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INTRODUCTION
A thermistor, or thermally sensitive resistor, is a resistor that changes resistance with a change in temperature.
There are two basic types of thermistors, PTC and NTC. A PTC (Positive Temperature Coefficient) device will
increase resistance with an increase in temperature; an NTC (Negative Temperature Coefficient) device
will decrease resistance with an increase in temperature. QTI manufacturers both PTC and NTC devices in a
broad selection of styles and resistance values.
Quality Thermistor, Inc. has delivered high quality thermistors and assemblies to a worldwide market since 1977.
Our modern ISO9001 certified manufacturing facility located in the USA, combined with our assembly plant in
Mexico, are equipped with state of the art manufacturing equipment to completely design and
manufacture a full spectrum of devices.
We at QTI pride ourselves on our friendly and knowledgeable staff. Please feel free to call, fax, or e-mail us
directly with any questions you may have about thermistors and thermistor applications. Our application
engineers are available to offer ideas and technical support for any of your design projects.
TABLE OF CONTENTS
I. PTC THERMISTORS
1.
2.
3.
4.
5.
PTC THERMISTOR CHARACTERISTICS
PTC THERMISTORS (DISCRETE MILITARY AND COMMERCIAL GRADE)
PTC THERMISTORS (HYBRID CHIP)
PTC SMD (EPOXY MOUNT)
PTC T0220 OVERTEMPERATURE PROTECTORS
II. NTC THERMISTORS
6. NTC THERMISTORS (NON-INSULATED LEADS)
7. NTC THERMISTORS (INSULATED LEADS)
8. NTC PRECISION INTERCHANGEABLE THERMISTORS (NON-INSULATED LEADS)
9. NTC PRECISION INTERCHANGEABLE THERMISTORS (INSULATED LEADS)
10. NTC MILITARY THERMISTORS (RTH44)
11. NTC MILITARY THERMISTORS (RTH06)
12. NTC SMD 0805 THERMISTORS
13. NTC MONOLITHIC GLASS PACKAGED THERMISTORS
14. NTC T0220 THERMISTORS
15. NTC PROBE ASSEMBLIES (LIQUID TYPE)
16. NTC PROBE ASSEMBLIES (SURFACE TYPE)
17. NTC RESISTANCE VS. TEMPERATURE TABLES
18. NTC RESISTANCE VS. TEMPERATURE TABLES
19. NTC RESISTANCE VS. TEMPERATURE TABLES
APPENDIX A: APPLICATION NOTES: "Basic Temperature Measurement Using Thermistors"
APPENDIX B: APPLICATION NOTES: "Temperature Compensation Using Thermistors"
APPENDIX C: APPLICATION NOTES: "Computer Interfacing to an NTC Thermistor"
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POSITIVE TEMPERATURE COEFFICIENT THERMISTORS
Positive Temperature Coefficient (PTC) thermistors have a resistance gain of approximately .7% per degree centigrade and exhibit a linear
resistance vs. temperature change over given increments of temperature change.
They are suitable for applications in temperature measurements, temperature control, amplifier stabilization, power control, microprocessor
interfacing, and numerous other applications where temperature control/compensation is required.
OPERATING PARAMETERS
TEMPERATURE VS. "COEFFICIENT OF RESISTANCE" TABLES
The following tables will give the resistance value of the thermistor at any temperature (Rt).
To determine the resistance value of the thermistor at any temperature (Rt):
Find the temperature in the vertical column “temperature”. Find the resistance range of the thermistor at 25°C (R25°C) in the
appropriate horizontal column. The intersection of the two columns will give the coefficient of resistance (Rc) of the thermistor
at the desired temperature. Compute as follows:
R25°C + (Tolerance x Rc) = Rt + Maximum Deviation
R25°C = thermistor resistance at 25°C
Rc = coefficient of resistance at desired temperature
Rt = resistance of thermistor at desired temperature T
Maximum Deviation = tolerance in percent taken from Table III at a temperature other than 25°C
POWER DERATING
Power dissipation in the thermistor causes a resultant rise in the case temperature of the thermistor. The maximum allowable temperature of
the thermistor is 125°C. The thermistor must be power derated according to the Derating Curve, PTC Figure 1.
