LEYBOLD THERMOVAC TTR 101 N User manual

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THERMOVAC Transmitter
TTR 101 N, TTR 101 N S
Operating Manual 300544655_002_C1
Part Numbers:
230350V02
230351V02
230352V02
230353V02
230354V02
230355V02
230356V02
230366V02
230702V02

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Contents
Safety Information 3
0.1 Symbols used 3
0.2 Personnel Qualifications 3
0.3 General safety information 3
0.4 Liability and Warranty 5
Unpacking 6
Description 7
2.1 Technical Data 8
2.2 Dimensions 10
2.3 Accessories and replacement part numbers 12
Transmitter Installation (Mechanical) 13
3.1 Conforming utilization 13
3.2 Non-conforming utilization 13
3.3 Process compatibility 13
3.4 Vacuum connections 14
Transmitter Installation (Electrical) 15
4.1 Input/Output Wiring 16
4.2 Setpoint relays 18
Operations 20
5.1 Pressure output 20
5.2 Analog output 21
5.3 Sensor gas dependence 23
Functions 24
6.1 LED-ring/LED status indicator 24
6.2 Vacuum-zero adjustments and setpoint adjustments 25
6.3 User switch adjustments 27
6.4 Integrated touch display 31
FAQ (Frequently Asked Questions) 33
Trouble shooting 35
Maintenance 36
9.1 Transmitter maintenance: installation of replacement parts 36
Declaration of Contamination 38
Declaration of Conformity 40
Notes 41
Sales and Service 42

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Safety Information
0.1 Symbols used
The first two symbols identify other information in this manual that is essential or useful in achieving optimal
performance from the transmitter. The last symbol below is used throughout this manual to further define the safety
concerns associated with the product.
Calls attention to important procedures, practices or conditions.
0.2 Personnel Qualifications
0.3 General safety information
The safety instructions should always be followed during installation and operation of the transmitter.
Pass safety information to all users.
Adhere to the applicable regulations and take the necessary precautions for the process media used.
Consider possible reactions between the materials and the process media.
Consider possible reactions (e.g. explosion) of the process media due to the heat generated by the
product.
Adhere to the applicable regulations and take the necessary precautions for all work you are going to do
and consider the safety instructions in this document.
Before beginning to work, find out whether any vacuum components are contaminated. Adhere to the
relevant regulations and take the necessary precautions when handling contaminated parts.
Safety Precautions:
Failure to read message could result in damage to the equipment.
Refer to manual. Failure to read message could result in personal injury or serious damage to the equipment or
both.
All work described in this document may only be carried out by persons who have suitable technical training and
the necessary experience or who have been instructed by the end-user of the product.
Explosive Environments. Do not use the transmitter in presence of flammable gases or other
explosive environments.
Corrosive Environments. The transmitter is not intended for use in corrosive environments. Refer
to Transmitter installation chapter 4 of this manual.
Critical
Attention
Critical
!
!
Caution
!
Skilled personnel

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Service and Repair. Do not substitute parts or modify instrument other than described in chapter 9.
Do not install substituted parts or perform any unauthorized modification to the instrument. Return
the instrument to a Leybold Calibration and Service Center for service and repair to ensure all of the
safety features are maintained.
DANGER: contaminated parts
Contaminated parts can be detrimental to health and environment. Before beginning to work, find
out whether any parts are contaminated. Adhere to the relevant regulations and take the necessary
precautions when handling contaminated parts. If you need further support please contact Leybold.
Caution: vacuum component
Dirt and damages impair the function of the vacuum component. When handling vacuum
components, take appropriate measures to ensure cleanliness and prevent damages.
CE marking The transmitter complies with European standards for CE marking. Refer to
Declaration of Conformity chapter - of this manual.
Fuse. The transmitter power supply input has an internal thermal fuse. The fuse is self-recoverable
and should not be changed.
Electrical connections. The transmitter must be properly electrically connected in order to perform
according to the specifications.
Output pins are not protected against wrong electrical connections. Wrong electrical connections
can cause permanent damage to the transmitter or interference to measuring performance.
Refer to electrical connections description in chapter 4 of this manual.
Caution: dirt sensitive area
Touching the product or parts thereof with one's bare hands increases the desorption rate.
Always wear clean, lint-free gloves and use clean tools when working in this area.
Critical
!
!
!
Caution
!
Caution
!
Critical
!
Attention
!
!
Attention
!
Caution
!

