TEMPERATURE SENSORS AND LST NETWORKS - Vishay Telefunken

micro-measurements@vishay.com

Temperature Sensors and LST Networks

Vishay Micro-Measurements

Document Number: 11522

Revision 03-Sep-03

www.vishaymg.com

100

Special Purpose Sensors - Temperature

Resistance thermometry is a widely employed method of

measuring temperature, and is based on using a material

whose resistivity changes as a function of temperature.

Resistance Temperature Detectors (RTD’s) have fast

response time, provide absolute temperature measurement

(since no reference junctions are involved), and are very

accurate. Their measurement circuits are relatively simple,

and the sensors, when properly installed, are very stable

over years of use.

Vishay Micro-Measurements resistance temperature

sensors are constructed much like wide-temperature-range

strain gages. The standard sensors utilize nickel or nickel/

manganin grids, although special-purpose gages are also

available in Balco

alloy or copper foil grids. These

temperature sensors are bonded to structures using

standard strain gage installation techniques, and can

measure surface temperatures from –452° to approximately

+500°F (–269° to +260°C). Because of their extremely low

thermal mass and the large bonded area, the sensors follow

temperature changes in the structural mounting surface with

negligible time lag.

Balco is a trademark of the W.B. Driver Company

TG TEMPERATURE SENSORS

TG Temperature Sensors are normally selected for

measurements from –320° to +500°F (–195° to +260°C).

The sensing grid utilizes a high purity nickel. Three basic

constructions are offered:

ETG Sensors have a polyimide carrier for flexibility. It is

available as an encapsulated gage with exposed solder tabs

(Option E), or with integral printed-circuit terminals (Option W).

The WTG Sensor incorporates integral leadwires and a

high-temperature epoxy-phenolic matrix (reinforced with

glass fiber) which fully encapsulates the grid.

The WWT-TG Sensor is a slightly larger version of the WTG,

but preattached to a 0.005-in (0.13-mm) thick stainless steel

shim. This gage can be welded or bonded to a structure.

The resistance at +75°F (+23.9°C) is 50Ω ±0.3% for the ETG

and WTG Sensors; and 50Ω ±0.4% for the WWT-TG

Sensors.

Maximum operating temperature for ETG Sensors with

Option E is +450°F (+230°C), and +350°F (+175°C) for

Option W. All other types are +500°F (+260°C).

TEMPERATURE SENSOR SELECTION

In addition to the standard line of temperature sensors described above, Vishay Micro-Measurements can furnish almost any

type of sensor pattern desired, in a wide range of resistances. Contact our Applications Engineering Department for details.

DIMENSIONS

GAGE PATTERN

AND DESIGNATION GAGE OVERALL GRID OVERALL

Approximate Size Shown LENGTH LENGTH WIDTH WIDTH Length Width

0.060 0.148 0.100 0.100 0.28 0.20

1.52 3.76 2.54 2.54 7.0 4.8

0.125 0.235 0.125 0.125 0.33 0.19

3.18 5.97 3.18 3.18 8.3 4.7

0.060 0.148 0.100 0.100 0.28 0.20

1.52 3.76 2.54 2.54 7.0 4.8

0.125 0.235 0.125 0.125 0.33 0.19

3.18 5.97 3.18 3.18 8.3 4.7

0.20 0.71 0.200 0.43 0.52 0.26

5.08 18.03 5.08 10.92 13.1 6.6

MATRIX

WWT-TG-W200B-050

For weldable temperature sensor,

see appropriate datasheet

50A/E 50B/E Opt W

Feature

50A 50B

WTG-50A

WTG-50A/Option W

WTG-50B

WTG-50B/Option W

ETG-50A/Option E

ETG-50A/Option W

ETG-50B/Option E

ETG-50B/Option W

Opt W

Feature

(shim length) (shim width)

inches

millimeters

micro-measurements@vishay.com

Temperature Sensors and LST Networks

Vishay Micro-Measurements

Document Number: 11522

Revision 03-Sep-03

www.vishaymg.com

101

Special Purpose Sensors - Temperature

TG LST MATCHING NETWORKS

The temperature coefficient of resistance of nickel sensors is

very high but nonlinear as indicated in the graph. The sensor

resistance can be measured directly and converted to

temperature with the charts supplied in Tech Note TN-506,

but since TG Sensors are commonly used along with strain

gages, special matching networks have been developed to

use with strain gage instrumentation.

These LST Matching Networks are small passive devices

encapsulated in a molded epoxy case. They are connected

between TG Temperature Sensors and the strain gage

readout instrumentation to perform the following three

functions:

1. Linearize the gage resistance versus temperature.

2. Attenuate the resistance change slope to the equivalent

of 10 or 100 microstrain per degree F or C for a gage

factor setting of 2.000 on the strain indicator.

