Explosion-proof gas calorimeter OHC-800

Support full range of fuel gases such as :

  • Natural Gas
  • e-methane
  • Hydrogen
  • High accuracyOIML R140 class A

    -Natural gas
    -Natural gas + Hydrogen

  • Continuous measurement

    Data updated every 0.25 seconds

  • High-speed response

    T90 within 5 seconds

About OHC-800

  • Improve Combustion efficiency
  • High-speed response / Stable calorific values
  • Low maintenance costs

Address all Gas Calorimeter challenges!

Comparisons of calorimetric solutions
Detection method


Gas chromatography Gas
Combustion type Combustion type
Densimeter Densimeter
Accuracy Excellent
Repeatability: 0.02MJ/m3
Repeatability: +/- 1.0%FS
High heating value: ±1.0% MJ/Nm3
Low heating value: ±1.5%MJ/Nm3
Effect by interference gases i.e.. CO2, N2
Continuous measurement Excellent
Data updated every 0.25 seconds
High-speed response Excellent
T90 within 5 seconds
Analysis time 3-4 minutes
41-60 seconds or less
T90 within 5 seconds
Running cost Excellent
Measurement gas: 0.3L/min
Reference gas: 0.01 L/min(Air/N2)
Sensor replacement: Not Necessary
Measurement gas: 0.3-0.5L/min
Calibration gas: 1.2scf/day
Sensor replacement: every 1 -3 years
Carrier gas (He) : 50L/2years
Measurement gas: 10L/min
Calibration gas: required
Sensor OH: every 1 -3 years
Instrument air: 50L/min
Measurement gas: 0.1-1L/min
Calibration gas: required
Sensor OH: every 2 -5 years
OHC-800 Line image

Why Choose Riken Products

All in one explosion-proof gas calorimeter which features high accuracy, continuous measurement and high-speed response.

Continuous measurement

Measurement data can be updated every 0.25 seconds, a feature which is not possible with gas chromatography. Robust design for all measurement environments eliminates the risk of measurement outages.


Comparison data of OHC-800 and GC measurements of fuel gas containing nitrogen. OHC-800 has the same high accuracy as the gas chromatograph, furthermore OHC-800 will perform continuous measurement, rapid change tracking without affected by N2, which is not able to be observed by GC.

High accuracy

By combining an optical sensor and a sound velocity sensor to perform unique calculations, the system is not affected by interference from gases that do not have heat content, such as N2, CO2, and O2.

The OHC-800 has OIML R140 the highest class “A” approval for natural gas, and a mixed gas of natural gas + hydrogen up to 20vol%.

<What is OIML?>
The OIML is an “international standard-setting body” in the sense of the World Trade Organization's Technical Barriers to Trade Agreement.

Click here and find the downloads for more details about OIML R140 and its certificate.

High accuracy

High-speed response

T90 Fast response time of less than 5 seconds. Responding to sudden changes in calorific value.

Click each item to see the details.

OHC-800 Applications

The OHC-800 has been introduced into various industrial sectors where calorimetric measurement is required, such as oil refining, steel industry, ship building, laboratories, universities, food industry, gas companies, turbine manufacturers, and glass manufacturers.

  • Optimization of air-fuel ratio for turbines and furnaces

    Optimization of air-fuel ratio for turbines and furnaces

    Calorific efficiency brings stability and greater energy output which leads to increased turbine life and furnace efficiency. Therefore leading to lower maintenance and running costs and increased financial returns.

  • Calorific adjustment of natural gas or LNG vaporized gas

    Calorific adjustment of natural gas or LNG vaporized gas

    Cost Reduction of fuel gas and stabilization of quality

  • Calorimetry and composition analysis of steel by-product gas

    Calorimetry and composition analysis of steel by-product gas

    Efficient reuse of steel by-product gas and improvement of the production efficiency by automating the operation of the furnaces properly

  • Calorimetric measurement of petroleum refined by-product gas

    Calorimetric measurement of petroleum refined by-product gas

    Efficient reuse of by-product gas

  • Power to Gas (H2 injectionやMethanation)

    Power to Gas
    (H2 injection and/or Methanation)

    Accurate calorimetry of natural gas containing hydrogen

  • Optimization of calorific values in glass production, pottery production and food production

