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UNITECH INSTRUMENTATION :::
MUMBAI - 400 086 |
RESISTANCE
TEMPERATURE
DETECTORS |
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Resistance temperature detectors (RTD) are
temperature sensors, which work on principles for
resistance offered by metallic element and its variation based on
temperature. Metals which provide
predictable, stable and linear resistance gradient are generally used for
this purpose.
Many metals exhibit these properties. Of which copper, Platinum, Silver
and Gold are commonly
used.
Copper is used for cryogenic and sub-zero applications. Commonly available
element is
Cu53 : 53 Ohm resistance at Zero Deg Temperature.
Where as Platinum is used for most industrial applications. Commonly
available elements are Pt50,
Pt100, Pt200, Pt500 and Pt 1000.
Pt100: 100 Ohm resistance @ 0 Deg C is by far the most popular and easily
available element.
RTD elements are classified in various categories based on its accuracy
such as:
Class - A, Class - B, Band1 to Band 5.
RTD ELEMENT CONSTRUCTION :
For laboratory applications Platinum wire embedded in Glass capsules
are available.
However for industrial purpose fragility and price restrict their use.
For industrial applications two most popular constructions are :
Wire wound ceramic bulbs and thin film type elements.
Wire wound elements are more stable and offer wider temperature range
where as film type are
economical and are restricted to low temperature applications.
RTD STANDARDS:
IEC - 751:1983, DIN 43760, BS EN 60751:1969 are commonly used calibration
and
tolerance standards for RTD elements.
Typical Class A element Error is 0.15 Deg C @ 0 Deg C and
Typical Class B element Error is 0.3 Deg C @ 0 Deg C.
Tolerance values of all stadard RTD elements are plotted on the following
page of this
catalogue.
Standard Pt100 RTD elements are constructed from Pt having Alpha
coefficient at 0.00385 /
Deg C and resistance of 100 ohms at 0 Deg C.
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RTD ASSEMBLIES: |
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Satiable for general application
up to 200 Deg C. Film
and Ceramic type element in Seamless SS316 sheath with
extension lead wire in two / three wire construction. |
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Hand held RTD assemblies are
suitable for liquid, Gas and semi
solid, Available in Pt 100 film and Ceramic element with Mior
rigid SS Sheath and Ebonite handle with PVC extension cable
Suitable for Temp up to 180 Deg C. |
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Bayonate type suitable for
plastic machinery, bearing chokes
etc. Available in Film and Ceramic type element with SS 316
sheath and extension lead wire. Suitable for Temp up to
250 Deg C. |
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Heavy duty metal sheathed industrial RTD assemblies are
suitable for most arduous industrial environments. Available in
Ceramic Element in Accuracies such as Class B,A, Band 1, 2 and
3 with variety of sheaths such as SS 304, SS 316 and SS 310. |
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Mineral insulated metal sheathed RTD Assemblies are suitable
for spaces which are difficult to reach. Available in Ceramic
element with variety of sheaths such as SS 304, SS 316 and SS
310. |
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TYPES OF RTD
HEADS |
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Features
Heavy duty industrial metal
sheathed RTD assemblies are
available with thick walled
protective sheath in SS 304,
SS 316, SS 310 and SS 446.
These assemblies generally
employ Ceramic elements are
suitable for temperatures upto
350 Deg C. However assemblies
with Film RTD element can be
offered if required. Depending
upon selection of sheath these
assemblies are suitable for
Oxidising, reducing or neutral
atmosphere.
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HAND HELD IMMERSION
PROBES:
These probes are available
with exposed element for gas
and air temp measurement,
enclosed elements for liquid
temp. Measurement.
Probe extensions are either
straight or angled to suit
difficult to reach areas.
Needle point tips can be
offered for food stuff temp
measurement.
Extension leads are either
PVC insulated, PTFE insulated
on fibreglass insulated
with SS wire braiding.
Terminal ends are either
miniature socket or BNC
coupler. Elements used are
generally mini ceramic
elements with 1 ot3 mm
Dia x 5 to 15 mm
length with Class B accuracy.
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Features
Mineral insulated assemblies are
used where fast response, high
integrity and mechanical
flexibility is desired. Available in
simplex and duplex leads from
1.6 to upto 8 mm OD. The lead
wires are insulated from each
other and sheath by tightly
compacted MgO powder offering
insulation resistance upward of
50 m-Ohms. Flexible metal
sheathed RTD assemblies
are available with protective
sheath in SS 304, SS 316,
SS 310 Inconel 600. These
assemblies are suitable for
temperatures up to 350 Deg
C when suitable element is used.
Depending upon selection of
sheath these assemblies are
suitable for Oxidising, reducing
or neutral atmosphere. |
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Specifications : |
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Type : |
Pt100, simplex or
duplex |
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Accuracy : |
Class A,
Class B
IEC 751: 1983 |
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Tolerance : |
0.15, 0.06 @
0 Deg C. |
| Alpha : |
0.00385/ DegC |
| Sheath
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SS 304, SS
316, SS 310,
SS 446 |
| Sheath
Dia.: |
6, 8,10, 12,
16, and 22mm |
| Insulation
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Ceramic Beads |
| Head : |
Weatherproof
IP67 Flame
proof suitable
for Gas group
I, IIA & IIB |
| Mounting
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Screwed
connection
or flanged
connection |
| Conn.
Size : |
1/4,
1/2 &
3/4" BSP/NPT |
| Element |
Wire
Wound
Ceramic |
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For Deailed Specs of
Other
Assembly Types Please Contact |
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 Bayonate
RTD
PROBES:
These probes are
available with
enclosed elements
for liquid temp.
Measurement.
Probe extensions are
either straight or
angled to suit difficult
to reach areas.
Probes are supplied with Bayonate fitting coupler
and matching adaptor to mount on application.
Bayonate nut is spring loaded for firm seating of
the measuring tip at the
point of measurement.
Extension leads are either
PVC insulated, PTFE insulated on fibreglass
insulated with SS wire braiding.Terminal ends are
either bare wire with lugs,
miniature socket or BNC
coupler.
Elementsusedare
generally mini ceramic
elements with 1 ot3 mm Dia
x 5 to 15 mm length with
Class B accuracy. |
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Specifications: |
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Type : |
Pt100, simplex or duplex |
| Accuracy : |
Class A,
Class B
IEC 751: 1983 |
| Tolerance |
0.15, 0.06 @
0 Deg C. |
| Alpha |
0.00385 / Deg
C. |
| Sheath : |
SS 304, SS
316, SS 310, SS 446 |
| Sheath Dia. |
1.6, 3, 6 and
8 mm |
| Insulation |
Compacted
MgO. |
| Head : |
Weatherproof
IP67
Flame proof suitable for Gas group I, IIA &
IIB |
| Mounting : |
Screwed
connection
or flanged connection |
| Conn. Size : |
1/4,
1/2 &
3/4" BSP/NPT |
| Element |
Wire Wound
Ceramic |
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Response time for enclosed
element. response for air
probe with exposed element is
30% faster.
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