3. Present a balanced 350-ohm half-bridge circuit to the

strain indicator at the reference temperature of 0°F

(Fahrenheit networks) or 0°C (Celsius networks).

In order to optimize performance, separate network designs

are available for cryogenic and normal temperature ranges.

Environmental temperature range of LST networks is –65° to

+250°F (–55° to +125°C). Standard strain gage instrumenta-

tion, such as the Vishay Micro-Measurements Model P-

3500, is ideal for use with these sensors, eliminating the

need to purchase separate readout devices.

SENSOR

NETWORK OUTPUT TEMPERATURE

DESIGNATION SLOPE RANGE

LST-10F-350C 10 microstrain/°F –320° to +100°F

LST-10C-350C 10 microstrain/°C –200° to +25°C

LST-100F-350C 100 microstrain/°F –320° to +100°F

LST-100C-350C 100 microstrain/°C –200° to +25°C

LOW TEMPERATURE RANGE

SENSOR

NETWORK OUTPUT TEMPERATURE

DESIGNATION SLOPE RANGE

LST-10F-350D 10 microstrain/°F –200° to +500°F

LST-10C-350D 10 microstrain/°C–150° to +260°C

LST-100F-350D 100 microstrain/°F –200° to +500°F

LST-100C-350D 100 microstrain/°C–150° to +260°C

NORMAL TEMPERATURE RANGE

Sensor

50Ω

@ +75°F

(+23.9

LST NETWORK

Active

Dummy

Strain Indicator

-100 0 +100 +200

Temperature in

-200 -100 0 +100 +200 +300 +400 +500

Temperature in

100

110

120

130

140

Typical data for 50

Ω

nickel sensor.

micro-measurements@vishay.com

Temperature Sensors and LST Networks

Vishay Micro-Measurements

Document Number: 11522

Revision 03-Sep-03

www.vishaymg.com

102

Special Purpose Sensors - Temperature

CLTS-2B TEMPERATURE SENSORS

The Cryogenic Linear Temperature Sensor (CLTS) is recom-

mended for best accuracy over the temperature range of –

452° to +100°F (–269° to +40°C). The CLTS-2B is a small

surface thermometer gage consisting of two thin foil sensing

grids laminated into a glass-fiber-reinforced epoxy-phenolic

matrix, and electrically wired in series. The two alloys are

special grades of nickel and manganin that are processed for

equal and opposite nonlinearities in resistance versus tem-

perature characteristics. The CLTS-2B is fabricated with in-

tegral printed-circuit terminals to provide strong, convenient

attachment points for the leadwires. Gage construction is

illustrated at right.

Because of its low thermal mass and thin construction, the

CLTS-2B responds quickly and accurately to temperature

changes in the surface to which it is bonded. Special design

features protect the sensor from damage due to thermal

shock, even during plunges from room temperature directly

into liquefied gases, including LHe at –452°F (–269°C).

Avoid prolonged exposure of the CLTS-2B to tempera-

tures above +150°F (+65°C) as this may adversely affect

characteristics of the manganin material. The maximum

recommended curing temperature of the bonding adhe-

sive is two hours at +200°F (+95°C).

CLTS-2B SENSITIVITY

The nominal resistance of the CLTS-2B is 290.0 ohms ±0.5%

at +75°F (+23.9°C). The resistance decreases linearly with

temperature, reaching a nominal value of 220.0 ohms at

–452°F (–269°C). This represents a change of 70 ohms for

527°F, or a slope of 0.1328 ohms per degree F; the

corresponding slope on the Celsius scale is 0.2391 ohms per

degree C. With proper instrumentation a resolution of 0.01°

can be easily achieved. Data readout can be accomplished

by directly monitoring resistance change with an appropriate

resistance measuring instrument.

CLTS MATCHING NETWORKS

When used in conjunction with bonded strain

gages, it is often most convenient to modify

the CLTS output with a simple, passive

resistance network that can be used with

strain gage instrumentation as described with

the TG Sensors. The sensitivity can be

DIMENSIONS

GAGE PATTERN

AND DESIGNATION GAGE OVERALL GRID OVERALL

Actual size shown. LENGTH LENGTH WIDTH WIDTH Length Width

CLTS-2B 0.130 0.205 0.280 0.280 0.43 0.31

3.30 5.21 7.11 7.11 10.9 7.9

MATRIX

adjusted to 10 microstrain per degree F (CLTS-N-F) or C

(CLTS-N-C); with a resolution of 0.1° when used with most

strain indicators. This type of network also provides a high

degree of leadwire compensation. Environmental tempera-

ture limits for CLTS Networks are –65° to +250°F (–55° to +125°C).