Tokyo Keiso TH Series Thermal Gas Flowmeter (TH-1100, TH-3200)

Thermal flowmeter family for gas velocity and mass flow

The Tokyo Keiso TH series is a family of thermal flowmeters for gas flow. A heated metal tubule in the gas path loses heat in proportion to the product of density and velocity, and the instrument holds the temperature difference constant while measuring the supplied voltage and current. Tokyo Keiso states that the principle covers very slow to high velocities, with measurement possible in practice from about 0.5 m/s, and that it is little affected by pressure or gas-temperature fluctuation.

The catalogue combines several detectors with several converters. Mass flow is obtained by adding gas temperature compensation, and for gases the physical properties are specified instead of calibrating on each gas. The gas must be dry and free of dust, mist or corrosive components such as chlorine, acids or sulphur. Typical uses listed are semiconductor and medical oxygen supply, air conditioning, utility gas lines, combustion gas, low-pressure low-velocity lines, incineration and power plants.

Technical specifications

This family page follows Tokyo Keiso technical guidance TG-F2124-E04 (5th edition, January 2025). The sensor list below shows each detector type.

Choosing a detector

Pick the detector from the line: TH-1100 or TH-1400 for insertion into larger pipes or square ducts at low cost, TH-1200 where a flanged spool fits the pipework, TH-1700 for pipes 15 to 50 mm, TH-1800 where there is no room for a long straight run, and TH-3200 or the SP variants for hot or dirty gas. Each detector has its own model code for pipe size, sensor material, process connection, length and special treatments such as electrolytic-polished (EP) or BA grade, a thermometer tap and a terminal box instead of a connector.

Flow range tables for many pipe sizes and gases are included in the catalogue, so a size can be checked against the actual normal-condition flow before ordering.

What to confirm before ordering

• Gas composition and cleanliness: dry, non-corrosive gas only; use a purge version for dust.
• Pipe or duct dimensions, gas temperature, and available straight run.
• Converter type, depending on required outputs, temperature compensation and mounting.
• Which single detector model you need. This page covers the series; the catalogue lists sensor codes and dimensions for each one.

Where the TH-SERIES thermal flowmeter is used

• Oxygen supply lines
• Air conditioning systems
• Utility gas lines
• Combustion gas lines
• Incineration and power plants

Selection checklist for the TH-SERIES thermal flowmeter

• Gas type and condition
• Pipe size
• Flow velocity range
• Gas temperature
• Detector type
• Converter type
• Flange or screw ends
• Dust or purge need

Installation, commissioning and maintenance notes for the TH-SERIES thermal flowmeter

Fit the detector in a straight run of pipe with the insertion depth set from the datasheet. Wire the converter and check the gas settings. Inspect the detector tip at regular intervals so that it stays clean.

Requesting a quotation for the TH-SERIES thermal flowmeter

Please send the gas, the pipe size, the velocity range and the gas temperature. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

TH-SERIES meter type

It is a family of thermal flowmeters for gas.

TH-SERIES maker

It is made by Tokyo Keiso.

TH-SERIES measuring principle

A heated metal tubule in the gas path loses heat as the gas flows.

TH-SERIES heat loss

The heat loss depends on the product of density and velocity.

TH-SERIES constant difference

The instrument holds the temperature difference constant.

TH-SERIES measured values

It measures the supplied voltage and current.

TH-SERIES low velocity

Measurement is possible from about 0.5 m/s.

TH-SERIES mass flow

Gas temperature compensation gives mass flow.

TH-SERIES gas properties

Gas properties are specified instead of calibrating on each gas.

TH-SERIES gas condition

The gas must be dry and free of dust and mist.

TH-SERIES corrosive gas

The gas must also be free of chlorine, acids and sulphur.

TH-SERIES TH-1100 detector

The TH-1100 is an insertion detector for pipes of 50 to 1500 mm.

TH-SERIES TH-1200 detector

The TH-1200 is a flange-ended detector for pipes of 50 to 150 mm.

TH-SERIES TH-1400 detector

The TH-1400 is a variable-length insertion detector for flow profile checks.

TH-SERIES TH-1700 detector

The TH-1700 is a small flange-ended detector for pipes of 15 to 50 mm.

TH-SERIES TH-1800 detector

The TH-1800 has flange or screw ends and a built-in straightener.

TH-SERIES TH-3200 detector

The TH-3200 is a high-temperature insertion version for pipes of 65 to 1500 mm.

TH-SERIES TH-3200 temperature

The TH-3200 covers 20 to 550 degrees C.

TH-SERIES TH-3200 converter

The TH-3200 is used with the TRX-600 converter.

TH-SERIES purge versions

The SP versions have a purge function for dusty gas.

TH-SERIES velocity range

Air ranges start at 0 to 0.5 m/s for most detectors.

TH-SERIES maximum velocity

The TH-1100 span reaches 0 to 130 m/s.

TH-SERIES guidance document

The family page follows Tokyo Keiso technical guidance TG-F2124-E04.

Flowmeter records for the TH-SERIES

Record the gas, the detector type and the date of each inspection.

Choosing the right TH-SERIES detector

Choose the detector from the pipe size, the gas temperature and the dust level.

Documents and quotation

The Tokyo Keiso TH series catalogue (all detectors, converters, model codes and flow range tables) is attached to this page as a PDF. Send us the gas, line size, temperature and the detector and converter you prefer, and we will quote against the catalogue codes. Seven Star LLC is an independent supplier in Muscat; price and lead time are confirmed per RFQ. Related range: flowmeters and the ABB SensyMaster FMT200 thermal mass flowmeter.