Passives

Resistor features built-in climate control

12th August 2014
Siobhan O'Gorman
0

A resistor with built-in climate control has been introduced by Vishay Foil Resistors (VFR). The bulk metal foil RTD simulator resistor is designed to simulate PT-100 and PT-1000 RTD outputs for the calibration of RTD instruments. The resistor, the company claim, provides a faster, easier and less expensive alternative to decade boxes and electronic simulators for the calibration of a range of applications including transmitters.

The device features a low nominal TCR of ±1ppm/°C from -55 to +125°C, +25°C ref., and load-life stability of ±0.005% after 2,000 hours of rated power at +70°C. Each resistor comes with certification and features temperature simulation from -200 to +850°C.

Power ratings to 0.6W at +70 °C, along with a maximum working voltage of 300V are offered by the RTD Simulator. A resistance range from 10Ω to 5kΩ, with tight resistance tolerance to ±0.005% (50ppm), is also featured. Any ohmic value within this range, to six digits, is available with no additional cost or lead time effect. 

With a non-inductive (<0.08 μH), non-capacitive design, the resistor offers a rise time of 1.0ns with effectively no ringing and thermal EMF of 0.05μV/°C. This also results in voltage coefficient of <0.1ppm/V and current noise of 0.010μVRMS/V of applied voltage (<-40 dB). The resistor withstands ESD spikes to at least 25kV and is available with both lead (Pb)-free and tin/lead alloy terminal finishes.

"The climate control capabilities of the RTD Simulator are provided by the inherently low absolute TCR of Bulk Metal Foil resistors, which itself results from two predictable and opposing physical phenomena within the composite structure of the resistive alloy and its substrate," said Yuval Hernik, Senior Director of Application Engineering, VFR. "The first is that the resistance of the alloy increases with the temperature. The second is that the coefficient of thermal expansion of the alloy and substrate are different, resulting in a compressive force on the alloy when the temperature increases and a consequent decrease of the foil resistance. The two effects occur simultaneously, resulting in an unusually low predictable, repeatable, and controllable TCR."

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