Sensor Technologies
Basic Product Training 2010
June 2010, Dr. Horst Bleichert
Sensor Technology
Overview
Electrochemical Sensor (EC)
Toxic Gases and Oxygen
Catalytic Bead Sensors (CatEx)
Flammable Gases
Infrared Sensors (IR)
Flammable Gases and CO2
PID Sensors
Volatile Organic Compounds (VOCs)
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Sensor Technology
Electrochemical Sensors (EC)
The gas to be detected enters the sensor via a dust / water repellent membrane.
The gas dissolves in the electrolyte.
At the surface of the measuring electrode the gas reacts.
Based on the chemical reaction an electrical current is generated.
The electrical current is proportional to the gas concentration.
Examples:
CO – Sensor:
+
CO + H O CO + 2 H + 2 e - Measuring Electrode
2
2
-
+
½ O + 2 H + 2 e H O Counter Electrode
2
2
O – Sensor:
2
-
O + 4 H + 4 e 2 H O Measuring Electrode
+
2
2
-
+
2 H O O + 4 H + 4 e Counter Electrode
2
2
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Sensor Technology
Electrochemical Sensors (EC): Detection of Toxic Gases and Oxygen
H S - Gas
2
Diffusion- Dust / Water-Filter
Measuring Membrane
Electrode
Electrolyte
Reference Electrode
Counter Electrode
Dr. Horst Bleichert Sensor Technologies
Sensor Technology
Electrochemical Sensors (EC)
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Sensor Technology
Electrochemical Sensors (EC)
How can an EC Sensor be selective to a special gas?
• Catalytic material of the measuring electrode
• Electric potential of the measuring electrode against the reference
electrode
With the patented (H2S, CO, O2) 3-electrode technology warranties
to 5 years are possible.
For the XS R O this is unique in the world.
2
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Sensor Technology
Electrochemical Sensors (EC)
Pac III
Multiwarn/MiniWarn
X-am 3000
X-am 7000
Pac 1/3/5/7000
Pac 3500/5500
X-am 1/2/5x00
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Sensor Technology
CatEx - Sensors
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Sensor Technology
CatEx - Sensors
A catalyst enhances the reaction between oxygen in the air and combustible
substances.
This oxidation reaction produces heat.
The heat of this reaction increases the electrical resistance in the detector
element.
The increase in resistance changes the electric current in the Wheatstone bridge.
The signal is proportional to the gas concentration and is displayed as % LEL.
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Sensor Technology
CatEx - Sensors
Water
Carbon Dioxide
Oxygen
Methane
Water
Oxygen
Heat
Hot
Catalyst
CH + 2 O CO + 2 H O + Heat of Reaction
2
4
2
2
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Sensor Technology
CatEx – Sensors: Detection of Flammable Gases and Vapours
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Sensor Technology
CatEx - Sensors
Smart Sensor Technology for X-am 7000
Several relevant parameters are stored in the built-in data
store (EEPROM):
Type of sensor, target gas, measuring range, temperature
compensation, alarm levels and calibration data.
Therefore you can exchange a Smart Sensor from one
instrument into another instrument without new calibration.
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Sensor Technology
Infrared - Sensors (IR): Detection of Flammable Gases and CO2
Sapphire Window
IR-Source (Lamp)
Reference Detector
Reflector
Measuring
Detector
Dust Filter
Beam Splitter
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Sensor Technology
Infrared - Sensors (IR)
8 – double detector
9 – pcb with EEPROM
10 - plug
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Sensor Technology
Infrared - Sensors (IR)
Lamp Gas Cuvette Interference Filter Detector
Air
Only green light can pass.
Gas
Green light is missing: Gas is present.
Green light is absorbed by gas.
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Sensor Technology
Infrared – Sensors (IR)
Gas is pumped or diffuses into a chamber with an IR light source.
The targeted gas(es) absorb the IR light energy.
The detector on the other side of the chamber
measures how much light is absorbed by the targeted compound(s).
A compensation detector corrects for IR light
blockage caused by dust, water and other contaminants.
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Sensor Technology
Infrared - Sensors (IR)
IR EX
Detects many explosive gases
(except H and Acetylene)
2
IR CO 2
0 - 5 %vol CO 2
IR CO - HC
2
0 - 100 %vol CO 2
The smart IR-Ex sensors are used in the X-am 7000.
