MF5A-3 Series epoxy coating temperature thermistor small type radial leaded NTC thermal resistor, with its small bead size , bare or insulated DIP lead, wide resistance range from 1K ohm to 2M ohm, it is extensively used for wide sensing temperature range from -50'C to 150'C . Under extreme condition , it can be specially made for larger range -80'C to 200'C . Focussens have full range of resistance parameters in MF5A-3 series , among the range 1K ohm 3540 , 2K ohms 3450 , 2.795K ohms 4100 etc.is welcomly used in automobile HVACR, coolant system .
RTD (Resistance Temperature Detector) is a sensor whose resistance changes as its temperature changes. The resistance increases as the temperature of the sensor increases. The resistance vs temperature relationship is well known and is repeatable over time. An RTD is a passive device. It does not produce an output on its own. External electronic devices are used to measure the resistance of the sensor by passing a small electrical current through the sensor to generate a voltage. Typically 1 mA or less measuring current, 5 mA maximum without the risk of self-heating.
This sensor is essentially a reed switch, encased in an ABS plastic shell. Normally the reed is 'open' (no connection between the two wires). The other half is a magnet. They're often used to detect when a door or drawer is open, which is why they have mounting tabs and screws.