Emerson TCL instruction manual Simulating Temperature, Simulating temperature

MODEL TCL

11.6 SIMULATING TEMPERATURE

11.6.1 General.

The Model 1056 accepts a Pt100 RTD. The Pt100 RTD is in a three-wire configuration. See Figure 11-3.

11.6.2 Simulating temperature

To simulate the temperature input, wire a decade box to the analyzer or junction box as shown in Figure 11-4.

To check the accuracy of the temperature measure- ment, set the resistor simulating the RTD to the values indicated in the table and note the temperature read- ings. The measured temperature might not agree with the value in the table. During sensor calibration an offset might have been applied to make the measured tem- perature agree with a standard thermometer. The offset is also applied to the simulated resistance. The analyzer is measuring temperature correctly if the difference between measured temperatures equals the difference between the values in the table to within ±0.1°C.

For example, start with a simulated resistance of 103.9 Ω, which corresponds to 10.0°C. Assume the offset from the sensor calibration was -0.3 Ω. Because of the offset, the analyzer calculates temperature using 103.6 Ω. The result is 9.2°C. Now change the resistance to 107.8 Ω, which corresponds to 20.0°C. The analyzer uses 107.5 Ω to calculate the temperature, so the display reads 19.2°C. Because the difference between the displayed temperatures (10.0°C) is the same as the difference between the simulated temperatures, the analyzer is working correctly.

SECTION 11

TROUBLESHOOTING

FIGURE 11-3. Three-Wire RTD Configuration.

Although only two wires are required to connect the RTD to the analyzer, using a third (and some- times fourth) wire allows the analyzer to correct for the resistance of the lead wires and for changes in the lead wire resistance caused by temperature changes.

FIGURE 11-4. Simulating RTD Inputs.

	Temp. (°C)	Pt 100 (Ω)
	0	100.0
	10	103.9
	20	107.8
	25	109.7
	30	111.7
	40	115.5
	50	119.4
	60	123.2
	70	127.1
	80	130.9
	85	132.8
	90	134.7
100		138.5

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