NTC Thermistors - Disc and Chip Style

Temperature Measurement and Control Thermistors

DISC and CHIP Style

ROHS

DISC & CHIP NTC 
STYLE NTC THERMISTOR
Features


 

 
  • Wide Ohmic Value Range
  • Accurate & Stable
  • Fast Thermal
    Response Time
  • Tight Tolerances
  • High Sensitivity

NTC Thermistors

Negative Temperature Coefficient (NTC) thermistors are thermally sensitive semiconductor resistors which exhibit a decrease in resistance as absolute temperature increases. Change in the resistance of NTC thermistor can be brought about either by a change in the ambient temperature or internally by self-heating resulting from current flowing through the device. Most of the practical applications of NTC thermistors are based on these material characteristics.
 

NTC DISC & CHIP Style Devices

RTI manufacturesDISC & CHIPstyle thermistors in resistance values ranging from 1.0 ohm to 500,000 ohms. These devices are suitable for a range of resistance values and temperature coefficients from relatively low resistance and temperature coefficients to very high values. Precision resistance tolerances are available to 1%. Standard resistance tolerances are from 5% to 20%. All tolerances are specified at 25°C or may be specified at any temperature within the operating temperature range of the thermistor.
 

Thermistor Terminology for Temperature Measurement & Control Devices

  • D.C. – The dissipation constant is the ratio, normally expressed in milliwatts per degree C (mw/°C), at a specified ambient temperature, of a change in power dissipated in a thermistor to the resultant change in body temperature.
  • T.C.- The thermal time constant is the time required for a thermistor to change 63.2% of the total difference between its initial and final body temperature when subjected to a step function change in temperature under zero-power conditions and is normally expressed in seconds (S).
  • Alpha () or Temperature Coefficient or Resistance- The temperature coefficient of resistance is the ratio at a specified temperature, T, of the rate of change of zero-power resistance with temperature to the zero-power resistance of the thermistor. The temperature coefficient is commonly expressed in percent per degree C (%/°C).

NTC DISC & CHIP
Selection
Considerations


  • Select Req’d. Resistance Value & Temperature Coefficient
  • Determine Accuracy Req’d.
  • Review Power Dissipation
  • Determine Operating Temperature Range
  • Review Thermal Time Constant

Thermistor Applications

Time and temperature are two of the most frequently measured variables. There are numerous ways of the measuring temperature electronically, most commonly by thermocouples and negative temperature coefficient (NTC) thermistors. For general purpose temperature measurement, NTC temperature sensors can operate over a wide temperature range (-55 to +300°C). They are stable throughout a long lifetime, and are small and comparatively inexpensive. Typically, they have negative temperature coefficients between -3.3 and -4.9%/°C at 25°C. This is more than ten (10) times the sensitivity of a platinum resistance thermometer of the same nominal resistance. RTI’sDISC & CHIPstyle thermistors are used in many applications that require a high degree of accuracy and reliability.
Some of the most popular applications of NTC thermistors include:
  • Temperature Compensation
  • Temperature Measurement & Control
  • Fan Motor Control
  • Fluid Level & Temperature Sensors

 NTC DISC & CHIP – Selection Process

  • Select R Value
  • Determine R @ T
  • Calculate DEV for R @ T
  • Evaluate Power Rating (D.C.)
  • Review T.C. Requirements

Selection considerations for NTC DISC & CHIP Devices

Power dissipation is a common problem in the use of thermistors as they can only dissipate a certain amount of power.
  • If the power dissipated exceeds the dissipation constant (D.C.) rating of the sensor it is likely that it will exhibit self heating.
  • Most thermistors dissipate from 1 to 25 mW/°C nominal. This means that the resistance changes by an equivalent of 1°C for each D.C. rating (mW/°C) for the selected device.
  • To maintain a higher degree of accuracy, temperature error caused by self-heating should be an order of magnitude less than the required sensor accuracy. For many applications, this degree of accuracy is not required and a less stringent de-rating may be adequate.
  • Several options to reduce the thermistor power are to increase the thermistor resistance, lower the source voltage and/or increase the series resistor in the divider circuit.
 