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Sensortechnologien
Infrarot - Sensors (IR) – Dual IR Sensor
gold plated reflecting sensor grills
for a direct gas access and a quick
response
plastic housing with gold plated
chamber
CO double detector
2
Ex double detector
Infrared lamp
PCB with flex cable and sensor
heating elements
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Sensor Technology
Infrared – Sensors (IR)
IR EX
0 - 100 % by vol. Ex / 0 - 100 %LEL
Detects many explosive gases (except
H and Acetylene)
2
IR CO 2
0 - 5 % by vol. CO 2
Dual IR Ex / CO
2
0 - 5 % by vol. CO 2
0 - 100 % by vol. Ex / 0 - 100 %LEL
The Dual IR Ex / CO sensors are used in the X-am 5600.
2
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Sensor Technology
Infrared – Sensors (IR)
IR-Technology versus CatEx-Technology
Infrared operates in environments even with low or no Oxygen concentrations.
Infrared is completely immune to poisoning and inhibiting compounds, that effect CatEx - sensors.
Both types measure % LEL and % by volume concentrations of various flammable gases.
Due to its long life a 5 year warranty can be granted for IR - sensors.
A small disadvantage:
With IR-Ex sensors it is not possible to measure Hydrogen and Acetylene
- in the Dräger X-am 7000 the Cat-Ex or EC sensor will do this job
- in the Dräger X-am 5600 the XXS H2 HC can be used to receive an added H Ex signal.
2
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Sensor Technology
PID – Sensors: Detection of Volatile Organic Compounds VOCs
Principle of Operation: PID = Photo Ionization Detector
UV - Lamp
+
- - - -
+ + + +
_
The current is measured
Gas diffusion Ionized gas and the concentration is
displayed.
The ionized gas passes the capacitor plates
The gas passes and produces an electrical current.
the 10.6 eV UV-lamp. The
photons ionize the gas.
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Sensor Technology
PID – Sensors
A PID will detect any gas with an ionization potential lower than the lamp energy.
Examples for ionization-potentials in eV:
Toluene 8.82
Trichloroethylene 9.45 Detectable with the
Carbon Disulphide 10.13
Trichloroethane 11.25 10.6 eV PID lamp
Oxygen 12.08
PIDs have no selectivity !
They measure the sum of gases which are present (if ionized by the lamp).
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Sensor Technology
PID – Sensors
Dräger Multi-PID 2 for Leak-Detection of VOCs
Smart PID sensor for Dräger X-am 7000
A possible sensor-modification for very low concentrations (ppb range)
would allow us to detect Benzene with the X-am 7000.
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Sensor Technology
PID – Sensors
Smart PID Sensor for X-am 7000
“Plug and Play“:
Easy sensor change => automatic configuration
Sensor-chip contains all sensor data
Pre-calibrated
Database of 20 gases and vapours + 3 free programmable gas channels
NOTE:
The Smart PID Sensor works together with the Dräger X-am 7000 software
version 1.60 and higher.
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Sensor Technology
PID – Sensors
Smart PID
Measurement Range: 1 – 2,000 ppm
Detection with: 10.6 eV Lamp
Detection Limit: 1 ppm
T 0…20 - Time (Pump): 10 sec
T 0…20 - Time (Diffusion): 15 sec
Lifetime of Lamp: 8,000 h
Warranty: 2 years on the sensor
1 year on the lamp
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Sensor Technology
Key Success factors with Unique DrägerSensors
A high measuring performance already is Dräger standard.
Key success factors for the future are:
Small
Lightweight
Long Lifetime Sensor-Technology
Low Power Consumption Key success factors with unique
Low Production Costs
DrägerSensors
Small competitive portable instruments
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Dräger Gas Detection Technology
Applications
CSE
Confined Space Entry
AM PAM
Area Monitoring Personal Air Monitoring
LS
Leckage Search
Overview Portable Gas Detection | Gas Detection | 99 | 26
March 2013
Dräger Gas Detection Technology Confined Space Entry
Confined Space Entry CSE
•Maintenance and repair work often require people to climb into confined
spaces. These areas of work can be especially dangerous because of the
lack of space, the lack of ventilation, and the presence or development of
hazardous substances.
•A clearance measurement is required before entry. Multi-gas instruments
are used together with corresponding pumps and accessories such as hoses
and probes. After a successful measurement, where no hazards have been
detected, the same instruments can be used for continuous personal
monitoring while working in the confined space.
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