Thermatel® TD1/TD2 thermal dispersion switches

The Thermatel® Model TD1/TD2 switch is utilized in flow, level and interface applications. The TD1/TD2 is popular for pump protection, specifically low flow detection with the unique spherical tip design, to prevent pumps from running dry. Continuous diagnostics with fault indication, temperature compensation and fast response time make the TD1/TD2 the latest in thermal dispersion technology.

Technology

Thermal dispersion switch

The thermal switches are based on convective heat transfer.  One sensor is at the process temperature and the other is being heated by a constant power.  As the flow rate increases, the temperature difference between the sensors decreases.  A set point is established so when that specific temperature difference is reached the relay changes state.  This can be on either increasing or decreasing flow or flow/no flow.  When used in a level or interface application it is primarily the thermal conductivity of the fluid that will provide the difference in heat transfer.

Thermal Dispersion Switch
  • Features
  • Applications
  • Operating principle
  • Approvals
  • Downloads

  • Temperature compensated to provide repeatable alarm under varying process temperatures
  • Continuous diagnostics detect sensor fault
  • Non-linear mA output signal can be used for trending, diagnostics and repeatable flow/level indication
  • Detects minimum flow or presence / absence of flow
  • Excellent low flow sensitivity
  • Simple calibration / installation

Options

  • Hot tap retractable probe
  • Hygienic design
  • NACE construction
  • Window to view alarm status
  • Integral or remote electronics
  • Flow body for very low flow detection

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.

ATEX Ex d, Ex d+ib
CCOE Ex d
CSA XP, NI
FM XP, NI
EAC (GOST)
Ex d
IEC
Ex d, Ex d+ib
Inmetro
Ex d, Ex d+ib
Korea
Ex d
SIL
SIL 1 (1oo1)

Other approvals are available. Consult factory for more details.

  • Application Questionnaire
    • Thermatel® TD1 - TD2 Calibration Sheet
  • Approvals and Certificates
    • ATEX Ex d Ib Certificate Thermatel® TD1 - TD2
    • ATEX Ex d Ib Certificate Thermatel® TD1 - TD2 - 1
    • Canadian Certificate Thermatel® TD1 And TD2 XP NI
    • FM Certificate Thermatel® TD1 And TD2 XP NI
    • FMEDA Report Thermatel® TD1 - TD2
    • IECEx d Certificate Thermatel® TD1 - TD2
  • Instruction Manuals
    • USA Thermatel® Model TD1 - TD2 Switch I&O Manual
    • English Thermatel® Model TD1 - TD2 Switch I&O Manual
    • French Thermatel® Model TD1 - TD2 Switch I&O Manual
    • German Thermatel® Model TD1 - TD2 Switch I&O Manual
    • Italian Thermatel® Model TD1 - TD2 Switch I&O Manual
  • Product Catalogs
    • USA Thermatel® TD1 - TD2 Product Catalog
    • English Thermatel® TD1 - TD2 Product Catalog
    • French Thermatel® TD1 - TD2 Product Catalog
    • German Thermatel® TD1 - TD2 Product Catalog
    • Italian Thermatel® TD1 - TD2 Product Catalog

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