    Optimization of calorific values in glass production, pottery production and food production

    Stabilization of product quality and improvement of production efficiency

  • Determination of transaction price

    Determination of transaction price

    Real-time calorific value (CV) fiscal metering
    * OIML R140 Class A Approval

  • Methane Number (MN) measurement

    Methane Number (MN) measurement

    Control and prevent engine knocking

  • Combustion optimization at waste incinerators

    Combustion optimization at waste incinerators

    Maintain efficient or accurate combustion

Supported Gas List

  • Natural gas
  • Steel gases (COG,BFG,LDG)
  • LPG
  • Natural gas with Hydrogen
  • Flare gas
  • Methane
  • Natural gas with LPG
  • Boil-off gas
  • E-methane
  • Renewable natural gas
  • Off-gas from refinery
  • Butane
  • Biogas
  • Methanation gas
  • Low calorie gases, and so on
  • Biogas with LPG
  • Hydrogen
  • Hydrogen
  • Biogas
  • Flare Gas
  • Low Calorie Gas
  • e-methane
  • Natural Gas
  • Steel Gas

Any other gases can be accommodated by customizing our sensors or the settings.
Feel free to contact us for more information.


World's first RIKEN OPT-SONIC method
Evaluating the calorific value of fuel gas by measuring the sound speed and the light speed passing through the fuel gas.

Measurement deviation caused by gas interference

The OHC-800 Opt-Sonic gas calorimeter uses two sensors, an optical sensor, and a sonic sensor.

Each of these sensors independently measures calorific value. When measuring fuel gases, interference gases such as N2, CO2, O2, and CO will affect the sensor response in different ways.

Riken Keiki discovered a correlation between these sensor response deviations caused by interference gases.

Applying the opt-sonic calculation means the effects of fuel gas interferences can be negated; ensuring truly accurate and repeatable Calorific Value measurements.

Graph image1

Opt-Sonic calculation explained

Riken Keiki have discovered a correlation between optical and sonic sensors whereby the ratio of measurement deviation remains constant, which is approximately 2.20 regardless of the gas type.

Mathematical formula image

Applying the opt-sonic

Applying the opt-sonic calculation eliminates interference effects, thus giving truly accurate Calorific Value (CV) measurements.

Graph image2

Proud of delivering over 200 units all over the world

We are proud to have delivered more than 200 units of OHC-800 to major engineering companies, gas companies, and turbine manufacturers all over the world.
Utilizing our established overseas network, we are expanding sales to overseas markets.

World MAP

Customer Testimonials

Customer feedback from those already using the OHC-800.

It can help prevent sudden accidental fire.

Basically, OFF gas is used for power generation and boiler fuel, which made calorific values change suddenly due to changes in the operations and eventually the stops might be concerned.
OHC-800 can help prevention of such sudden accidental fire thanks to its feature to measure the calorific values of gases ranging in composition types and their proportions, and catch such sudden changes.
The running cost for OHC-800 is relatively low despite it is basically high in analyzers.

Drastic reduction in the maintenance hours and costs.

High cost of consumables and maintenance has been some troubles in the past, which is caused by measurement of by-product gases in iron making with analyzers and other principles.
By-product gas should be significant equipment because it is used for fuel for power generation and heat source fuel so as to affect the operations.
The maintenance hour and its cost has been enabled to be reduced thanks to the physical sensor (*) which does not require consumables.
(*) Excluding preprocessing filter

We are really satisfied with the measurement accuracy and response speed.

The composition of LNG to be used as fuel for gas turbines coming into Japan has been diversifying year by year, especially the amount of mixed gases. OHC-800 is the best one to measure calorimetry of the gases whose compositions are fluctuated so much, and the measurement with the other calorimeters using measurement of physical quantity instead is also so much fluctuated. We are really satisfied with the measurement accuracy and response speed.

Relief as if a "craftsman" is here.

Calorific control during heat treatment is extremely important for quality at a glass manufacturing site.
OHC-800 is really helpful, because its controllability and monitoring performance both are so good and the response speed is also very high.
We feel like there is “craftsman” who can check color of the flame in the furnace and monitor the calorific value, which can make us feel relief.

