Barrettor vs Thermistor-difference between Barrettor and Thermistor
Power measurements at microwave frequencies are generally done by thermal sensitive devices. These devices utilize heat generated by the microwave energy when E-M wave fall on it. This page on barrettor vs thermistor describes difference between barretor and thermistor used for power measurement at microwave frequencies.
The Thermistor is a small semiconductor bead with connecting wires as shown in the figure. It's resistance decreases with temperature. The bead material used for thermistor manufacturing is a mixture of manganese and nickel oxides with copper dust.
The Barrettor is a short piece of fine wire. It is made of platinum with silver coated. The resistance of barrettor increases with the temperature as shown in the figure.
Following are the basic difference between barrettor and thermistor devices.
• Barrettor has low thermal time constant (i.e. 100 to 300 µs), while thermistor has larger time constant.
• Barrettor operates at high temperature. Hence not suitable to use at ambient temperature as it does not affect operation of barrettor. Thermistor operates at low temperature, hence it is sensitive to ambient temperature.
• Barrettor is not suitable for broadband system.
• Barrettor has poor detector sensitivity about 5.2 Ohm/mWatt while thermistor has high detector sensitivity about 60 Ohm/mWatt. Because of this reason thermistor is more useful at low power measurement.
Refer thermistor page for thermistor types viz. NTC and PTC and thermistor manufacturers.