XMTCPanametrics Thermal
Conductivity Binary
Gas TransmitterApplications
A thermal conductivity gas transmitter for use
in the following industries and applications:
Metals industry
H2 in N2 atmosphere in metal heat-treating furnaces
Electric power industry
H2 in cooling systems for generators
Petroleum industry
H2 in hydrocarbon streams
Chemical industry• H2 in ammonia synthesis gas• H2 in methanol synthesis gas• H2 in chlorine plants
Methane industry• CO2 in methane
Landfill/biogas industry• CO2 in biogas• CH4 in biogas
Gas production industry
Purity monitoring of argon, hydrogen, nitrogen and helium
Food Industry
CO2 in fermentation processesFeatures• Ultra-stable glass-coated thermistors• Single or dual gas push-button calibration• PC interface package for digital output• Type IP66/4X construction• ATEX, IECEx, FM and CSA certified for Zone Iand Division 1 hazardous areas
The microprocessor-based XMTC is a compact, rugged,
online thermal conductivity transmitter that measures theconcentration of binary gas mixtures including hydrogen,carbon dioxide, methane, helium and many others. The analyzer
also combines computer enhanced signal measurement with
fast-response software, real-time error detection and digitalcommunication via an RS232 or RS485 interface.

Theory of operation
Two ultrastable, precision glass-coated thermistors are used—
one in contact with the sample gas and the other in contact
with the reference gas (such as air in a sealed chamber). The
thermistors are mounted so that they are in close proximity
to the stainless steel (or Hastelloy®) walls of the samplechamber. The entire transmitter is temperature-controlled,
and the thermistors are heated to an elevated temperature
in a constant-current Wheatstone bridge. The thermistors
lose heat to the walls of the sample chamber at a rate that is
proportional to the thermal conductivity of the gas surrounding
them. Thus, each thermistor will reach a different equilibrium
temperature. The temperature difference between the twothermistors is detected in the Wheatstone bridge, and theresulting bridge voltage is amplified and converted to a linear 4
to 20 mA output proportional to the concentration of one of theconstituents of the binary or pseudo binary gas mixture.

Minimal calibration and service

Choosing the reference gasThe XMTC is the most stable thermal conductivity analyzer
on the market today. The rugged XMTC measuring cell resists
contamination and remains insensitive to flow variations. Since
the design uses no moving parts, the transmitter can easily
withstand the shock, vibration and harsh environment foundin many industrial applications. If the transmitter requires
maintenance, its modular construction permits fast and easy
servicing. Users can field-calibrate it quickly and replace theplug-in measuring cell with a precalibrated spare in minutes.

The simple two-port version can be selected formeasurement of zero-based gas mixtures using the sealed
reference gas (air). There is a four-port version for improved
performance using a specific flowing reference gas.

XMTC specifications
Performance

Accuracy: ±2% of span
Linearity: ±1% of span

Sample system
A sample system is mandatory for use with the XMTC. The
design of the sample system will depend on the conditions of
the sample gas and the requirements of the application. In
general, a sample system must deliver a clean, representative
sample to the XMTC at a temperature, pressure and flow ratethat are within acceptable limits. Standard XMTC sample
conditions are: a temperature of less than 122°F (50°C) fora cell operating temperature of 131°F (55°C) with a flow rateof 0.5 SCFH (250 cc/min) at atmospheric pressure. A higher
temperature option is available.
Panametrics offers sample systems for a wide variety ofapplications. For assistance in designing your own sample
system, please consult our application engineering team.

Relative thermal conductivities
of common cases

Repeatability: ±0.5% of span
Zero Stability: ±0.5% of span per week
Span Stability: ±0.5% of span per week
Response Time: 20 seconds for 90% step change

Measurement Ranges• 0% to 2%• 0% to 5%• 0% to 10%• 0% to 25%• 0% to 50%• 0% to 100%
• 50% to 100%
• 80% to 100%
• 90% to 100%
• 95% to 100%
• 98% to 100%

Measurement Gases (Typical)• H2 in N2, air, O2 or CO2• He in N2 or air• CO2 in N2 or air• SO2 in air• Argon in N2 or air• H2/CO2/air for hydrogen-cooled generators
Note: Graph is relative thermal conductivity at 212°F (100°C)
GasFormula

ChemicalGas

FormulaChemicalAcetylene

0.90

C2H2

Helium

5.53

HeAir

1.00

N2/O2

n-Heptane

0.58

C7H16

Argon

0.67

Arn-Hexane

0.66

C6H14

n-Butane

0.74

C4H10

Hydrogen

6.80

H2CarbonDioxide

0.70

CO2Methane

1.45

CH4

Chlorine

0.34

Cl2

MethylChloride

0.53

CH3Cl

Ethylene
Alcohol

0.64

C2H5OH4

Neon

1.84

Ne

Ethylene

0.98

C2H4

n-Pentane

0.70

C5H12

Ethylene
Oxide

0.62

C2H40

SulfurDioxide

0.38

SO2Freon-110.37

CCl3F

Water
Vapor

0.77

H20

Required Sample Flow Rate
0.1 to 4.0 SCFH (10 to 2,000 cc/min);
0.5 SCFH (250 cc/min) nominal
Required Flow Rate for Optional Reference Gas
0.01 to 4.0 SCFH (5 to 2,000 cc/min);
0.5 SCFH (250 cc/min) nominal

