TH51, TH52, TH56
2
Hauser
Function and system design
Measuring principle
The thermocouple sensing element consists of two metal wires that are homogeneous but different from each
other and insulated along their entire length. The two wires are welded together at one end, known as "hot
junction". The other end, where the wires are free, is known as "cold junction" and is connected to an
electromotive force measurement circuit where the force is generated by the different thermoelectric power of
each of the thermocouple wires if there is a temperature difference between the hot junction and the cold
junction (Seebeck effect). The function that links the electromotive force to the temperatures difference is a
curve whose characteristics depend on the materials used in the construction of the thermocouple. The
thermocouples comply with the temperature-electromotive force (EMF) tables of ASTM E-230 and IEC60584
standards.
Measuring system
Example of an application of the temperature assemblies
RIA 261 Field display
The display measures an analog measurement signal and indicates this on the display. The display is connected
in a 4 to 20 mA current loop and also derives its supply from the loop. The volt drop is almost negligible
(< 2.5 V). The dynamic internal resistance (load) makes sure that independently from the loop current, the
maximum volt drop is never exceeded. The analog signal at the input is digitalized, analyzed, and shown in
the rear illuminated display. For details see Technical Information (see "Documentation").
RNS 221
The RNS 221S power supply (24 V DC, 30 mA) has two galvanically isolated outputs for supplying voltage to
loop powered transmitters. The two channel power supply has a wide-range input for main power, 20 to
250 V DC/AC, 50/60 Hz to be used in any electrical circuit. For details see Technical Information (see
"Documentation").
RNS 221 is an UL recognized component to UL-3111-1.
Accessory RMA 421A-VN
NEMA 4x protective housing for field mounting DIN rail instruments, see www.us.endress.com/e-direct.
alpha-Log, RSA10
Universal compact panel mounted color hybrid recorder with 1 to 6 analog inputs, automatic wind up system
for 190 ft. (58 m) roll chart paper and informative dual display concept (analog & digital).
Dimensions: 5.7 x 5.7 x 8.5 inches (144x144x215 mm)
For details see Technical Information (see "Documentation").
Equipment architecture
MgO thermocouple assemblies consists of a thermocouple element swaged in hard-packed standard purity
(96%) Magnesium Oxide mineral insulation and encased in a metal sheath. Thermocouple sheaths have been
fully annealed; they can be formed into many configurations, and can be bent into a radius of twice the size of
its outer sheath. The hot junction of the thermocouple types according to ASTM E-230 specification are welded
to form a pure joint to ensure highest accuracy and long term stability.
