ACCUCURVE™ Precision Thermistors
Ametherm manufactures precision resistancetemperature matched ACCUCURVE™ thermistors. These devices offer interchangeability over a broad temperature range and eliminate the need to individually calibrate or provide circuit compensation for part variability. Accurate temperature measurement to ±0.2°C is available over the 0°C to 70°C temperature range. Standard ohmic values at 25°C range from 2,252 to 100,000 ohms.
ACCUCURVE™ Selection Considerations
 Determine Resistance Value & Temperature Coefficient
 Review Power Dissipation
 Select Temperature Range
 Review Thermal Time Constant
Applications
There are numerous ways of measuring temperature electronically. Improvements in thermistor technology, coupled with the introduction of integrated circuitry, have made precision temperature measurement systems very cost effective
Microprocessors, A/D converters, interface electronics and displays are readily available. Circuit designs with builtin thermistor resistancetemperature algorithms have gained wide spread acceptance in precision temperature metrology.
Ametherms’s ACCUCURVE™ style thermistors are used in many applications that require a high degree of accuracy and reliability. They commonly perform temperature sensing, control, and compensation for medical, industrial, and automotive applications.
Interchangeable ACCUCURVE™ NTC thermistors are usually selected when a high degree of measurement accuracy is required over a wide temperature range. By modifying the Alpha equation the resistance and temperature tolerances can be calculated for various temperature intervals.
Because thermistors are nonlinear with respect to their resistancetemperature characteristics, Alpha therefore is nonlinear across their resistancetemperature range. As an example, a thermistor material curve with an Alpha of 4.4%/°C @ 25°C will have an Alpha of 3.8%/°C @ 50°C. For practical applications we recommend that the standardized R/T curves be used.
Ametherm ACCUCURVE™ thermistors can dissipate 1mW/°C. As a result, the possibility of error induced by excessive current flow, which would defeat the level of accuracy these devices are capable of representing, may exist in some circuits. To prevent this type of error, Ametherm recommends that circuit design engineers select the highest R value their circuit will tolerate for applications > 5 Volts to minimize any selfheating of the thermistor device. Refer to the ACCUCURVE™ Specifications table for resistance values and temperature tolerances.
Ametherm offers two standard R/T curves, “C” & “W”, with temperature coefficients of resistance of 4.4%/°C and 4.7%/°C, and Beta (ß) values of 3965°K and 4250°K. To determine the nominal resistance value of a thermistor at a specified temperature, multiply its resistance at 25°C value by the corresponding RT/R25 value for the desired temperature and applicable RT curve from the ACCUCURVE™.
Selection Considerations for NTC ACCUCURVE™ Devices Interchangeable ACCUCURVE™ NTC thermistors are usually selected when a high degree of measurement accuracy is required over a wide temperature range. By modifying the Alpha equation the resistance and temperature tolerances can be calculated for various temperature intervals.
ACCUCURVE™Specifications
Resistance @ 25° C (ohms)  Temperature Tolerance from 0° C to 70° C  Color Code  
±0.2° C  ±0.5° C  ±1.0° C  
Part Number  Part Number  Part Number  
2,252  ACC001  ACC011  ACC021  Brown 
3,000  ACC002  ACC012  ACC022  Red 
5,000  ACC003  ACC013  ACC023  Orange 
10,000  ACC004  ACC014  ACC024  Yellow 
30,000  ACW005  ACW015  ACW025  Green 
50,000  ACW006  ACW016  ACW026  Blue 
100,000  ACW007  ACW017  ACW027  Violet 
ACCUCURVE™Resistance/Temperature Table
TEMP (°C)  “C” CURVES  “W” CURVES  
2,252 ohm s @ 25°C  3,000 ohms @ 25°C  5,000 ohm s @ 25°C  10,000 ohm s @ 25°C  30,000 ohm s @ 25°C  50,000 ohm s @ 25°C  100,000 ohms @ 25°C  
40  75,780  100,950  168,250  336,500  1,204,600  2,007,700  4,015,500 
30  39,860  53,100  88,500  177,000  619,200  1,032,000  2,064,000 
20  21,860  29,121  48,535  97,070  331,030  551,720  110,3400 
10  12,460  16,599  27,665  55,330  183,560  305,940  611,870 
0  7,352.8  9,795.0  16,325  32,650  105,310  175,510  351,020 
10  4,481.5  5,970.0  9,950.0  19,900  62,354  103,920  207,850 
20  2,812.8  3,747.0  6,245.0  12,490  38,022  63,370  126,740 
25  2,252.0  3,000.0  5,000.0  10,000  30,000  50,000  100,000 
30  1,814.4  2,417.1  4,028.5  8,057.0  23,827  39,711  79,422 
40  1,199.6  1,598.1  2,663.3  5,327.0  15,314  25,524  51,048 
50  811.40  1,080.9  1,801.5  3,603.0  10,077  16,795  33,591 
60  560.30  746.40  1,244.0  2,488.0  6,777.1  11,295  22,590 
70  394.55  525.60  876.00  1,752.0  4,650.5  7,750.9  15,502 
80  282.63  376.50  627.50  1,255.0  3,251.2  5,418.7  10,837 
90  206.13  274.59  457.65  915.30  2,312.3  3,853.9  7,707.7 
100  152.75  203.49  339.15  678.30  1,670.8  2,784.6  5,569.3 
110  114.92  153.09  255.15  510.30  1,224.9  2,041.5  4,082.9 
120  87.671  116.79  194.65  389.30  909.99  1,516.7  3,033.3 
130  67.770  90.279  150.47  300.93  684.31  1,140.5  2,281.0 
140  52.983  70.581  117.64  235.27  520.30  867.16  1,734.3 
150  41.881  55.791  92.985  185.97  399.56  665.94  1,331.9 
The ACCUCURVE™ device can also be supplied with 32 AWG solid Teflon insulated leads of 3, 6, 9 and 12 inches in length. contact Ametherm applications engineering for additional information. Warning: Use Heat sinks when soldering to Thermistor Leads. 
ACCX0XX “C” CURVE  ACWX0XX “W” CURVE 




To determine the nominal resisteance value of a thermistor at a specified temperature, multiply its R_{T}/R_{25}value for the desired temperature and RT curve from the table above by its nominal resistance at 25 °C. 
More Information:
ACCUCurve Thermistors for Temperature Measurement and Control