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Thermister electrical resistance values can
range from 100 to 1,000,000 ohms at 25°C. The resistance
change is approximately -4.4% per °C at 25°C. The large
resistance change limits thermistors to narrow temperature ranges
and low temperatures. However, in these situations, thermistors
have greater accuracy and ambient temperature stability than
RTDs or thermocouples. Lead wire can be as long as 1,000 feet
without significant error.
Platinum RTD's electrical resistance values
change approximately .385% per °C. The DIN standard element
is 100 ohms at 0°C, showing a nearly linear change of + 38.5
ohms between 0 and 100°C. Platinum RTDs provide very good
system accuracy at very low temperatures to 1000°F. Two wire
RTDs have significant errors when over 10 feet long. However,
these errors can be eliminated by using 4 wire RTDs.
Thermocouples re constructed of two wires
of dissimilar metals that generate .05 MV per °C at the "hot"
junction. The "cold" junction must be maintained temperature
constant by electronic means to avoid signal errors. Low signals
and linear complexities make system accuracy and integrity difficult.
However, thermocouples respond to temperature changes very quickly,
are virtually impervious to vibration or other mechanical conditions,
have a wide range and high temperature capability.
Adaptor Plates for Mounting
Smaller Size Controls in Larger Openings
PMAE-1: 1/4
DIN opening to 72MM
PMAE-2: 1/4 DIN opening to 1/16 DIN
PMAE-3: 1/4 DIN opening to 1/8 DIN |
PMAE-4: 1/8 DIN
opening to 1/16 DIN
PMAE-5: B/C 520- to 1/8 DIN
PMAE-6: 72mm opening to 1/16 DIN |
Other size adaptors
availableConsult Ogden
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