Rosemount 68-78 Data sheet

Sensors and Accessories (Volume 1)

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Series 68 Platinum RTD

January 2015

Rosemount Series 68 Platinum Resistance Temperature Sensors
measure from –50 to 400 °C (–58 to 752 °F). Series 68 Class B,
Pt100-385 sensors are available in capsule, general purpose, and
spring-loaded designs in sensor lengths from 1 to 48 inches.

Table 21 shows the interchangeability of the Series 68 RTD. As

an option, for maximum system accuracy, Emerson Process
Management can provide sensor calibration. See Sensor

characterization (calibration) schedules– Option Code V . In

addition, Emerson Process Management offers optional
sensor-to-transmitter matching capability obtainable through
the use of Callendar-Van Dusen Constants. See Option Code “V”

Callendar-van Dusen Constants .

Table 21. Series 68 Interchangeability

±0.55 °C (±0.99 °F) at -50 °C (-58 °F)

±0.30 °C (±0.54 °F) at 0 °C (32 °F)

±0.80 °C (±1.44 °F) at 100 °C (212 °F)

±1.30 °C (±2.34 °F) at 200 °C (392 °F)

±1.80 °C (±3.24 °F) at 300 °C (572 °F)

±2.30 °C (±4.14 °F) at 400 °C (752 °F)

Construction

Figure 7. Construction of a Platinum Thin Film RTD

Platinum element and lead wire
configurations

Single-element temperature sensors have four lead wires and
may be used in 2-, 3-, and 4-wire signal conditioning systems.

Specifications

Performance specifications

Temperature range

–50 to 400 °C (–58 to 752 °F)

Effect of temperature cycling

±0.05% (0.13 °C or 0.23 °F) maximum ice-point resistance shift
following 10 cycles over the specified temperature range

Stability

±0.11% 0.28 °C or 0.51 °F maximum ice-point resistance shift
following 1,000 hours at maximum specified temperature
(400 °C)

Maximum hysteresis

±0.1% of operating temperature range

Time constant

A. Connection Seal
B. Connection Pads
C. Connection Leads
D. Passivation with Glass Layers

Design and construction of the Series 68 Platinum Sensors
provides the optimum combination of accuracy and durability
available for temperature measurements. The construction of
the sensor allows for direct immersion in non-corrosive fluids at
reasonable static pressures. For corrosive environments or many
industrial applications, these sensors are widely used with
standard thermowell assemblies.

E. Photolithography Structured

Platinum Thin Film

F. Ce ra mic Su bs trat e

12 seconds maximum required to reach 63.2% sensor response
in water flowing at 3 ft/s (0.91 m/s)

Nominal R0 100 Ohm

Nominal alpha 0.00385 Ω/Ω°C

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January 2015

Sensors and Accessories (Volume 1)

Physical specifications

Material selection

Emerson provides a variety of Rosemount product with various
product options and configurations including materials of
construction that can be expected to perform well in a wide
range of applications. The Rosemount product information
presented is intended as a guide for the purchaser to make an
appropriate selection for the application. It is the purchaser’s
sole responsibility to make a careful analysis of all process
parameters (such as all chemical components, temperature,
pressure, flow rate, abrasives, contaminants, etc.), when
specifying product, materials, options and components for the
particular application. Emerson Process Management is not in a
position to evaluate or guarantee the compatibility of the
process fluid or other process parameters with the product,
options, configuration or materials of construction selected.

Sheath material

316 SST and 321 SST

Lead wire

PTFE insulated, silver plated, 24-gauge stranded copper wire

Environmental specifications

Humidity limits

Lead seal can withstand 100% relative humidity

Vibration limits

±0.05% maximum ice-point resistance shift due to 30 minutes of
14 g peak vibration from 5 to 350 Hz at 20 °C (68 °F) for
unsupported stem length of less than 6 inches

Quality assurance

Each sensor is subjected to a resistance accuracy test at
0 °C and an insulation resistance test

Enclosure ratings

When installed properly, Rosemount Series 68 sensors are
suitable for indoor and outdoor NEMA 4X and CSA Enclosure
Type 4X installations. See Hazardous area approvals for
complete installation information

Insulation resistance

1000 x 10
measured at 500 Vdc at room temperature

6

ohms minimum insulation resistance when

Identification data

The model, serial numbers, and up to six lines of permanent
tagging information are etched on each sensor adapter.
Stainless steel tags are available upon request.

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