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Section 7. Installation
347
Measuring Multiple PRTs (PT100 Resistance() Basic-Circuit Series)
If you connect only one PRT to a [
U
] [
Ix
] terminal configured for current
excitation, the previous procedure serves well. However, if multiple PRTs are
measured from a single excitation terminal, the sum of voltages output from all
PRTs connected to one excitation terminal must not exceed 5000 mV, which is
the input limit (InLim) for the CR6. This limitation also serves to limit the
current load on the excitation terminal.
Calculate the maximum number of PRTs for one excitation terminal. Do this by
calculating IX
max
at several PRT numbers:
IX
max
= ((InLim / (n • RS
min
)) • 0.99
where,
InLim = Input Limits = 5000 mV
n = number of PT100 sensors
RS
min
= minimum resistance in the temperature range = 84270 mΩ
so,
IX
max
= 0.029 mA (29 µA) when n = 2
Other results are tabulated in the following table.
Number of PT100
PT100 Number, (n)
Max Excite Current, (IX
max
)
1
0.059 mA
2
0.029 mA
3
0.020 mA
4
0.015 mA
5
0.012 mA
6
0.010 mA
When using a current excitation greater than 1 mA, self-heating of the PRT
element becomes a problem. Having your temperature sensor heat itself is far
from desirable! You can reduce self-heating by minimizing the
SettlingTime
and
Integ
parameters in the
Resistance()
instruction, and by minimizing measurement
frequency, perhaps by increasing the
Scan()
interval.
Содержание CR6 Series
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Страница 76: ...Section 5 Overview 76 FIGURE 20 Half Bridge Wiring Example Wind Vane Potentiometer ...
Страница 80: ...Section 5 Overview 80 FIGURE 23 Pulse Input Wiring Example Anemometer ...
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Страница 251: ...Section 7 Installation 251 FIGURE 46 Running Average Frequency Response FIGURE 47 Running Average Signal Attenuation ...
Страница 454: ...Section 8 Operation 454 FIGURE 104 Narrow Sweep High Noise ...
Страница 459: ...Section 8 Operation 459 FIGURE 106 Vibrating Wire Sensor Calibration Report ...
Страница 535: ...Section 8 Operation 535 8 11 2 Data Display FIGURE 121 CR1000KD Displaying Data ...
Страница 537: ...Section 8 Operation 537 FIGURE 123 CR1000KD Real Time Custom ...
Страница 538: ...Section 8 Operation 538 8 11 2 3 Final Storage Data FIGURE 124 CR1000KD Final Storage Data ...
Страница 539: ...Section 8 Operation 539 8 11 3 Run Stop Program FIGURE 125 CR1000KD Run Stop Program ...
Страница 541: ...Section 8 Operation 541 FIGURE 127 CR1000KD File Edit ...
Страница 542: ...Section 8 Operation 542 8 11 5 PCCard Memory Card Management FIGURE 128 CR1000KD PCCard Memory Card Management ...
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Страница 549: ...Section 9 Maintenance Details 549 FIGURE 133 Separate Back Shell from Module FIGURE 134 Disconnect Battery Connector ...
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Страница 610: ...Section 11 Glossary 610 FIGURE 137 Relationships of Accuracy Precision and Resolution ...
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