Mettler Toledo M400 Guia De Inicio Rapido página 23

20.9
B
%V O2
20.9
B
%Trm
Pressure=External
20.9
B
%V O2
20.9
B
%Trm
Ain 4mA = 940.0 mbar
Ain 20mA = 2000. mbar
20.9
B
%V O2
20.9
B
%Trm
Pressure=fixed
20.9
B
%V O2
20.9
B
%Trm
Pressure=1013. mbar
20.9
B
%V O2
20.9
B
%Trm
Temperature=External
– Fixed: p ressure compensation uses a fixed value to be set manually.
Note: if this pressure compensation mode is selected, a considerable
gas concentration measurement error resulting from a non- realistic
pressure value can take place.
If External compensation is selected, then the minimum (4 mA) and maximum
(20 mA) analog output signals from the pressure transducer must be mapped to the
corresponding Analog input of the TDL. key in the minimum and maximum values
of the pressure in the following units:
u
– hPa – mmHg
– psi – kPa
In general, METTLER TOLEDO recommends the use of absolute pressure transducers
for more accurate signal compensation over a broad pressure range. If, however,
small pressure variations around atmospheric pressure are to be expected, relative
pressure sensors will produce better results; but the variations of the underlying
u
barometric pressure will be ignored.
For relative pressure sensors, the minimum and maximum values must be mapped
so that the TDL can interpret the analog pressure signal as "absolute", i.e. a fixed
barometric pressure of 1013 mbar (for example) has to be added to the mapped
values.
If Fixed compensation is selected, the fixed pressure value with which the measure-
ment signal will be calculated has to be keyed in manually. For the fixed pressure,
the following units can be used:
– hPa – mmHg
u
– psi – kPa
u
If External compensation is selected, then the minimum (4 mA) and maximum
(20 mA) analog output signals from the temperature transducer must be mapped to
the corresponding Analog input of the TDL. key in the minimum and maximum
values of the temperature in °C.
u
– mbar
– mbar
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