Thermal resistor is normally by very sensitive to temperature, hot laziness the oxide of very small manganese, cobaltic, nickel is firing a kind when material of semiconductor pottery and porcelain makes nonlinear resistor, its block value can change as the change of temperature. Thermal resistor is negative temperature coefficient by temperature coefficient cent (NTC) , temperature coefficient (PTC) and critical temperature coefficient 3 kinds. The block value of temperature coefficient resistor lifts along with temperature and increasing, the block value of resistor of negative temperature coefficient lifts along with temperature and reduce, the block value of resistor of critical temperature coefficient is near critical temperature time base is originally 0.

 

Thermistor is straight hot formula mostly, namely when carrying electricity by resistor itself, give out heat and heat source is gotten. Still have in addition by hot type, want adscititious heat source. Common thermistor has form of circle, gasket, canal form to wait, its appearance sees graph 1 (a) .

 

 

Application is the at present widest is thermistor of negative temperature coefficient (NTC) , it can be divided again to measure lukewarm model, firm profiling, common model. Its are a lot of more phyletic and appearance each different, form of common written complaint having a canal, wafer. Homebred MTC product has MF51~MF57 (to be used at temperature to detect) , MF11~MF17 (is used at temperature compensation, temperature to control) , MF21~ MF22 (is used at circuit stabilized voltage) , MF31 (is measured with Yu Weibo power) wait for series.

 

temperature coefficient quick resistor (the applied range of PTC) is wider and wider, divide outside be being used at temperature control and temperature to measure circuit, midge of drive of the degauss circuit that still uses at colour television machine in great quantities and freezer, report implement, in the circuit of electric home appliances<gj such as electric iron. Homebred PTC product has MZ41~MZ42(to be used at midge of blower, drive implement, curl implement etc) , MZ01~MZ04 (starts circuit with the compressor at freezer) , the degauss circuit that MZ71~MZ75 (uses at colour television machine) , MZ61~MZ63 (is used at electromotor overheat to protect) , MZ2A~MZ2D (is used at current limliting.

 

 

Thermal resistor is nominal block value is to be below the condition that temperature is 25 C, measure with special apparatus. Below spare condition, resistor of usable also avometer is blocked undertake detecting, but when avometer detects because work electric current is bigger and form fuel factor, the value that often makes be measured and nominal block is worth not conform to. If ask only thick the block value that measures thermal resistor, with judging its the type is mixed whether regular job, usable avometer undertakes detecting by the following method:

 

(1) normal temperature detects. Stop avometer buy phone, two watches pen contacts thermal resistor two cite a base, avometer reading is the block value below normal temperature of the thermal resistor that be measured, see graph 6 (b) . Below the premise that chooses resistor correctly to block, if reading is 0 or infinity, explain thermal resistor already damaged.

 

(2) Zuo is lukewarm detect. Stand by electric iron thermal resistor as heat source, 6 (b seeing a picture) , the block that is like avometer to show is worth relatively value of normal temperature block has apparent change to removed electric iron criterion block value restores to be worth to normal temperature block, making clear thermal resistor is good.

 

(3) low temperature detects. With avometer clip clips thermal resistor two cite a base, put thermal resistor freezer inside. Normal when, lose the thermal resistor of temperature coefficient, the block value that avometer indicates compares value of normal temperature block to increase apparently; the heat of temperature coefficient quick block value, the block value that avometer indicates compares value of normal temperature block to drop apparently.

 

 

(1) is become when temperature of environment of temperature prep above, hold thermal resistor with the hand, should observe the change of resistor reading.

 

(2) detects every time PTC thermal resistor should arrive in its thermal drop after room temperature undertake.