Emerson ROC827 instruction manual Wiring United States Color Coding, Sheathed, Module to ground

ROC827 Instruction Manual

Noise Susceptibility Millivolt signals are very small and are very susceptible to noise. Noise from stray electrical and magnetic fields can generate voltage signals higher than the millivolt levels generated from a thermocouple. The T/C modules can reject common mode noise (signals that are the same on both wires), but rejection is not perfect, so minimize noise where possible.

Take care to properly shield thermocouple wiring from noise by separating the thermocouple wiring runs from signals that are switching loads and AC signals. Route wires away from noisy areas and twist the two insulated leads of the thermocouple cable together to help ensure both wires pickup the same noise. When operating in an extremely noisy environment, use a shielded extension cable.

+	+
–	–
TypeJus.dsf	TypeKus.dsf
Figure 4-16. Type J Thermocouple Shielded	Figure 4-17. Type K Thermocouple Shielded
Wiring – United States Color Coding	Wiring – United States Color Coding

United States color-coding for the Type J Thermocouple shielded wiring is black sheathing, the positive lead is white, and the negative lead is red.

United States color-coding for the Type K Thermocouple shielded wiring is yellow sheathing, the positive lead is yellow, and the negative lead is red.

Caution	Shielded wiring is recommended. Ground shields only on one end,
	preferably at the end device unless you have an excellent ground system
	installed at the ROC800-series controller. Do not tie the thermocouple
	module to ground.

Note: It is highly recommended that you use shielded wiring.

Sheathed thermocouple probes are available with one of three junction types: grounded, ungrounded, or exposed.

unground.dsf	ground.dsf	exposed.dsf
Figure 4-18. Ungrounded –	Figure 4-19. Grounded	Figure 4-20. Exposed,
Sheathed		Ungrounded – Unsheathed

In an ungrounded probe, the thermocouple junction is detached from the probe wall. Response time slows down from the grounded style, but the ungrounded probe offers electrical isolation of 1.5 M ½ at 500 Volts dc in all diameters. The wiring may or may not be sheathed.

Issued Mar-06 Input/Output Modules 4-19