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LFE CONTHOS 3 - TCD
The LFE CONTHOS 3 TCD family consists of high-performance thermal conductivity gas analyzers engineered for continuous, online monitoring in demanding industrial environments. Combining a proven measurement principle with modern microprocessor control, they ensure stable, precise results around the clock.
Backed by more than 40 years of TCD expertise, LFE analyzers are built around a highly stable detector offering fast response and exceptional corrosion resistance. Whether used for hydrogen purity monitoring or advanced process control in steel, chemical, and other industries, CONTHOS 3 gas analyzers deliver the accuracy and long-term reliability that engineers and researchers rely on.
Key Features
- Quick response
Micro-miniaturized detector design - Excellent long-term stability
- Very low detection limits
Well below the thresholds of conventional TCD designs. - Flow-independent response
- NAMUR-compliant user interface
- Outstanding corrosion resistance
Detector constructed from premium materials: aluminum oxide (Al2O3), glass, and SiOx-coated platinum sensor filaments - Ideal for hydrogen purity monitoring
- Suitable for a wide range of gases and concentration levels
- Thermostat-controlled TCD (50–180°C)
- Comprehensive self-diagnostics
Typical Applications
- H2 and O2 purity in electrolysis of water
- Monitoring of hydrogen in turbogenerators
- Metallurgical process gases such as blast furnaces, converter steel or direct reduction
- Metallurgical process gases such as nitration and nitrocarburizing
- Steel industry: Heat treatment & hardening
- Monitoring of gas purity, pressure swing adsorption and LEL/UEL
- Petrochemistry: Flammable gases in hazardous areas
- Gas processing to synthesis/ reformer gas & coal gasification
Housing Options
Housing Options
- The CONTHOS 3 – TCD is available in various housing options for different installation environments.
- All versions use the same TCD detector and offer identical measurement performance.
General Purpose Models
Models for Hazardous Areas
Special Model
CONTHOS 3E-TCD
General purpose
19" rack housing
(protective class IP40)
CONTHOS 3F-TCD
General purpose
Field housing
(protective class IP65)
CONTHOS 3-TCD Ex d
Transmitter
Explosion protected
IECEx / ATEX version
for ex zones 1 & 2
CONTHOS 3F-TCD Ex p
Explosion protected
ATEX version
for ex zones 1 & 2
CONTHOS 3F-TCD HT
High temperature version
General purpose
Field housing
(protective class IP65)
Common Options
- Up to 3 switchable ranges: independently configurable, suppressed & absolute (non-suppressed)
- Dynamic interference correction of accompanying components in multi-component gas mixtures in conjunction with external, selective gas analyzers
- Digital I/O board for remote range switching, range identification, threshold contacts, etc.
- RS-485 interface with Modbus RTU protocol
- Modbus TCP
LFE’s Thermal Conductivity Detector
LFE’s Advanced Thermal Conductivity Detector
Conventional thermal conductivity analyzers use a heated element suspended in the sample gas. As electrical current warms the element, it reaches a thermal equilibrium determined largely by the gas’s thermal conductivity. The analyzer then infers gas composition from the resulting change in the element’s electrical resistance. While effective, this approach ties heating and temperature measurement to the same component, making the signal susceptible to drift, flow-rate effects, and convection.
LFE’s detector refines this classical principle by spatially and electrically separating the heating element from the temperature-sensing filament. This innovative geometry, combined with precise thermal management, minimizes free and forced convection effects and greatly improves measurement stability. The result is a detector that provides fast, highly stable readings without the usual trade-off between gas flow and response time.
A further advantage of this design is its ability to support multiple, physically optimized measurement ranges within a single detector. For example, a triple-range CONTHOS system can measure 0–0.5 vol.% H2 in O2, 99.5% H2 in O2 (0–5000 ppm O2 in H2), and 0–100% H2 — all using the same TCD unit.
