Burkert Type 8620 - Manual (Page 97)

mxCONTROL Type 8620
Page 97
Maximum Output Timer (MOT)
This function monitors the controller output in automatic mode. If the controller output puts out the
100% control output longer than the defined max. output time (+Tm), the "Out fails" alarm is put out
and the general alarm output is enabled.
The internal timer which counts the period of the max. control output is reset if the control output
equals 0% and the alarm has not yet been triggered.
The Maximum Output Timer can be enabled/disabled via configuration. For a general description of
the MOT refer to chapter 14.1.5.
Total Dissolved Solids (TDS)-Display
The TDS display indicates the total content of dissolved solids of the conductivity process value (e.g.
the boiler water) in ppm. The concentration is calculated by correlating values from a diagram (see
Figure 38) to the measured conductivity values (measured in μS/cm):
TDS = C * S
with C …… Measured conductivity value
S …… Slope of the graph (the factory setting is 0.8)
Since the relationship between Conductivity and TDS is essentially a linear relationship, it is
possible for the controller to display TDS by converting the conductivity input information into TDS
units (ppm). This conversion is possible by reference to graph in Figure 38 which is held in memory.
Note! The slope of the curve can be adjusted by the operator more closely to actual boiler water
conditions.
Chemical analysis of the boiler water will establish the precise relationship between conductivity and
TDS for a particular combination of factors. With these values the slope of the calibration graph can be
adjusted, by entering values for Conductivity (PV cal) and TDS (TDS cal) in the "Parameter"
menu item.
Specific Conductance to TDS conversion table for Slope = 0.8
0
1000
2000
3000
4000
5000
6000
7000
8000
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Conductivity in µS/cm
T
D
S
in
ppm
Figure 38:
Relationship
between conductivity
and TDS
The controller output will not be influenced by the alarm. The alarm message has to be
acknowledged by the operator on the device, even if the operating mode was changed.