BEAMEX MC5-IS - Resistance and RTD Measurement, Connections; 4-Wire System

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Resistance and RTD Measurement, Connections

The two main problems in resistance and RTD measurement are

the effects of wiring resistances and thermovoltages in the resis-

tance measurement circuit. If possible, use 4-wire connection to

eliminate the effect of wiring resistance. The special resistance

measurement sequence of MC5-IS eliminates the thermovoltages

of the resistance measurement circuit.

MC5-IS continuously checks the connection type during resistance

and RTD measurement. The found connection type is displayed

on the resistance or RTD measurement window.

3-wire System

MC5-IS sources current through the resis-

tor from the two left side terminals. MC5-

IS measures the voltage drop across the

entire current loop and across the low side

connection wire. If both left side connec-

tion wires are identical, MC5-IS can com-

pensate for the resistance of the connec-

tion wires.

4-wire System

MC5-IS sources current through the resis-

tor from the two left side terminals. MC5-

IS measures the voltage drop across the

resistor from the two right side terminals.

The 4-wire method gives the resistance

between the terminals of the resistor, it is

insensitive to the resistance of the con-

nection wires.

R, RTDT/C, Low V

HART

meas/sink

V, ,

sink

Com

R, RTD

Low V

MEASUREOUTPUT

ET E

T/C INT. RJ

SENSOR MEASURE & SIMULATE

Uo: 16 V

Io: 24 mA

Po: 145 mW

T/C

WIRES

ONLY

4 w meas

3 w measmeas/sim