..Z, a..z)
5Recalibration
Normally VHPS sensors have an excellent long-term stability. The sensors are factory-calibrated upon de-
livery.
Occasionally a recalibration could be necessary. For this situation it is possible to recalibrate the zero-
point and nominal pressure by use of a linear recalibration function. It is not possible to recalibrate errors
for more than 5%FS. In this case, please send the sensor back to HyQuest Solutions for recalibration. The
recalibration function is not intended for taring.
For recalibration we recommend using a pressure reference which is 5 times more precisely than the
sensor. Ensure that reference pressure is stable.
There are three different ways for recalibration: zero-point recalibration, nominal pressure recalibration.
In the following each procedure is explained step by step.
5.1 Zero-point pressure recalibration
1. Read out the actual recalibration value of nominal pressure -> PUserCalFullscaleold (see 4.2.3.6)
2. Read out the actual recalibration value of zero-point pressure -> PUserCalZeroold (see 4.2.3.4)
3. Set reference pressure (close to zero-point pressure) -> P1
4. Read out the pressure from the sensor -> S1 (with “M”and “D”Command)
5. Calculate the recalibration value if necessary (see below)

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6. Write the recalibration value to the sensor (see 4.2.3.3)
7. Set zero-point reference pressure
8. Read out the pressure from the sensor (with “M”and “D”Command)
9. Calculate the error (repeat procedure if necessary)
10. Save the recalibration value (see 4.2.3.11)
Calculation of zero-point pressure recalibration value
5.2 Nominal pressure recalibration
1. Read out the actual recalibration value of nominal pressure -> PUserCalFullscaleold (see 4.2.3.6)
2. Read out the actual recalibration value of zero-point pressure -> PUserCalZeroold (see 4.2.3.4)
3. Set reference pressure (close to nominal pressure) -> P2
4. Read out the pressure from the sensor -> S2 (with “M”and “D”Command)
5. Calculate the recalibration value if necessary (see below)
6. Write the recalibration value to the sensor (see 4.2.3.3)
7. Set nominal reference pressure
8. Read out the pressure from the sensor (with “M”and “D”Command)
9. Calculate the error (repeat procedure if necessary)

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10. Save the recalibration value (see 4.2.3.11)
Calculation of nominal pressure recalibration value
5.3 Zero-point and nominal pressure recalibration
1. Read out the actual recalibration value of nominal pressure -> PUserCalFullscaleold (see 4.2.3.6)
2. Read out the actual recalibration value of zero-point pressure -> PUserCalZeroold (see 4.2.3.4)
3. Set reference pressure (close to zero-point pressure) -> P1
4. Read out the pressure from the sensor -> S1 (with “M”and “D”Command)
5. Set reference pressure (close to nominal pressure) -> P2
6. Read out the pressure from the sensor -> S2 (with “M”and “D”Command)
7. Calculate the recalibration value if necessary (see below)
8. Write the recalibration value to the sensor (see 4.2.3.3)
9. Set zero-point reference pressure
10. Read out the pressure from the sensor (with “M”and “D”Command)
11. Set nominal reference pressure
12. Read out the pressure from the sensor (with “M”and “D”Command)
13. Calculate the error (repeat procedure if necessary)
14. Save the recalibration value (see 4.2.3.11)