As an example,
  • if the D.C. of the thermistor selected is 5 mW/°C and the power dissipated by the device is 20 mW/°C, then a 4°C error is induced due to the effect of self-heating.
  • To minimize this effect, a factor can be derived simply by taking the DC rating times 10-1(one order of magnitude lower) and use it in the power equation to produce a good approximation of the maximum allowable power.
  • For instance, if the desired accuracy is 1°C, and the rated D.C. of the device selected is 5 mW/°C, adjusting the specified D.C. rating in the power equation to 0.5 mW/°C compensates for self-heating error and effectively predicts the maximum power the device can dissipate without significantly affecting the desired accuracy.
  • The resulting maximum power that should be applied would be calculated as 1°C*0.5mW/°C = 0.5mW.
 

NTC Standard Disc Thermistor Specifications

Part
Number
Resistance
@25°C
(Ohms) ±10%
R-T
Curve
D
(in.)
THK
 (in.) 
D.C.T.C.Leads
AWG#
S
 (in)
Get-It-Now
Mouser
1DA101J100A0.10.06310280.07995-1DA101J
1DA101J-EC100A0.10.06310280.07995-1DA101J-EC
1DA101K100A0.10.06310280.07995-1DA101K
1DA101K-EC100A0.10.06310280.07995-1DA101K-EC
1DA131J130A0.10.06310280.07995-1DA131J
1DA131K130A0.10.06310280.07995-1DA131K
1DA500J50A0.10.0336280.07995-1DA500J
1DA500K50A0.10.0336280.07995-1DA500K
1DB102J1,000B0.10.06310280.07995-1DB102J
1DB102K1,000B0.10.06310280.07995-1DB102K
1DB102K-EC1,000B0.10.06310280.07995-1DB102K-EC
1DB501K500B0.10.0336280.07995-1DB501K
1DC103J10,000C0.10.0336280.07995-1DC103J
1DC103J-EC10,000C0.10.08412280.07995-1DC103J-EC
1DC302J3,000C0.10.08412280.07995-1DC302J
1DC502J5,000C0.10.08412280.07995-1DC502J
1DC502J-EC5,000C0.10.08412280.07995-1DC502J-EC
1DE104J100,000E0.10.9539280.07995-1DE104J
1DE104K100,000E0.10.9539280.07995-1DE104K
1DE104K-EC10,000E0.10.9539280.07995-1DE104K-EC
2DA200J20A0.20.05720240.1995-2DA200J
2DA200K20A0.20.05720240.1995-2DA200K
2DA503J50000A0.20.05720240.1995-2DA503J
2DB101K100B0.20.025718240.1995-2DB101K
2DB102J1000B0.20.025718240.1995-2DB102J
2DB102J-EC1000B0.20.025718240.1995-2DB102J-EC
2DB102K1000B0.20.025718240.1995-2DB102K
2DB151J150B0.20.025718240.1995-2DB151J
2DB151K150B0.20.035719240.1995-2DB151K
2DC102K1,000C0.20.035718240.1995-2DC102K
2DC302J3000C0.20.1730240.1995-2DC302J
2DC302K3,000C0.20.1730240.1995-2DC302K
2DE103J10000E0.20.04717240.1995-2D103J
2DE103K10000E0.20.04717240.1995-2DE103K
2DE503K50000E0.20.04717240.1995-2DE503K
3DA100J10A0.30.06848240.1995-3DA100J
3DA100K10A0.30.06848240.1995-3DA100K
3DB500J50B0.30.025835240.1995-3DB500J
3DB500K50B0.30.025835240.1995-3DA500K
3DE502J5000E0.30.025835240.1995-3DE502J
3DE502K5000E0.30.025835240.1995-3DE502K