PTC TABLE I - STANDARD FOR RTH42 (MIL-R-23648/19) AND QTG SERIES, QTCII
TEMPERATURE
10 TO 68
OHMS
82 TO 150
OHMS
180 TO 470
OHMS
560 TO 1200
OHMS
1500 TO 5600
OHMS
6800 TO 10,000
OHMS
*(-55°C)
-15°C
0°C
25°C
50°C
75°C
*(100°C)
*(125°C)
0.615
0.790
0.863
1.000
1.160
1.350
1.545
1.750
0.582
0.770
0.847
1.000
1.170
1.370
1.584
1.800
0.560
0.755
0.838
1.000
1.180
1.400
1.623
1.860
0.550
0.740
0.835
1.000
1.200
1.420
1.656
1.920
0.515
0.730
0.825
1.000
1.230
1.450
1.670
1.960
0.510
0.730
0.825
1.000
1.190
1.400
1.610
1.830
PTC TABLE II - STANDARD FOR RTH22 (MIL-R-23648/9) AND QTM SERIES
TEMPERATURE
10 TO 68
OHMS
82 TO 150
OHMS
180 TO 560
OHMS
680 TO 1500
OHMS
1800 TO 5600
OHMS
6800 TO 10,000
OHMS
PTC TABLE III - DEVICE TOLERANCE AT
TEMPERATURES OTHER THAN 25°C
SEQUENCE TEMPERATURE
F
+/- %
G
+/- %
J
+/- %
K
+/- %
*(-55°C)
-15°C
0°C
25°C
50°C
75°C
*(100°C)
*(125°C)
0.615
0.790
0.863
1.000
1.160
1.350
1.545
1.750
0.582
0.770
0.847
1.000
1.170
1.370
1.584
1.800
0.560
0.755
0.838
1.000
1.180
1.400
1.623
1.860
0.550
0.740
0.835
1.000
1.200
1.420
1.656
1.920
0.515
0.730
0.825
1.000
1.230
1.450
1.670
1.960
0.481
0.712
0.814
1.000
1.210
1.430
1.670
1.900
1
2
3
4
5
6
7
8
-55°C
-15°C
0°C
25°C
50°C
75°C
100°C
125°C
15
9
3
1
3
5
7
10
17
10
4
2
4
6
9
12
20
13
7
5
7
9
12
15
25
18
12
10
12
14
17
20
*Multipliers applicable to military grades only
PTC FIGURE 1 -
DERATING CURVE
PERCENT OF MAXIMUM POWER
100
80
60
40
20
0
-55
125°C
-20
0
20
40
80
120
140
160
25°C
ORDERING INFORMATION
QTG12 202F
STYLE DESIGNATION
FIRST TWO RESISTANCE DIGITS
NUMBER OF ZEROS
TOLERANCE:
K
= 10%
J=
5%
G
= 2%
F
= 1%
10% IS STANDARD TOLERANCE
AMBIENT TEMPERATURE (°C)
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PTC COMMERCIAL GRADE STYLES
OPERATING
TEMPERATURE
RANGE
QTM12 - MOLDED TYPE
.155" DIA.
.025" NOM.
TIMMED COPPER
.421"
1.37"
STANDARD
RESISTANCE RANGE
POWER RATING AT
25°C IN WATTS
THERMAL TIME
CONSTANT
SECONDS MAXIMUM
-65°C TO +125°C
10 - 40K OHMS
.500*
*derate per Figure 1
30
QTG12 - GLASS TYPE
.105" DIA.
.300"
.020" NOM.
TIMMED DUMET
1.200"
-65°C TO +125°C
10 - 10K OHMS
.125*
*derate per Figure 1
55
QTG10 - GLASS TYPE
.070" DIA.
.170"
.015" DUMET LEADS
-55°C TO +125°C
10 - 3.3K OHMS
.062*
*derate per Figure 1
10
1.100"
PTC MILITARY GRADE STYLES
MEET OR EXCEED MIL-R-23648D
RTH22 - MIL-R-23648/9
.155" DIA.
.025" NOM.
