FOTEMP-Trafo (No longer available-see FOTEMP-T2 for new applications)

Fiber Optic Thermometer

The DIN rail mount FOTEMP-TRAFO is an 8-channel fiber optic thermometer, which is ideal for temperature monitoring of hot spots in transformers and other industrial processes. This multi-channel instrument together with the TSTrafo fiber optic temperature probes enable accurate and precise measurements of transformer windings. By direct installation of the sensors in the windings, real-time monitoring is possible.

The fiber optic thermometer FOTEMP-TRAFO is available with 1-8 measurement channels. The compact unit size and the height-adjustable DIN-rail-clip provides an easy installation in the cabinet. A wide selection of interfaces makes communication even easier. All models are supplied with a built-in USB interface for ease of configuration with the supplied FOTEMP-ASSISTANT software. The second interface can be RS-232, RS485/Modbus RTU or Ethernet/Modbus TCP. An update rate of 250ms per channel allows for fast response.

The fiber optic temperature probes consist of a length of large core fiber onto which a GaAs crystal has been mounted at the tip which makes the probe entirely passive. Starting at 850nm, GaAs becomes optically translucent for which the band gap position is temperature dependent. The FOTEMP unit contains a light source and a device for spectral detection of the band gap.

Optocon fiber optic sensors offer complete immunity to RF and microwave radiation with high temperature operating capability, intrinsic safety, and non-invasive use. The probes are also designed to withstand harsh and corrosive environments.


Number of channels 8
Power supply 24V (DIN rail mount unit provided)
Measuring range —200°C to +300°C
Accuracy +/—0.2°C (σ)
Resolution 0.1°C
Sampling rate/channel 250ms (2s update rate for 8 channels)
Analog output 0-10V or 4-20mA
Interfaces Standard: USB (ASCII Protocol)

Options: RS232 (ASCII) , RS485/Modbus RTU, Ethernet/Modbus TCP

Protocol ASCII and Modbus software protocol available for

custom programmming applications

Data logging Supplied with FOTEMP-Assistant data logging software. Excel file compatibility.
Optical Interface ST, compatible with all TS series fiber optic temperature probes
Temperature Storage: -20°C to +70°C

Operating: -20°C to +60°C

Dimensions/Weight/IP 240 x 180 x 75 mm, 1.2 kg, IP54
Material PC-ABS / Aluminium casting RAL 9003
Calibrations Standard: -40°C to +300°C

C Extended: -200°C to +300°C

Calibration Interval Under normal use, the instrument does not require recalibration. When sensors and cables are changed, a One-Point Calibration is required. Recommended cal interval is 12 months for ISO quality systems.

Specifications subject to change without notice


  • Robust & durable DIN rail mount case
  • 1-8 measuring channels
  • Measuring range: —200°C to +300°C
  • High accuracy: +/—0.2°C
  • Status LED
  • 0-10V or 4-20mA analog output option
  • 1-8 relay option, freely assignable to any channel
  • Built-in USB interfaces
  • 2nd Interface Option: RS232, RS485/Modbus RTU, or Ethernet/Modbus TCP
  • FOTEMP-ASSISTANT configuration and data logging software provided


  • Monitoring of “Hot-Spots” inside high voltage transformers, capacitors, and alternators
  • Temperature measurement on high voltage distribution power lines such as for electric trains
  • Temperature measurement in gas isolated switchgear, power breakers, and power factor adjustment capacitors
  • Economical multichannel solution




Call +1-805-389-6600 or email

Ordering Information

FOTEMP8-TRAFO-X-Y-Z Fiber Optic DIN Rail Mount Signal Conditioner
where X=Interface: P0=USB+RS232, P1=USB+RS485/ModbusRTU, P2=USB+Ethernet/ModbusTCP
where Y=Analog Output Option: V=0-10V, M=4-20mA
where X=Calibration Option/Measurement Range:: (Blank)=Standard -40°C to +300°C, Extended C Option=-200°C to +300°C

Quick Ship Configurations

FOTEMP8-TRAFO-P0-M 8 Channels, USB+RS232, 4-20mA, Calibration=-40°C to +300°C
FOTEMP8-TRAFO-P1-M 8 Channels, USB+RS485/ModbusRTU, 4-20mA, Calibration=-40°C to +300°C
FOTEMP8-TRAFO-P2-M 8 Channels, USB+Ethernet/ModbusTCP, 4-20mA, Calibration=-40°C to +300°C
TS2 Sensors, General Purpose TS2-02 or TS2-06
TS3 Sensors, General Purpose, Rigid Tip TS3-10MM-02 or TS3-10MM-06
TS4 Sensors, Harsh TS4-02 or TS4-06
TS5 Sensors, Medical TS5-20MM-02 or TS5-20MM-06
General Purpose FO Extension Cables (meters) DIST-C320-03 or -05 or -10