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0.4 Liability and Warranty
Leybold assumes no liability and the warranty becomes null and void if the end-user or third parties
disregard the information in this document
use the product in a non-conforming manner
make any kind of interventions (modifications, alterations etc.) on the product
use the product with accessories not listed in the product documentation
The end-user assumes the responsibility in conjunction with the process media used. Transmitter failures due to contamination
are not covered by the warranty.

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Unpacking
Before unpacking your transmitter, check all surfaces of the packing material for shipping damage. Inspect for
visible damage. If found, notify the carrier immediately.
Please be sure that your transmitter package contains these items:
1 pcs. TTR 101 N THERMOVAC Transmitter
1 pcs. English short form manual (P/N: 300544668_002)
1 pcs. German short form manual (P/N: 300544668_001)
1 pcs. Product Inspection and Test Report
1 pcs. Pin for adjusting settings via button (only for P/N: 230350V02, 230351V02, 230352V02, 230353V02,
230354V02, 230355V02, 230356V02, 230366V02)
If any items are missing, please contact Leybold.

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Description
The TTR 101 N THERMOVAC series vacuum transmitters offer a wide measuring range from 5×10-5 to 1500 mbar
and are based on the measurement of thermal conductivity in a small cavity on a MEMS Pirani silicon chip sensor
and mechanical deflection of a silicon membrane in a Piezo sensor.
Transmitter versions with an RS232 digital communication interface (P/N: 230366V02) and EtherCAT digital
communication interface (P/N: 230702V02) can set up transmitter parameters and provide real time pressure
measurement. Please see the Communication Protocol 300544663 (RS232) and 300544664 (EtherCAT) for further
details. Transmitter versions with an integrated touchscreen display (P/N: 230354V02, 230355V02, 230356V02)
have the possibility to monitor essential transmitter parameters. Please see chapter 0 for further details.
The TTR 101 N THERMOVAC transmitters can be used in a variety of applications as standalone unit or with
Graphix controllers (P/N: 230680V01, 230681V01, 230682V01) and the Display controllers (P/N: 230001, 230024,
230025). All THERMOVAC transmitters are backward compatible with Graphix, Display and Center controllers.
Each transmitter is individually tested throughout the measuring range before leaving the factory. A test report is
included in the package. In addition, each transmitter pressure reading is individually temperature-compensated
within the specified operating temperature range.
The transmitters have up to three mechanical relays which can be used for process control, for example
interlocking valves or pumps. The analog voltage output can be interfaced to external analog equipment for
pressure readout or controlling.
Sensor technology
The transmitters contain two separate sensor elements. The MEMS Pirani (MEMS = Micro-Electro-Mechanical-
System) sensor element is based on measurement of thermal conductivity. The MEMS Pirani sensor consists of a
silicon chip with a heated resistive element forming one surface of a cavity. A cover on top of the chip forms the
other surface of the cavity. Due to the geometry of the sensor, convection cannot take place within the cavity and
consequently the sensor is insensitive to mounting position. Gas molecules are passed by diffusion only to the
heated element where the heat loss of the gas is measured.
The Piezo sensor is based on measurement of the mechanical deflection of a silicon membrane relative to an
integrated reference vacuum. The Piezo measures true absolute pressure independent of gas composition and
concentration.
Both sensor elements are very robust and can withstand high G-forces and instant air inrush.
Applications
The transmitters can be used in many different vacuum applications within the industrial application, research and
development, semiconductor, analytical and coating industries:
Loadlock pressure controlling
General vacuum pressure measurement
Fore line and roughing pressure measurement
Gas backfilling measurement and controlling
Mass spectrometer control
Activation of UHV gauge
System process control
Sense abnormal pressure and take appropriate security measure using set point relays
Control system pressure
Disposal
The TTR 101 N THERMOVAC transmitters are manufactured according to the RoHS directive.
For the benefit of the environment, at the end of life of the transmitter, it should not be disposed in
the normal unsorted waste stream. It should be deposited at an appropriate collection point or
facility to enable recovery or recycling.
Attention
!