Conventional TCD analyzers cannot offer this flexibility. Conventional systems configured for hydrogen purity measurement, for example, typically require helium as the bridge-balancing gas, which leads to signal drift and limits the usable measurement range. As a result, a conventional detector optimized for one end of the concentration spectrum cannot accurately measure at the other. LFE’s detector design avoids these limitations entirely, enabling stable, wide-range performance without dependence on balance gases.
This advanced detector architecture has been at the core of every CONTHOS TCD process gas analyzer since the early 1980s and remains fundamental to its industry-leading accuracy, stability, and application versatility.
Technical Data
Technical Data
Enclosure & Electrical Data
| CONTHOS 3E 19”-rack housing | CONTHOS 3F field housing | CONTHOS 3 - Ex d IECEx/ATEX compliant Exd Transmitter | CONTHOS 3F - Ex p ATEX compliant Exp system | CONTHOS 3F - HT high temperature version | |
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Technical specifications subject to change without notice |
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for mounting in 19" cabinet |
purgeable steel housing for wall mounting; with separate compartments for the electronic components and the analytical components |
wall-mounted Ex d enclosure made of light metal flameproof enclosure (CONTHOS 3E or 3F control unit located in safe area required) |
purgeable steel housing for wall mounting; with separate compartments for the electronic components and the analytical components | purgeable steel housing for wall mounting; with separate compartments for the electronic components and the analytical components | |
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Enclosure & electrical data |
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Dimensions |
133 x 483 x 427 mm (3U / 84HP) 434 x 460 x 270 mm |
434 x 460 x 270 mm | 433 x 410 x 281 mm | 490 x 460 x 270 mm | 502 x 460 x 270 mm |
| Protection class | IP40 | IP65 | IP66 | IP65 | IP65 |
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Electrical hazardous area class |
TCD transmitter* (*CONTHOS 3E or 3F control unit located in safe area required) |
Ex protective class of system: II 2 G, Ex p II T4 |
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| Weight | approx. 10 kg | approx. 25 kg | approx. 35 kg | approx. 30 kg | approx. 25 kg |
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Power requirements |
100-240 VAC (48-62Hz; nominal voltage range: 88-253 VAC; 100 VA max. during warm-up period) |
100-240 VAC (48-62Hz; nominal voltage range: 88-253 VAC; 130 VA max. during warm-up period) | |||
Measuring Characteristics
| Common Technical Data CONTHOS 3E | CONTHOS 3F | CONTHOS 3-Transmitter - Ex d | CONTHOS 3F - Ex p | CONTHOS 3F - HT | |||||
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Technical specifications subject to change without notice |
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Measuring characteristics |
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Measuring principle |
Thermal conductivity (TCD). Difference in thermal conductivity (Δλ) of various gases |
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Measuring ranges |
Up to 3 linearized, independently configurable, switchable ranges. lowest range: 0 - 0.5% H2 in N2 or 99.5-100% H2 in N2 (or equivalent Δλ) |
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Calibration |
Manual: 2-point (zero / span) calibration |
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Response time t90 |
≤ 3 sec (at 60 l/h gas flow and minimum signal dampening level) |
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Influence of gas flow |
between 3 - 30 l/h: < 0.5% of range span for a gas flow change of ±10 l/h Higher flow rates up to e.g. 120 l/h are possible. At these higher flow rates it is recommended that the analyzer be calibrated at the operating flow rate. |
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Pressure influence |
The TCD principle has a normally negligible pressure dependency. At very low ranges it can be seen as a proportional signal offset. |
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Detection limit 1 |
≤ 0.5% of span (at signal dampening level: 1 sec) |
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Linearity/ Accuracy 1 |
≤ 0.5% of span |
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Reproducibility 1 |
≤ 0.5% of span |
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Response drift 1 |
Zero: ≤ 1% of span per week |
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Ambient temperature influence |
Zero: ≤ 1% of span per 10 K |
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Ambient temperature in operation |
allowed temperature range : +5 to +45°C |
