The analog output parameters comprise the scale factor and the offset. The scale factor corresponds to the physical unit per Volt (unit/V) output by the system, while the offset corresponds to the physical value at which the user wants the analog output to be at zero volt. For example, with a scale factor set to 10 °C / V and the offset set to 5 °C, the temperature as a function of the analog output voltage is given by:
Temperature = [Voltage output] x 10 °C / V + 5 °C
The default value of the scale factor is 50 °C / V (or its equivalent in °F) and the default value of the offset is 0 °C (or its equivalent in °F).
During a No Signal condition, constant values are output as follows: analog output value = 0 Volt, RS-232 serial ports = 65 536.0.
For more details, please see the complete FOTS100 User Manual, available under the Support tab.
Use with high-accuracy, fiber optic temperature probes for use in MRI (separate purchase):
- The Polyimide round tubing protects the sensing element its flexibility and rigidity provide excellent pushability.
Surface Temp Probe: sensor 1 mm OD, PFA tubing 0.9 mm OD – TSD181 8 m
- cable sheath rated up to 85 °C.The glass tube at the end of the probe provides a robust protection over the sensing element as well as a firm connection from sensor to cable.
Note: FOTS100, TSD180, and TSD181 are suitable for MR field strength of 3T and lower; see FOTS200 with TSD380 and TSD381 transducers for high field strength MRI applications.
Comparison of FOTS Signal Conditioners available from BIOPAC:
When exposed to strong magnetic field, the GaAs sensor used with the FOTS100 will see an artificial shift in temperature :
Magnetic field Shift in T° (approximately)
This shift does not depend on field orientation and is very reproducible in a given setup, hence it can be easily factored out by the user.
The values at field strength come from the following article: Buchenberg, W.B., Dadakova, T., Groebner, J., Bock, M. and Jung, B. (2015), Comparison of two fiber‐optical temperature measurement systems in magnetic fields up to 9.4 Tesla. Magn. Reson. Med., 73: 2047-2051. doi:10.1002/mrm.25314
The TSD380 series sensor probes associated with the FOTS200 readout unit have an optical sensing element that is insensitive to magnetic field, hence, there is no maximum magnetic field specification, which is a nice advantage in high-field MRI applications.
However this technology has some disadvantages: it is more expensive; the probe cannot be made to a diameter smaller than 1.2 mmm O.D.
For more details, please see the complete FOTS100 User Manual,
available under the Support tab.