Certifications / Approvals

Product Specification

Measuring principle
Opt-Sonic method through measurement of light speed and sound speed
Measuring gas (*1)
CH4 basis Paraffinic Hydrocarbon gases as represented by Natural Gas (*2)
  • (*1) We are capable of measuring many types of gas. Contact us for details.
  • (*2) Total concentration of interference gases such as N2, O2, CO2, CO etc. contained in a target gas is estimated as less than 20%
Measuring targets
Calorific value (Density / WOBBE index selectable)
Measuring range (*3)
Calorific value : 25.00 - 50.00 MJ/m3 (Gross, 0 degree C, 101.325kPa converted)
Density : 0.500~1.500 MJ/m3 (Specific gravity converted)
  • (*3) Contact RIKEN KEIKI for the other measuring ranges
Measuring method
Constant-flow-rate gas introduction using external sampling devices
Full-dot LCD (with backlight), 3 color LED lamp
External Output
4-20 mA DC (isolated, source current type) maximum load resistance of 300 Ω / RS-485 communication
Failure alarm
Low flow, Sensor unit abnormality, Low light amount
Failure alarm display
Lamp (red) / Content indication on LCD
Failure alarm contact (*4)
No-voltage contact 1a or 1b De-energize (Energize when alarming) or Energize (De-energize when alarming)
Contact capacity of 2 A, 30 VDC (resistance load)
  • (*4) Contact setting is adjustable
Self-diagnostic function
Self-diagnostic display
FUNCTION CHECK, OUT OF SPECIFICATION : Lamp (orange) / Content indication on LCD
MAINTENANCE REQUIRED : Lamp (green) / Content indication on LCD
Self-diagnostic contact
FUNCTION CHECK, OUT OF SPECIFICATION : No-voltage contact 1a or 1b
De-energize (Energize when alarming) or Energize (De-energize when alarming) Contact capacity of 2 A, 30 VDC (resistance load)
MAINTENANCE REQUIRED : SSR contact, contact capacity of 20 W, 240 VAC (resistance load)
  • (*4) Contact setting is adjustable
Power supply
100 - 240 VAC ±10%, 50/60 Hz, max. 18 VA or 24 VDC ±10%, max.
5 W (The setting can be changed to either the AC or DC)
Ingress Protection level
Equivalent to IP66 and IP67
Operation temperature
-20 to+60 ℃ (-4 to +140 ℉)(ATEX / IECEx)/ -20 to+57 ℃ (-4 to +134.6 ℉)(Japan EX)
Operation humidity
95%RH or less (no condensing)
Outer dimensions / Weight
Approx. 286 (W) x 453 (H) x 150 (D) mm / Approx. 23 kg (50.7 lbs)
Explosion-proof structure
Flame-proof enclosures (Explosion-proof class: ExdⅡB+H2 T4 <Japan EX>/Ⅱ2GExdⅡB+H2T4 <ATEX/IECEx>)

About us

Since our company was founded in 1939 under the umbrella conglomerate of RIKEN, our management philosophy has been to create safe working environments. Our science and technology research laboratories have developed industrial gas detection warning devices, specialising in monitoring harmful gases in the work environment, as well as for explosion prevention from combustible gases.

Without compromise, we continue to challenge ourselves to be technological leaders, developing and manufacturing a wide range of industrial gas detection systems and monitors. From large-scale gas detecting alarm systems to small-sized personal gas monitors for safety protection; used in many industries including semiconductor and LCD plants, petroleum complexes, steelworks, various tankers, oil storage stations, underground gas facilities, and volcanoes.

Experts in gas detection for over 80 years image

Experts in gas detection for over 80 years

The “RIKEN Gas Detector” utilising the principle of light wave interference, was exhibited at the 1937 Paris World Exposition. Its subsequent use greatly contributed to the prevention of accidents in coal mines where many fatalities were prevalent at the time.
On the 15th March 2019 we celebrated our 80th anniversary. Supported by our history and tradition we shall further improve long established technology, and continue to innovative. Developing reliable quality products in response to the diverse needs of industry.

International Network image

International Network

We have established a mature global network of affiliated companies and distributors across all the world, so our products can be locally supported with confidence.

Affiliated company Distributor
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