Honeywell UDC 3300 manual Thermocouple inputs using a precision resistor

Thermocouple inputs using a precision resistor

Referring to Figure 7-3, wire the controller according to the procedure given in Table 7-4.

Table 7-4 Set Up Wiring Procedure for Thermocouple Inputs

Using a Precision Resistor

Step

1

2

3

4

Action

Connect the copper leads to the calibrator.

Disconnect the cold junction resistor.

Install a 500-ohm precision resistor across Input 1 terminals 25 (R) and 27 (–) or Input 2 terminals 22 (R) and 24 (–). See Figure 7-3.

Subtract the millivolt value for 77 °F (25 °C) from the zero and span value for your range (see Table 7-1 for zero and span values) and use the adjusted value when calibrating.

Figure 7-3 Wiring Connections for Thermocouple Inputs

Using a Precision Resistor

			10	1
		L1	11	2
	R	L2/N	12	3
		22	13	4
	+
		23	14	5
Input 2	–
		24	15	6
	R	25	16	7
	+
		26	17	8
	–
Input 1		27		9

Copper Leads Precision 500 Ohm Resistor 1

–

+

Millivolt Source

1Caution: The accuracy of the controller is directly affected by the accuracy of this resistor. At a minimum, use a 0.1%, 25ppm resistor.

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224 UDC 3300 Process Controller Product Manual 4/00