Table of Contents
Diagnostics and troubleshooting
For example, start with a simulated resistance of 103.9 Ω, which corresponds to 10.0 °C
(50 °F). Assume that 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 (68 °F). 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.
Temp
1 °C (34 °F)
10 °C (50 °F)
20 °C (68 °F)
25 ° C (77 °F)
30 °C (86 °F)
40 °C (104 °F)
50 °C (122 °F)
60 °C (140 °F)
70 °C (150 °F)
80 °C (176 °F)
85 °C (185 °F)
90 °C (194 °F)
100 (212 °F)
8.4.13
Measuring reference voltage
Some processes contain substances that poison or shift the potential of the reference
electrode. Sulfide is a good example. Prolonged exposure to sulfide converts the reference
electrode from a silver/silver chloride electrode to a silver/silver sulfide electrode. The
change in reference voltage is several hundred millivolts. A good way to check for
poisoning is to compare the voltage of the reference electrode with a silver/silver chloride
electrode known to be good. The reference electrode from a new sensor is best. See
Figure
than about 20 mV. A poisoned reference electrode usually requires replacement.
118
8-16. If the reference electrode is good, the voltage difference should be no more
Pt 100 (Ω)
100.0
103.9
107.8
109.7
111.7
115.5
119.4
123.2
127.1
130.9
132.8
134.7
138.5
22k NTC (kΩ)
64.88
41.33
26.99
22.00
18.03
12.31
8.565
6.072
4.378
3.208
2.761
2.385
1.796
Rosemount 5081
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- 5081 Programming
- Manual Calibration
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Table of Contents
Troubleshooting
