| 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 |
