Thermatel® TG1/TG2 provides a two-wire, intrinsically safe circuit between the probe and remote din rail enclosure. The flow/level/interface switches provide a new level of performance and reliability not found in previous switches. Continuous diagnostics with fault indication, narrow hysteresis and fast response time make the TG1/TG2 the latest in thermal dispersion switch technology.

Operating Principle

The THERMATEL sensor consists of two RTD elements. One is the reference and the second is heated to a temperature above the process temperature. The electronics detect the temperature difference between the two elements. The temperature difference is greatest in air, then decreases when cooling occurs due to a change in media. An increase in the flow rate further decreases the temperature difference.
The set point is adjusted for the switch to alarm at the desired temperature difference. Once the set point is reached, the relay will change state.


- Low flow detection
- High temperature operation
- High viscosity
- Coating media
- Interface detection



- Two-wire intrinsically safe design with integral barrier
- LED indication provides continuous indication of flow rate relative to switch point
- 24 VDC input power
- Output: + 2 Amp SPDT alarm relay with goldflash contacts
+ mA output signal for diagnostic fault indication per NAMUR NE43
- High/Low fail safe selection
- Adjustable set point and time delay


- Standard twin tip sensor:
+ Corrosive resistant materials
+ Pressures to 3000 psig (205 bar)
- Standard spherical tip sensor:
+ General purpose service
+ Stainless steel only
- High temperature sensor:
+ Temperatures up to +850° F (+450° C)
+ Pressures up to 6000 psi (413 bar)
- Low flow body with 1/4" and 1/2" connections


- Low flow body for very low flow rate detection
- Hot tap retractable probe
- Hygienic design
- NACE construction
- Low flow body for very low flow detection


+ Product Catalog
+ Instruction & Operating Manual