Emerson PN 51-FCL-1056 instruction manual Simulating Inputs Temperature, Simulating temperature

MODEL FCL-1056

9.10 SIMULATING INPUTS — TEMPERATURE

9.10.1 General.

The analyzer accepts a Pt100 RTD (for pH and chlorine sensors). The Pt100 RTD is in a three-wire configuration. See Figure 9-5.

9.10.2 Simulating temperature

To simulate the temperature input, wire a decade box to the analyzer as shown in Figure 9-6.

To check the accuracy of the temperature measurement, set the resistor simulating the RTD to the values in the table and note the temperature readings. 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 temperature 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 tempera- tures 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 cal- culate the temperature, so the display reads 19.2°C. Because the difference between the displayed tempera- tures (10.0°C) is the same as the difference between the simulated temperatures, the analyzer is working correctly.

SECTION 9.0

TROUBLESHOOTING

FIGURE 9-5. 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 with temperature.

FIGURE 9-6. 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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