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2.1 Technical Data
Measurement principle: Thermal conductivity according to a MEMS Pirani sensor
Mechanical deflection of a silicone membrane in a Piezo sensor
P/N: 230350V02, 230351V02, 230352V02, 230353V02, 230354V02, 230355V02, 230356V02:
Measurement range (N2and Air): 5×10-5 to 1500 mbar
Accuracy (1) (N2): 5×10-4 to 1x10-3 mbar: ±10% of reading
1 ×10-3 to 11 mbar: ± 5% of reading
11 to 1333 mbar: ± 0.75% of reading
1333 to 1500 mbar: ± 2% of reading
Repeatability (1) (N2): 1×10-3 to 11 mbar: ± 2% of reading
11 to 1067 mbar: ± 0.2% of reading
P/N: 230366V02, 230702V02:
Measuring range (N2and Air): 5×10-5 to 1500 mbar
Accuracy (1) (N2): MEMS Pirani: 5×10-4 to 1x10-3 mbar: ±10% of reading
1×10-3 to 100 mbar: ± 5% of reading
100 to 1000 mbar: ± 25% of reading
Abs. Piezo: 0.1 to 10 mbar: ± 1% of reading ± 0.5 mbar
10 to 1333 mbar: ± 0.75% of reading
1333 to 1500 mbar: ± 2% of reading
Repeatability (1) (N2): MEMS Pirani: 1x10-3 to 100 mbar: ± 2% of reading
Abs. Piezo: 10 to 1067 mbar: ± 0.2% of reading
Supply Voltage: 9 –30 VDC
Power consumption: < 1.2 Watt
Fuse (thermal recoverable): 200 mA
Analog output: 0.61 –10.23 VDC, Log 1.286 VDC/decade
Analog output resolution: 16 bit
Analog output impedance: 100 Ω
Analog output update rate: 16 Hz
Sensor fail, analog output: 0 V

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Mechanical setpoint relays:
P/N: 230350V02, 230351V02, 230354V02, 230355V02: 0
P/N: 230352V02, 230353V02, 230356V02: 2
P/N: 230366V02: 3
Setpoint relay range: 2×10-4 to 1300 mbar
Setpoint relay contact rating: 1 A / 30 VDC/AC (resistive load)
Setpoint relay response time: < 100 ms
Setpoint relay contact resistance: 100 mΩ (max)
Setpoint relay contact endurance: 100,000 cycles (min) (30 VDC/1 A load)
Setpoint relay contact endurance: 2,000,000 cycles (min) (30 VDC/0.2 A load)
Software setpoint relays:
P/N: 230702V02: 2
Response time: < 20 ms
Digital interface cycle time: 1 ms
Materials exposed to vacuum (2): 304 stainless steel, sealing material FPM
Internal volume: KF16 flange 2.8 cm3
NPT 1/8” 3.1 cm3
Housing material: Stainless steel 304
Flange material: Stainless steel 304
Weight:
P/N: 230350V02, 230352V02, 230366V02: 168 g
P/N: 230351V02, 230353V023: 183 g
P/N: 230354V02, 230356V02: 292 g
P/N: 230355V02: 307 g
P/N: 230702V02: 338 g
Maximum allowed pressure: 3 bar
Operating temperature: 0 to 40 °C (32 to 104 °F)
Bake out temperature (Power off): 85 °C (185 °F)
Filament temperature: 35 °C above ambient temperature
Humidity: 0 –95% Non-condensing
Ingress Protection Rating: IP40
Leak rate: < 5∙10-9 mbar∙l/s
(1) Accuracy and repeatability are typical values measured in Nitrogen atmosphere after zero adjustment at
ambient temperature.
(2) For the full list of all materials exposed to process gases please contact LEYBOLD.

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2.2 Dimensions
[mm]
P/N: 230702V02
P/N: 230354V02 to 230356V2

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P/N: 230366V02
P/N: 230350V02 to 230353V02
Flanges:
KF 16
NPT 1/8”

