Spectrum Controls 140 AUI 040 00sc - Manual (Page 40)

Quantum Series 140 AUI 040 00sc
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Thermocouples and RTDs are linearized per the following standards:
Thermocouple: per NIST, ITS-90
RTD:
Pt 385: IEC751-1983
Pt 392: JISC1604-1989
Ni 618: DIN 43760
Ni 672: MINCO Application Aid #18, Date 5/90 Type Ni
Cu 426: SAMA RC21-4-1966
Ni/Fe 518: MINCO Application Aid #18, Date 5/90 Type Ni-Fe
RTDs use a switched current source to measure resistance. The settling time for this source has been set so
that RTD inputs will operate properly with a cable length of up to 1000 feet.
Thermocouple inputs require cold junction compensation to acquire accurate data. Thermistors perform cold
junction compensation by measuring the temperature of the terminal block where the thermocouple wire
connects to the terminals. The two CJC headers measure this temperature at the top and bottom of the
terminal block and software interpolates the temperature for all points inbetween. As a simple rule of thumb,
the less temperature difference between the top and the bottom of ther terminal block, the more accurate the
cold junction compensation will be. To achieve the best results it is recommended the module be kept away
from any significant source of heat The CJC headers have been designed for easy installation into the
Quantum universal terminal block as shown in section 5.3. However these thermistors can be installed to a
remote location to provide remote CJC compensation if necessary.
To meet specified accuracy the module should be mounted vertically and the terminal block door should be
closed.