TIMMED COPPER
.421"
1.37"
-55°C TO +125°C
10 - 10K OHMS
.500 @ 25°C*
*derate per Figure 1
60
RTH42 - MIL-R-23648/19
.105" DIA.
.300"
.020" NOM.
TIMMED DUMET
1.200"
-55°C TO +125°C
10 - 10K OHMS
.250 @ 25°C*
*derate per Figure 1
60
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POSITIVE TEMPERATURE COEFFICIENT
CHIP THERMISTOR
STANDARD CONFIGURATION
RESISTANCE
OHMS @ 25° C
PART
NO.
L
+/- .010
W
+/- .010
T
+/- .010
NOMINAL
D.C.*
T.C.*
10
W
QTC11 -100
-120
-150
-180
-220
-270
-330
-390
-470
-560
-680
-820
-101
-121
-151
-181
-221
-271
-331
-391
-471
-561
-681
-821
-102
-122
-152
-182
-222
-272
-332
-392
-472
-562
-682
-822
-103
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.038
.038
.038
.038
.038
.038
.038
.030
.022
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.032
.038
.038
.038
.038
.038
.038
.038
.030
.022
.028
.028
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.050
.072
.072
.072
.072
.072
.072
.072
.072
.072
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
2MW
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
8 sec.
12
15
18
L
22
27
33
39
GOLD
TERMINATIONS
T
47
56
68
82
100
ENGINEERING INFORMATION
DISSIPATION CONSTANT .............................. DEPENDENT
ON MOUNTING
THERMAL TIME CONSTANT ......................... DEPENDENT
ON MOUNTING
RESISTANCE COEFFICIENT. .................. SEE PTC TABLE I
120
150
180
220
270
330
390
470
MOUNTING ............................................... WIRE BOND OR
CONDUCTIVE EPOXY
560
680
820
1000
NOTE:
FOR R/T CURVE, SEE PTC TABLE I
1200
1500
1800
ORDERING INFORMATION
PART NUMBER IS FORMED AS FOLLOWS:
2200
2700
3300
3900
4700
5600
QTC11 - 100K
PART NUMBER
TOLERANCE CODE SUFFIX
K
= 10%
J
= 5%
G
= 2%
F
= 1%
6800
8200
10000
*D.C. = DISSIPATION CONSTANT MW/C
*T.C. = TIME CONSTANT SECONDS IN FREE AIR
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PTC MICROELECTRONIC
SURFACE MOUNT THERMISTOR
WRAP AROUND SILVER TERMINATIONS
SUITABLE FOR EPOXY BONDING
L
0.010
T
W
WRAP AROUND SILVER TERMINATIONS - SUITABLE FOR EPOXY BONDING
RESISTANCE @ 25°C
(Ohms)
PART NO.
W
+/-0.005
T
+/-0.005
L
+/-0.010
NOMINAL
*D.C.
NOMINAL
*T.C.
33
47
100
330
470
1000
3300
QTCH-330X
QTCH-470X
QTCH-101X
QTCH-331X
QTCH-471X
QTCH-102X
QTCH-332X
.030
.030
.030
.030
.030
.030
.030
.020
.022
.030
.020
.023
.016
.020
.050
.050
.050
.050
.050
.050
.050
2mW/C
2mW/C
2mW/C
2mW/C
2mW/C
2mW/C
2mW/C
8 sec
8 sec
8 sec
8 sec
8 sec
8 sec
8 sec
*MINIMUM DISSIPATION CONSTANT
*MAXIMUM THERMAL TIME CONSTANT AS MEASURED IN FREE AIR
ORDERING INFORMATION
PART NUMBER IS FORMED AS FOLLOWS:
ENGINEERING INFORMATION
Dissipation Constant
Thermal Time Constant
Dependent on Mounting
Dependent on Mounting
SEE PTC TABLE 1
Conductive Epoxy
0.0625 watts @ 25°C
-55°C to 125°C
QTCH-____X
TOLERANCE DESIRED
Resistance Coefficient
Mounting
Power Rating
TOLERANCE:
K=10%
J=5%
G=2%
F=1%
Operating Range
FOR ADDITIONAL ENGINEERING INFORMATION PLEASE CONTACT
FACTORY FOR TECHNICAL BULLETIN #QT05015-001
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