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2.3 Accessories and replacement part numbers
Part
Part no.
TTR 101 N, DN16KF
230350V02
TTR 101 N, 1/8" NPT
230351V02
TTR 101 N, DN16 KF, 2SP
230352V02
TTR 101 N, 1/8" NPT, 2SP
230353V02
TTR 101 N, DN16 KF, Display
230354V02
TTR 101 N, 1/8 NPT, Display
230355V02
TTR 101 N, DN16 KF, Display, 2SP
230356V02
TTR 101 N, DN16 KF, RS232, 3SP
230366V02
TTR 101 N, DN16 KF, EtherCat
230702V02
Replacement sensor, TTR 101 N, DN16 KF
230361V02
Replacement sensor, TTR 101 N, 1/8" NPT
230362V02
Display One
230001
Display Two
230024
Display Three
230025
Graphix One
230680V01
Graphix Two
230681V01
Graphix Three
230682V01
Cables Type A 5 Meter
12426
Cables Type A 10 Meter
230012
Cables Type A 15 Meter
12427
Cables Type A 20 Meter
12428
Cables Type A 30 Meter
12429
Cables Type A 50 Meter
12431
Cables Type A 75 Meter
12432
Cables Type A 100 Meter
12433
Spiral tube DN 16 ISO-KF
230082
Centering Rings (Stainless Steel 1.4305) with O-Ring,
DN16 KF
88346
Centering Rings (Stainless Steel) with Sintered Metal Filter,
DN16 KF
88351
Clamping Rings (Aluminum), DN16 KF
18341
Centering Ring with fine filter DN16 KF
88396

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Transmitter Installation (Mechanical)
3.1 Conforming utilization
The transmitter is intended for measuring pressure.
The transmitters are intended for use in relatively clean environments.
The transmitter can only be used by persons who have suitable technical training and the necessary
experience or who have been instructed by the end-user of the product.
Always ensure that all vacuum sealing items and surfaces are clean, without damage and free of particles.
Use a cable with strain relief to ensure proper electrical connection and to reduce stress on the connectors.
To comply with EN61326-1 immunity requirements, use a braided, shielded cable.
3.2 Non-conforming utilization
The transmitter cannot be used for measurements other than described in this manual.
The transmitters are not intended for use in dirty and corrosive environments
Do not use the transmitter in presence of flammable gases or other explosive environments.
Do not install substituted parts or perform any unauthorized modification to the instrument.
The transmitter is not intended for use above maximum allowed pressure.
3.3 Process compatibility
The TTR 101 N THERMOVAC transmitters are intended for use in relatively
clean environments. The transmitter cannot be used in corrosive environments
like a semiconductor etch process chamber where aggressive gases like
fluorine are used.
If the transmitter is located close to a gas source connection like a flow
controller or leak valve the transmitter pressure measurement can be higher
than the actual chamber pressure. Location close to a pumping system
connection can cause a lower pressure measurement than actual chamber
pressure.
The transmitters and their sensor design can be mounted in any orientation
without compromising accuracy. However it is not recommended to mount the
transmitters upside down, as dust and dirt might fall into the sensor.
Explosive Environments
The sensor filament is kept at a low temperature of only 35 °C above ambient temperature, however in case of
malfunction in the sensor element can exceed normal operating temperature and consequently the transmitter
should not be used in explosive environments.
Do not use or install the transmitter where the following conditions occur:
- Temperatures lower than 0 °C or higher than 40 °C
- Corrosive or explosive gases
- Direct sunlight or other heat sources
!
Not recommended
Caution
!
!

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Temperature
The transmitter has an active and individual sensor temperature compensation circuit that ensures accurate
measurement in a wide temperature range.
For best measuring performance avoid large temperature gradients and direct cooling like air-condition air stream
or heating like a pump exhaust stream.
Bake out
The transmitter electronics can withstand maximum 85 °C (185 °F) when the power is turned off.
Contamination
Locate and orient the transmitter where contamination is least likely. The sensor has a low filament temperature of
only 35°C above ambient temperature; therefore, the sensor is less prone to contamination by cracking products
from fore vacuum pump oil.
Vibrations and instant air inrush
The sensor elements are extremely robust to mechanical forces like vibration and G-forces. The sensor element
cannot be damaged by fast and repeated pressure cycles or instant inrush of air.
3.4 Vacuum connections
The transmitters are available with different types of vacuum fittings. When mounting the transmitter, always
ensure that all vacuum sealing items and surfaces are clean, without damage and free of particles. Do not touch
the vacuum flange sealing surface.
Pressure range
The standard TTR 101 N THERMOVAC transmitter are internally sealed with elastomer FPM sealing and is
intended for use in the pressure range 5×10-5 to 1500 mbar. If used in UHV applications the out gassing rate of
FPM can be too high.
If the transmitter is backfilled with a liquid like pump oil the sensor element is likely permanently
damaged. The transmitter cannot be cleaned using solvents.
If the transmitter will be exposed to pressures above atmospheric pressure make sure that proper
vacuum fittings are used. Ensure that the internal system pressure is at ambient pressure
conditions before opening the vacuum system and removing any connections.
Attention
Caution
!
!
!
!

