Tri-Linear - Hach ORBISPHERE G1100 User Manual

The formula to compute the measurement knowing the current I (or voltage U) and the
resolution R is given in the following table:

8.5.2 Tri-linear

The "Tri-linear" output brings benefits over the "Linear output" discussed before. It is illustrated
in Figure 38
Compared to the "Linear" mode, the expected range of measure is Range 2. A Range 1 and 3
are available to show the measures falling out of this Range 2, but normally at a lower
resolution. Expected measurements for the measured process are supposed to be in Range 2
most of the time, and in Range 1 or 3 occasionally (problems, calibration, line stop, etc.). The
benefits are:
The PLC can compute the measurement over a large range (1, 2 and 3).
•
The PLC can compute a higher resolution signal for the expected measuring range (Range
•
2: MH > M > ML).
Carefully selecting the set points allows for an individual resolution for each range, so a
•
different resolution can be applied to Range 1, 2 and 3, allowing to tailor the analog output to
the actual conditions.
As before, the downside is that any measure below or over the Range 1, 2 and 3 will have the
same signal locked at 4 mA and 20 mA respectively, but Range 1, 2 and 3 should cover a larger
range than in the "Linear" mode. Settings must made in balancing these aspects.
Settings
For each output, set MLL, ML, MH, and MHH in the current measuring unit (e.g. °C for a
temperature output). When a compound unit is selected, the smallest unit will be used (e.g. ppb
for a "ppm-ppb" compound unit). Also set AOL (Analog Output Low) and AOH (High) in mA (or
Volts).
Linear Range
4-20 mA 20 > I > 4
0-20 mA 20 > I > 0
0 - 5 V 5 > U > 0
below (4-20 mA output is shown, 0-20 mA or 0-5 V settings are similar).
Figure 38 "Tri-linear" characteristics diagram (4-20 mA shown)
Measurement M
M = ML + (MH - ML) (I - 4) / 16
*
M = ML + (MH - ML) I / 20
*
M = ML + (MH - ML) U / 5
*
Inputs/Outputs Menu
Resolution R
R = (MH-ML) / 808
R = (MH-ML) / 1010
R = (MH-ML) / 1010
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