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Influence of inclination |
no influence |
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Materials
| CONTHOS 3E 19”-rack housing | CONTHOS 3F field housing | CONTHOS 3 - Ex d IECEx/ATEX compliant Exd Transmitter | CONTHOS 3F - Ex p ATEX compliant Exp system | CONTHOS 3F - HT high temperature version | |
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Technical specifications subject to change without notice |
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Materials in contact with sample gas |
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TC Detector |
Al2O3-ceramic and sapphire, glass and SiOx-coated Pt measuring filaments |
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Internal gas lines |
Standard: PTFE / PFA |
Stainless steel tubing |
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Sample gas connectors |
Standard: Swagelok® connectors |
o.d. ø1/4" stainless steel tubing | Swagelok® connectors stainless steel (SS 316; similar to 1.4401) for ø6mm tubing |
Standard: Swagelok® connectors stainless steel (SS 316; similar to 1.4401) for ø6mm tubing |
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Optional: Swagelok® connectors for ø¼" tubing Optional: NPT 1/4" (female) Optional : PFA connectors for synthetic tubing DN 4/6 |
Optional: Swagelok® connectors for ø1/4" tubing |
Optional: Swagelok® connectors for ø1/4" tubing |
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Instrument Interface
| Common Technical Data CONTHOS 3E | CONTHOS 3F | CONTHOS 3-Transmitter - Ex d | CONTHOS 3F - Ex p | CONTHOS 3F - HT | |||||
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Technical specifications subject to change without notice |
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Data display, inputs and outputs |
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User Interface |
LC-display (40 characters x 16 lines) + bar graph |
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Analog signal output |
2 independently configurable, galvanically isolated analog outputs (with common ground; RLoad = 600 Ohm max) |
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Digital outputs |
Instrument status (NAMUR NE 107 compliant) via floating contacts (28 V max.; 350 mA max.) |
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Analog inputs |
3 galvanically isolated, configurable analog inputs for interference correction |
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Interference correction |
3 correction channels for static and/or dynamic interference correction (dynamic correction only in conjunction with the optional analog inputs or Modbus interface (RS-485 or TCP) |
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Digital I/O |
Digital inputs: 8 configurable, optically isolated inputs (6 - 24 VDC; 10 mA max.)
Digital outputs: 7 configurable, floating relay contacts (28 V max.; 350 mA max.)
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Modbus interface |
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Service interface |
non-isolated serial interface for accessing the instrument's configuration via a proprietary PC software |
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1 at constant temperature and pressure
- The stability data is valid for analyzer operation with pure bottled gases. Instrument accuracy is based on binary or quasi-binary gas mixtures. Deviations from the above data can occur in conjunction with process gases depending upon the gas quality and the degree of gas handling.
- Unless otherwise specified the CONTHOS gas analyzer is neither ex-proof nor intrinsically safe in terms of explosion protection.
- The CONTHOS may not be employed for the analysis of ignitable gas-mixtures. The customer must ensure compliance with applicable regulations when using the analyzer with inflammable or toxic gases or when installing within explosion endangered environments.
- The customer must ensure that the sample gas is dry and free of particulates.
Downloads
Downloads 
CONTHOS 3-TCD | Process Thermal Conductivity Gas Analyzer Series
Brochures and Product Data Sheets
Application Questionnaire
Sample Applications
- Iron and Steel production – blast furnace - Process Gas Analyzer
- Heat Treatment and Hardening Process - Hydrogen Process Gas Analyzer
- Water Electrolysis Process - Hydrogen Process Gas Analyzer
- Hydrogen Cooled Generators - TCD Process Gas Analyzer
- Coal Gasification Gas Processing - Process Gas Analyzer
- Air Separation Plant and Bottling - Process Gas Analyzer
- Synthesis Gas - Syngas Processing - Hydrogen Process Gas Analyzer
- High Temperature Applications - Hydrogen Process Gas Analyzer
- Refinery Continuous Catalyst Regeneration - TCD Process Gas Analyzer
Technical specifications subject to change without notice