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Transmitter Installation (Electrical)
TTR 101 N THERMOVAC transmitters are available with different input/output connectors. Use a cable with strain
relief to ensure proper electrical connection and to reduce stress on the connectors.
To comply with EN61326-1 immunity requirements, use a braided shielded cable. Connect the braid to the metal
hoods at both ends of the cable with the end for power supply connected to earth ground.
Ground loops, differences of potential, or EMC problems may affect the measurement signal. For optimum signal
quality, please do observe the following notes:
Use an overall metal braided shielded cable. The connector must have a metal case.
Connect the cable shield to ground at one side via the connector case. Make sure the connector case has
direct contact to the cable's shield on its whole circumference. Do not connect the other side of the shield.
Connect the supply common with protective ground directly at the power.
Use differential measurement input (signal common and supply common conducted separately).
Potential difference between supply common and housing ≤18 V (overvoltage protection).
The power supply input is 9 to 30 VDC. The power supply input is protected by an internal thermal fuse. The fuse is
self-recoverable; do not replace it. Damage may occur to the circuitry if excessive voltage is applied, polarity
reversed or if a wrong connection is made.
If using the analog voltage output, connect the positive analog out and negative analog out pins to a differential
input voltmeter or an analog-to-digital (A/D) converter. Do not connect the negative side of the analog output to the
negative side of the power supply input or to any other ground. Doing so will cause half of the power current to flow
through this wire. Measurement errors in the output voltage may be seen due to the voltage drop from this current.
The longer the cable, the worse the error will be. Do not connect the set point relay terminals to the analog output.
Correct connection of analog output to floating input
Incorrect connection of analog output to non-floating input
Ensure a low impedance electrical connection between the transmitter body and the grounded
vacuum system to shield the sensor from external electromagnetic sources.
Ensure that the analog output is connected to floating input.
Attention
!
!

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4.1 Input/Output Wiring
To comply with EN61326-1 immunity requirements, use a braided, shielded cable. Connect the braid to the metal
hoods at both ends of the cable with the end for power supply connected to earth ground.
Part Numbers: 230366V02:
I/O Connector (15 pin HD Sub D male )
PIN Description
1
RS232 Transmit
9
Relay 1, Normally Closed
2
RS232 Receive
10
Relay 2, Normally Closed
3
Power + (9-30 VDC)
11
Relay 2, Common
4
Power return - (GND)
12
Relay 2, Normally Open
5
Analog Output +
13
Relay 3, Normally Closed
6
Analog Output -
14
Relay 3, Common
7
Relay 1, Normally Open
15
Relay 3, Normally Open
8
Relay 1, Common
Part Numbers: 230350V02, 230351V02, 230354V02, 230355V02:
I/O Connector (8 pin RJ45/FCC68)
PIN Description
1
Power + (9-30 VDC)
5
Analog Output -
2
Power return - (GND)
6
Not Connected
3
Analog Output +
7
Not Connected
4
ID-Resistor, 71.5 kΩ (±1%)
8
Not Connected

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Part Numbers: 230352V02, 230353V02, 230356V02:
I/O Connector (8 pin RJ45/FCC68)
PIN Description
1
Power + (9-30 VDC)
5
Analog Output -
2
Power return - (GND)
6
Relay Setpoint 2 (closing contact)
3
Analog Output + (or SP1/2 thresholds)
7
Relay Setpoint 1 (closing contact)
4
ID-Resistor, 71.5 kΩ (±1%)
8
Relay Setpoint 1 and 2 Common
Part Numbers: 230702V02:
2 x I/O Connector (8 pin RJ45/FCC68): <IN> and <OUT>
PIN Description
1
TD+
5
Not Connected
2
TD-
6
RD-
3
RD+
7
Not Connected
4
Not Connected
8
Not Connected
Part Numbers: 230702V02:
I/O Connector (15 pin HD Sub D male )
PIN Description
1
Not Connected
9
Not Connected
2
Not Connected
10
Not Connected
3
Power + (9-30 VDC)
11
Not Connected
4
Power return - (GND)
12
Not Connected
5
Analog Output +
13
Not Connected
6
Analog Output -
14
Not Connected
7
Not Connected
15
Chassis GND
8
Not Connected

