Omega Products 44018 User Manual

Linear Thermistor

E
Posi tive
Slope

out

E

in

R

1

R

2

T

2

T

1

E
Negative
Slope

out

E
Posi tive
Slope

out

E

in

R

1

R2R

3

T

3

T

2

E
Negative
Slope

out

T

1

R

1

R

2

RL

*

1

T

1

T

2

R

R

1

R2R

3

RL

*

1

T1T2T

3

R

Figure 1A
Thermistor
C

omposite 44018

Figure 1B
Thermistor
Composite 44019

Figure 1C
Thermistor
Composite 44020

Figure 2
Metal Film
Resistor

6.8 mm
(0.27")

Max.

2.0 mm
(0.08")

Max.

3.8 mm
(0.150)

Max.

150 mm

(6") Nom.

2.8 mm
(0.110")

Max.

3.8 mm
(0.150)

Max.

3.1 mm

(0.125")

Max.

7.1 mm
(0.28'')

Max.

2

.5 mm

(

0.100")
Max.

0.63 mm D
(0.025")

150 mm

(6") Nom.

150 mm

(6") Nom.

Components and Probes

OL-705-PP air probe, $73,
shown with Model 5830, $890,
sold separately, see Page M-96.

Linear Response Components

For applications requiring thermistors with linear
response to temperature change, OMEGA offers
linear components. These unique devices consist of
a thermistor composite for temperature sensing and
an external resistor composite for linearizing.

Thermistor composites 44018 and 44019 each contain
two thermistors packaged in a single sensor (Figures 1A
and 1B). Thermistor composite 44020 contains three
thermistors packaged in a single sensor (Figure 1C).

Resistor composites for use with 44018 and 44019
thermistor composites consist of two metal film resistors of
the size shown in Figure 2. Resistor composites for use
with the 44020 thermistor composite consist of three of
the same type metal film resistors.

Linear components are manufactured with different
values for different temperatures ranges. When they are
connected in networks shown in Figures 3 (A and B)
and 4 (A and B), they produce a varying voltage or
resistance which is linear with temperature.

One of the basic network manifestations is a voltage
divider as in Figure 3A for components other than #44212,
and as shown in Figure 3B for component #44212. The
area within the dashed lines represents the thermistor
composite. The network hookup for linear resistance
versus temperature is shown in Figure 4A for linear
components except #44212, and in Figure 4B for #44212.

Linear Voltage vs. Temperature Linear Resistance vs. Temperature

Following is a description of why these networks
produce linear information. The equation for a voltage
divider network, consisting of R and R0in series, is:

E

= E

out

in

R + R

where E
thermistor, and E

is the voltage drop across R. If R is a

out

is plotted versus temperature, the

out

total curve will be essentially non-linear and of a
general “S” shape, with linear or nearly linear portions
near the ends and in the center.

If R is modified by the addition of other thermistors and
resistors, linearity of the center section of the curve,
where sensitivity is greatest, can be extended to cover
a wide range of temperatures. This section follows the
general equation for a straight line, y = mx + b or in
terms of a linear component:

For Voltage Mode For Resistance Mode

E

= ±MT + b Rt= MT + b

out

where M is slope where M is slope

in volts/°T, in ohms /°T,

T is temperature T is temperature

in °C or °F, and in °C or °F, and

b is the value of b is the value of the

E

when T = 0° total network resistance,

out

Rt, in ohms when T = 0°

R

0

D

Figure 3A Figure 3B

Note: Model 5830 precision benchtop thermometer
includes linearized circuity, refer to section M.