Functional
Analog Output
4 to 20 mA isolated, 800 Ω maximum load, field-programmable
Power
24 VDC ±2 VDC, 1.2 A maximum
Temperature• Standard: 131°F (55°C)• Optional: 158°F (70°C)

* Weatherproof** Explosion-proof

Order and calibration information

6.10 [155]3/4” NPTF

5.71 [145]

XMTC Thermal Conductivity Transmitter
Measuring Cell Package

2.76 [70]4.13 [105]*or
5.07 [129]**

1

Weatherproof two port sealed reference CPVC cell

3

Weatherproof, four-port, flowing reference gas, CPVC cell

5

Weatherproof enclosure, two-port, sealed reference gas,
FEP-coated aluminum cell

2XMTCtransmitter

8.66 [220]9.54 [242.3]* or 10.48 [266.2]**

6.10 [155]60.39 [10]diameter

0.68 [17.3]

1.16 [29.5]

40.47 [11.9]

Optional flame
arrestors for
explosion-proof
units only

24 VDC / 1 Amp 1
Return 2
4 to 20 mA+ 3
4 to 20 mA- 4
Red_RX 1
White_TX 2
Ground 3

1/4” NPTF

Explosion-proof two port sealed reference CPVC cell
Explosion-proof enclosure, four-port, flowing reference gas, CPVC cell

Explosion-proof, two-port, sealed reference gas, FEP-coatedaluminum cellW

No enclosure, two-port, sealed reference gas, FEP-coatedaluminum cell (spare)X

No enclosure, two-port, sealed reference CPVC cell (spare)Y

No Enclosure, four port , sealed reference CPVC cell (spare)
CE Compliance
2 4 to 20 mA

C CE Compliant

Calibration Label for Explosion-proof Options

3.27 [83]1Note: All dimensions = inches [mm]T6 Rating for Ambient Temperatures Up to 65°C
Materials

4.34 [110.3]

1316 stainless steel3316 Stainless Steel / Chemraz O Rings

2

XMTC specifications
PhysicalSensor wetted materials• Standard: 316 stainless steel, glass and Viton® O-rings• Optional: Hastelloy C276 and Chemraz® O-rings
Dimensions• Weatherproof unit (h x diameter): 9.53 x 5.71 in. (242 x 145 mm)• Explosion-proof unit (h x diameter): 10.47 x 5.7 in. (266 x 145 mm)
Weight• 9.5 lb (4.3 kg)

Environmental• Weatherproof: Class I Div. 1 Groups A, B, C & D
Class II, III Div. 1 Groups E, F & G
Tamb 65°C T5 Type 4X• Flameproof:
IECEX/ATEX
II 2 G Ex d IIC T6 Gb
IP66 -20°C < Tamb < +65°C
All conduit entries 3/4” NPT• CE: EMC 2004/108/EC
European compliance
Complies with EMC Directive 2004/108/EEC
NEC/CSA• Class I, Div I, Groups A, B, C and D;• Class II, Div I, Groups E, F and G;• Class III; Enclosure Type 4X• FMCopyright 2023 Baker Hughes Company. All rights reserved.
(04/2023)__ [Use this number to order product]

XMTC Calibration Specifications
Cell Range
20% to 2%

80% to 100%40% to 10%

B80% to 100%

367Connections• 3/4 in NPTF (electrical conduit)• 1/4 in NPTF (sample inlet/outlet and optionalreference inlet/outlet)

BHCS38653		

XMTC – __ __ __Hastelloy/C276 /Chemraz O Rings

0% to 5%

A0% to 25%

C0% to 50%

234567S

50% to 100%

D98% to 100%

SSpecial

ECalibration Gases
190% to 100%95% to 100%

H2 in N2

CO2 in N2 (minimum range 0% to 20% CO2)

CO2 in air (minimum range 0% to 20% CO2)

He in N2

He in airCalibration for hydrogen-cooled generators,
H2/CO2/air

CH4 in CO2 (min range 0% to 10% CH4)

Other, please specify

Temperature Control Set Point
1131°F (55°C), suitable for ambient temperatures

2158°F (70°C), suitable for ambient temperatures

S

up to 122°F (50°C)

up to 149°F (65°C)
SpecialCalibration Special0none2Special

1

Ambient temperature compensation

XMTC-Cal __ __ __ __ [Use this number to order product]

Note: Binary or pseudobinary gas composition must total 100%.

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