M, C, T
NTC Thermistors, Coated
POINT MATCH TOLERANCE
The standard leaded thermistors are calibrated and tested at 25°C to a tolerance of
±
5% or
±
10%; however, tighter tolerance,
point matched thermistors are readily available as are special point match temperatures to fit your application.
Since these thermistors have only one controlled point of reference ( the point match temperature ), the resistance at other
temperatures is given by the "Resistance VS Temperature Conversion Tables" for the appropriate material curve. The resistance
value at any temperature is the ratio factor times the resistance at 25°C.
Example: 1M1002-5, +70°C resistance = (Resistance factor for curve 1 at 70°C is .1990) X (10000 ohm resistance at 25°C)
= 1990 ohms.
The tolerance of the resistance at any temperature is described by Figure 2.
Vishay Dale
FIGURE 2
POINT MATCH TOLERANCES VS. TEMPERATURE
MAX. R VS. T
MIN. R VS. T
Point match resistance tolerances at temperatures other than
25ºC are not the same as the calibration temperature. This
difference is presented in Figure 2.
The tolerance at any given temperature is the point match
tolerance + the MT
±%
(Manufacturing Tolerance).
The MT
±%
may be obtained from the R vs. T Conversion
tables and is added to the point match temperature, i.e.,
±
1% Tol. at 25ºC +
±
2.6% at -30ºC for Curve 1 equals a total
tolerance of
±
3.6% at -30ºC.
RESISTANCE
NOMINAL R VS. T
PIVOT POINT
(CALIBRATION TEMPERATURE)
25
°
C
TEMPERATURE
COMPUTER AIDS FOR THERMISTOR SELECTION
A spreadsheet is available for the Vishay Thermistor Materials that calculates Beta, Steinhart-Hart Equation Constants A, B,
and C, the resistance at any temperature based upon the Steinhart constants or Beta, the temperature equivalent of the
resistance reading, and resistance temperature coefficients.
This spread sheet will also calculate the total resistance tolerance of any point matched thermistor for temperatures in 10ºC
increments, and the resistance tolerance at any temperature within the calibrated range of curve tracking thermistors. Please
contact factory if interested in this Excel™ spreadsheet.
Document Number: 33003
Revision 22-Sep-04
For technical questions, contact thermistor1@vishay.com
www.vishay.com
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