JUMO 202755, Руководство по эксплуатации

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13 Eliminating faults and malfunctions
62
13.1.1 Resistance loop test
Position of the
resistance loop
✱
Lead a wire through the cell (see diagram)
✱
Connect a resistor R to the wire
Calculating the
resistance Formula for calculating the resistance of the resistance loop:
Note: 1 mS/cm = 1·10
-3
S/cm
1 µS/cm = 1·10
-6
S/cm
For display values up to 49 mS, the loop must have 1 turn.
For display values above 50 mS, the loop must have 3 turns.
Example 1 The measuring transmitter is to show 20 mS:
To achieve a display of 20 mS/cm, the resistance loop (with 1 turn) must have
a resistance of 312.5 Ohm.
During calibration, do not touch the sensitive part of the cell or put
it down on any surface, otherwise the measurement will be
falsified.
R
R =
N
2
· K
R = Resistance of the resistance loop
Lf N = No. of turns in the loop
K = Cell constant
Lf = Required display in S/cm
The cell constant of the device is 6.25 1/cm.
R =
1
2
·6.25 1/cm
= 312.5
Ω
20·10
-3
S/cm
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