IM 12B6C2-E-H
1. What is the Output-range?
The display will always show the actual value
between -1 and 15 pH.
The output range is a linear function of mA
versus pH and is fixed by two points.
As the output is fixed to 4..20 mA the two
points of the linear function have to be pro-
grammed to set the range.
The factory setting is a full range of 0..14pH.
Any value between -1.. + 15 pH is accepta-
ble for both points. A minimum span of 1
unit must be kept.
An error E19 will point to not acceptable
values.
NOTE:
1. The linear output signal is limited to 3.9 to
20.5 mA giving a safety area of 2.5% at
both ends.
2. Values below 3.9 or above 20.5 mA are
not related to input values and signal a
malfunction.
2. How to adjust?
EXAMPLE:
The EXA PH200 has to be programmed for
a range of 2 ... 12 pH.
Adjust 4 mA to 2.00 pH
Adjust 20 mA to 12.00 pH
The instrument will now correct its calcula-
tion for the output signal accordingly.
3. Calculation example
The current to be set at the output is calcu-
lated as follows:
pH - pH
min
mA = x 16 + 4
pH
max -
pH
min
pH = actual value
pH
min
= value at 4 mA
pH
max
= value at 20 mA
pH
max
- pHmin = span (≥ 1 pH)
It is advisable to choose a span devisable by
10, 5 or 2 for easy reading on scales.
4. Other possibilities
Set a 22 mA signal on the output, when
FAIL is on (see §7-7).
13
4-2. Output range adjustment
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