DATA SHEET R-218
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The Series 218, with its 1/8" diameter sheath further supplements the versatile Series 21 RTDs which have a probe diameter of 1/4". The 1/8" diameter offers the advantage of faster response while the strain-free construction, high accuracy and stability offer long-term reliability.

The Series 218 RTDs are versatile and can be used in many different applications. They are offered with premium strain-free wire-wound sensing elements

 

in Reference and International grade platinum having 100 and 200 ohm resistance values with tolerances of ±0.1%. Extra-tight tolerances are available. They are also offered in IEC 751/DIN International Grade B Thin Film Elements. The probes are available in 2, 3, and 4 wire configurations with Teflon® or optional fiberglass insulation.

All Series 218 probes can be used with adjustable compression fittings.
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TYPE
“A”
   
TYPE
“T”
 

Operating Temperature Range
–196°C to 480°C (–320°F to 900°F)
Maximum Operating Temperature
900°F over tip end length.
Note: If lead exit temperature will exceed 260°C (500°F),
please specify on order.
Resistance
See Ordering Specifications Table.
Lead wire resistance to the element is not included
for the 2-wire configuration. The 3-wire and 4-wire
units allow compensation for lead wire resistance.
Temperature Coefficients of Resistance:
0.003924 Ω/Ω/°C (Reference)
0.003850 Ω/Ω/°C (IEC/DIN)
Accuracy
±0.25°C @ 0°C (32°F)
±0.3°C @ 0°C (32°F)
on IEC/DIN thin films

Stability
Less than 0.05°C shift per year full span on wire elements
–50°C to 300°C (–60°F to 500°F) span on thin films
Self-Heating
75 mW/°F in water flowing at 3 ft. per sec.
Pressure Rating
3000 PSI at welded header boundary
Insulation Resistance
500 Megohms minimum @100 VDC at room temperature
Time Constant
Less than 2 sec, in water flowing at 3 ft. per sec.
Standard Leads
22 AWG stranded, nickel plated copper, Teflon® insulated, except 3-wire leads on type “A” are 28 AWG.
3 or 4-wire leads over 36" are cabled on type “T”.
Type “A” 3-wire leads over 36" are not cabled unless designated for operation below 500°F.
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   TYPE   1/8" diameter Platinum RTD Probes (316 stainless steel)
   218A    Straight Sheath
   218T    Straight Sheath with 1" long x 1/4" Diameter Transition

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   RTD RESISTANCE SPECIFICATION (ohms @ O°C)
   10     100   ±0.1Ω   Strain Free wire-wound 0.003924 Ω/Ω/°C (RdF Reference Grade)
   11     100   ±0.1Ω   Strain Free wire-wound 0.00385 Ω/Ω/°C (IEC/DIN)
   20     200   ±0.2Ω   Strain Free wire-wound 0.003924 Ω/Ω/°C (RdF Reference Grade)
   21     200   ±0.2Ω   Strain Free wire-wound 0.00385 Ω/Ω/°C (IEC/DIN)
   T01    100   ±0.12Ω  Thin Film 0.00385 Ω/Ω/°C (IEC/DIN Grade B)
   T05    500   ±0.6Ω   Thin Film 0.00385 Ω/Ω/°C (IEC/DIN Grade B)
   T10    1000  ±1.2Ω   Thin Film 0.00385 Ω/Ω/°C (IEC/DIN Grade B)		 _
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 PROBE LENGTH
  Specify “L” in inches (3" minimum on wire-wound only; 1" on thin films)		 _
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  NUMBER OF LEADS
     A      single element, 2 wires any length
     B      single element, 3 wires 36" or under in length
     C      single element, 4 wires 36" or under in length (Not available on type “A”)
     X3     single element, 3 wire cable over 36" (on Type “A”, only for operation below 500°F)
     X4     single element 4 wire cable over 36" (Not available on Type “A”)		 _
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   LEAD LENGTH - Inches (6" standard) _
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218A
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10
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6
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A
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24
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- Typical write-up for 218A

Adjustable Compression Fitting
   Part
   Number
 Process
Mounting
Material		 Sensor Sheath
Diameter
  51841-1 1/8 NPT Stainless Steel 0.125
  51841-2 1/4 NPT Stainless Steel 0.125
  51841-3 1/4 NPT Stainless Steel 0.25 (transition)
  51841-4 1/2 NPT Stainless Steel 0.25 (transition)
 
RdF Corporation • 23 Elm Ave., Hudson, NH 03051  
800.445.8367 • 603.882.5195 • fax 603.882.6925 • www.rdfcorp.com