Figure 4A Figure 4B

RL1may be any value as long as a new R1value

*

(R

) is selected to satisfy the relationship:

1A

D-42

R1A=

R1x RL

RL1– R

1

1

ensitivity is 400 times greater

S

han an IC thermocouple.

t

hermistor values as high as

T

0 mV/°C are common. In addition,

3

utput voltage can be applied to

o

recorder or digital voltmeter to

a

roduce a precise, sensitive,

p

irect reading thermometer.

d

Multiplexing

The 44018 thermistor composite
is used in four of the linear
components. The part that changes
in each component is the resistor
composite, which determines the
temperature range. Therefore, the
44018 thermistor composite can be
used over the entire -30 to 100°C
temperature range by simply
changing resistor composites.
Its accuracy and interchangeability
over the full range is ±0.15°C.
It is not mandatory that OMEGA

®

resistor composites be used with
the 44018 thermistor composite.
Any 0.1% resistors of the proper
values and with a temperature

coefficient of 30 PPM or less may
be substituted. In other situations,
it is frequently desirable to have
thermistor composite temperature
sensors at more than one location.

hermistor composite. It is possible

t

o multiplex any number of

t

hermistor composites through

t

single resistor composite for

a

reater design flexibility

g
When this is required, it is not
necessary to have a separate
resistor composite for each

MOST POPULAR MODELS HIGHLIGHTED!

To Order (Specify Model Number)

Linear Kit
Model No. Price Model No. Price Model No. Price

4201 $37 44018 $28 44301 $12

4
44202 37 44018 28 44302 12
44203 37 44018 28 44303 12
44204 37 44018 28 44304 12
44211A 57 44019 42 44311A 12
44212 90 44020 64 44312 19

See the next page for more information.
Ordering Examples: 44203, linear kit, 44018, dual thermistor composite plus 44303, resistor

composite sensor, $37 + 28 + 12 = $77.
44202, linear kit, 44018, dual thermistor composite plus 44302, resistor composite sensor, $37

+ 28 + 12 = $77.

†

Thermistor Resistor
Composite Composite

Component Specifications

†

Linear Components
Kit Model No. 44201 44202
Range 0 to 100°C 32 to 212°F -5 to 45°C 23 to 113°F
Thermistor Composite
Model No. 44018 44018
Resistor Composite
Model No. 44301 44302
Resistor R1= 3200 Ω,R
Composite Values R2= 6250 Ω R2= 12000 Ω

Thermistor Accuracy ±0.15°C ±0.27°F ±0.15°C ±0.27°F
& Interchangeability -30 to 100°C -22 to 212°F -30 to 100°C -22 to 212°F

E0Positive Slope E

(+0.0053483 Ein) T (+0.00297127 Ein) T (+0.0056846 Ein) T (+0.00315851 Ein) T

E0Negative Slope Eout = Eout = Eout = Eout =

(-0.0053483 Ein) T (-0.00297127 Ein) T (-0.0056846 Ein) T (-0.00315851 Ein) T

Resistance Mode Rt= Rt= Rt= Rt=

(-17.115) T +2768.23 (-9.508) T +3072.48 (-32.402) T +4593.39 (-18,001) T +5169.42

*Ein MAX 2.0 Volts 3.5 Volts
*ITMAX 625 µA 615 µA

***Load Resistance
Minimum R.L. 3 MΩ 10 MΩ

Linearity Deviation ±0.216°C ±0.388°F ±0.065°C ±0.12°F

* Ein Max and *ITMax values have been assigned to control thermistor self-heating errors so they do not enlarge the component error band;
i.e., the sum of the linearity deviation plus the probe tolerances. The values were assigned using a thermistor dissipation constant of 8MW/°C in
stirred oil. If better heat-sink methods are used or if an enlargement of the error band is acceptable, Ein Max. and ITMax values may be
exceeded without damage to the thermistor probe.

*** See Figure 1, example 1 on typical linear component application page D-45.
†† Kit includes thermistor composite and resistors.

°C °F °C °F

= 5700 Ω,

1

= E

out

+0.13493 Ein +0.03985 Ein +0.194142 Ein +0.093083 Ein

+0.86507 E

in

+0.96015 E

= E

out

in

= E

out

+0.805858 E

=

out

in

+0.906917 E

in

D-43