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4.2 Setpoint relays
The TTR 101 N THERMOVAC transmitters have up to three mechanical relays that can be used for controlling
external process equipment. The relays have closing and breaking contacts and the contacts are rated 30 VDC, 1 A,
resistive load. For the setup of the setpoints, refer to chapter 6.
Inductive relay load
Special precautions should be taken when driving inductive loads with the relay contact. When an inductive load
like a solenoid is energized, the in-rush current is significant higher than the regular load current. In-rush currents
exceeding the relay contact rating can cause reduction of relay contact life time or contact reliability.
When a solenoid is de-energized, the collapsing magnetic field can cause significant voltage spikes. These spikes
can couple capacitively from cable to cable and interfere with measuring electronics or transmitter signal.
An arc suppression network, as shown schematically to the right, is
recommended. The values of the capacitance C and the resistance R can
be calculated by the following equations:
C = I2/(1 x 107) R = E/ Ia
where:
C is in Farads. R is in ohms
I is DC or ACpeak load current in amperes. E is DC or ACpeak source voltage in volts
a = 1 + (50/ E)
Note that Rmin = 0.5 Ω and Cmin = 1×10-9 F, D is a fast transient suppression diode.
Setpoint functionality
The set point relays can be activated either above or below the set point values. The graphs below show the
different relays stages in either below or above configuration. The NC contact will always be closed in case of
power failure.
Driving inductive loads via the setpoint relay contacts requires de-energizing spike protection.
Inadequate protection can cause permanent damage to the transmitter or interfere with the analog
output signal.
Always ensure that inductive in-rush currents do not exceed relay contact rating.
When using the setpoint relay to control process equipment always take appropriate precautions to
prevent system damage in case of transmitter power failure. The NC contact will be closed in case
of transmitter power failure.
Critical
!
Critical
!

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Please see the Leybold vacuum transmitter Communication Protocol 300544663 (RS232) for further details.
To adjust the set point relays to above or below switching functionality you must follow the procedure like described
in chapter 6.3 (for units without RS232 interface).
It is important to understand that when the signal is declining during adjustment you will set the below function and
if the signal is increasing you will set the above function.
To change the direction of signal adjustment, you must keep the button pressed until reaching top or low end of the
set point range, then the signal will change its direction.

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Operations
5.1 Pressure output
The TTR 101N THERMOVAC transmitters can provide pressure measurement output as an analog voltage, RS232
digital value (P/N: 230366V02) or EtherCAT digital value (P/N: 230702V02). For details about the digital interface,
please refer to the Communication Protocol 300544663 (RS232) and 300544664 (EtherCAT).
The analog output is per default based on the MEMS Pirani and Piezo absolute combined reading and provides a
16 bit voltage output of 1.286 VDC/decade standard configuration. Refer to chapter 5.2 for details.
The Piezo absolute reading and the MEMS Pirani reading are combined into one smooth pressure reading with
superior measurement performance throughout the entire pressure range of more than 8 decades.
The measurement switching is gas dependent with the following pressure values:
Combined reading measurement
Gas setup
MEMS Pirani
Reading
MEMS Pirani /Piezo
absolute integration
Piezo absolute
Reading
All gas settings
<6.7 mbar
6.7-14.7 mbar
>14.7 mbar
Resolution
The digital pressure output can provide three digit or four digit values. However, the resolution is limited in certain
parts of the measuring range.
1x10-5 to 1x10-4 mbar one digit resolution 1.000x10-5
1x10-4 to 1x10-3 mbar two digit resolution 1.200x10-4
1x10-3 to 900 mbar three or four digit resolution 1.234x10-3
Measuring noise
External sources can interfere with the sensor signal and cause noise on the signal. The low measuring range is
most sensitive to measuring noise due to low signal levels.
When designing external pressure control loops make sure that external equipment like pumping
system is not damaged if the transmitter output enters Sensor defect mode or in case of power
failure.
When designing pressure data collecting software and controlling loop make sure that the software
does not interpret a communication error as a valid pressure value.
Caution
Caution
!
!
!
!