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ifm Programming Manual ecomatmobile BasicController (CR0403) Runtime System V03.02 2015-04-01
System description Hardware description
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Resistance measurement
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Typical sensors on these inputs:
• tank level
• temperature (PT1000, NTC)
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Figure: block diagram of the resistor survey input
In = pin resistor survey input n
(CR) = device
(1) = input filter
(2) = constant-current source
(3) = voltage
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The resistance for this device is not linearly dependent on the resistance value, → figure:
Figure: resolution dependent on the
resistance value
(1) = resistance value at the input
(2) = resolution
By how many ohms does the measured value change when the signal of the A/D converter on the input changes by 1?
Examples:
• In the range of 1...100 Ω the resolution is 1.2 Ω.
• In the range of 1 kΩ the resolution is approx. 2 Ω.
• In the range of 2 kΩ the resolution is approx. 3 Ω.
• In the range of 3 kΩ the resolution is approx. 6 Ω.
• In the range of 6 kΩ the resolution is approx. 10 Ω.
• In the range of 10 kΩ the resolution is approx. 11 Ω
• In the range of 20 kΩ the resolution is approx. 60 Ω.
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