Overview of T-mass 65 (65I/65F) Analog Flow Velocity Measurement
T-mass 65 is a thermal mass flowmeter series launched by Endress+Hauser, including two installation types: 65I (insertion type) and 65F (flanged type). This series of instruments is based on the thermal diffusion principle and directly measures gas mass flow without additional temperature and pressure compensation.
In analog flow velocity measurement scenarios, T-mass 65 can output a 4-20mA analog signal, reflecting gas flow velocity changes in the pipeline in real time. Its high turndown ratio and low flow velocity sensitivity make it outstanding in industrial gas measurement such as compressed air, natural gas, and biogas.
Core Measurement Principle and Signal Output
Thermal Diffusion Measurement Principle
T-mass 65 uses two platinum resistance temperature sensors: one for heating and one for measuring the medium temperature. When gas flows through the heated sensor, it carries away heat, and the heating power is proportional to the mass flow rate.
By precisely controlling the heating power and measuring the temperature difference, the instrument can directly calculate the gas mass flow under standard conditions. This principle has extremely high sensitivity to low flow velocity and small flow rates.
Analog Signal Output Characteristics
- 4-20mA analog output: Corresponds to the set flow range, linearly outputs flow velocity or mass flow.
- Pulse/frequency output: Optional, used for total accumulation or high-precision measurement.
- HART communication: Supports remote configuration and diagnostics, compatible with mainstream control systems.
Selection Comparison Between 65I and 65F
According to pipeline size and installation conditions, T-mass 65 provides two structures: insertion type and flanged type. The table below compares key parameters for engineering selection.
| Parameter | 65I (Insertion Type) | 65F (Flanged Type) |
|---|---|---|
| Applicable pipe diameter | DN80 ~ DN1500 | DN15 ~ DN300 |
| Installation method | Insertion type, with ball valve for online removal and installation | Flanged installation, fixed type |
| Accuracy | ±1.5% o.r. + 0.5% F.S. | ±1.0% o.r. + 0.5% F.S. |
| Turndown ratio | 100:1 | 100:1 |
| Typical applications | Large-diameter pipelines, compressed air, flue gas | Small-diameter gas, natural gas, biogas |
Key Points for Installation and Commissioning of Analog Flow Velocity Measurement
Installation Specifications
- Ensure upstream and downstream straight pipe lengths: 15D upstream, 5D downstream (D is the pipe inner diameter).
- The sensor insertion depth should be at the point of maximum flow velocity in the center of the pipeline to avoid the influence of the pipe wall boundary layer.
- For the 65I insertion type, a ball valve is required for installation and removal under pressure.
- Avoid installation in pipe sections with strong vibration or severe temperature fluctuations.
Commissioning Steps
- Power on and preheat for 30 minutes to allow the sensor to reach thermal equilibrium.
- Set the pipe inner diameter, gas type, and full-scale flow via HART or local keys.
- Perform zero calibration under no-flow conditions to eliminate the influence of installation stress.
- Introduce gas with a known flow rate to verify the linearity of the 4-20mA output.
Typical Applications and Selection Recommendations
T-mass 65 is widely used in fields such as compressed air measurement, natural gas trade settlement, biogas power generation, and flue gas emission monitoring. Its analog flow velocity output can be directly connected to PLC or DCS for real-time monitoring and energy consumption analysis.
- For large-diameter low-pressure gas, prefer the 65I insertion type, which is low-cost and flexible to install.
- For small-diameter high-pressure gas, the 65F flanged type is recommended, with higher accuracy and reliable sealing.
- If the medium contains dust or condensate, filtration or drying devices must be added to avoid sensor contamination.
When purchasing, please provide pipe size, gas composition, flow range, working pressure, and temperature so that the manufacturer can accurately select the model and calibrate the analog output range.