Future Design MCT-CM, User Manual

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MCT-CM
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The Low Scale and High Scale fields are shown for analog input types only. They are used to set the display
range for the input in order to scale the 0(2)-10Vdc or 0(4)-20mA signal. The display value is then a linear
representation of the input signal from the low to high scale value.
Once all of the settings have been made for the monitor point, press the
“Done” button to return to the Monitor
Setup screen.
4.3.1.1 Important Settings for Using Loop Input 2 as Monitor Points
Decimal Point When using the second input of control loops for monitor points, it is important to note
that the controller itself, provides range, calibration and input bias settings for the input.
In order for the MCT to properly read and display the value, the decimal point setting for
the monitor input must match that of the loop control for input 2. If the decimal point
settings do not match between the MCT and the loop controller, the MCT will not properly
read or display the value of the second input for the monitor point.
Engineering Units
When degrees C or degrees F is selected from the Degrees C/F screen in the MCT
runtime application, engineering units for temperature of
“C” or “F” are automatically
updated for all loop and monitor points. If input 2 of the loop controller is a temperature
reading in degrees F for example (from a temperature transmitter), and degrees C is
selected on the MCT, the monitor point reading will be a value in degrees F, but the units
shown will be in degrees C.
To prevent the units from being changed, the Degrees C/F settings screen in the runtime
application can be hidden to prevent changes (see section 4.7 Functions) or even
password protected in the runtime application. The engineering units could also be
entered as
“degC” or “degF” for example. The MCT will then ignore them for a degrees
C or degrees F units change.
It is important to ensure that the engineering units match the loop control for input 2 to
avoid operator confusion and prevent the misinterpretation of the value.
Input Offsets When using the second input of control loops for monitor points, it is important to note
that the controller itself, provides range, calibration and input bias settings for the input.
The MCT does provide an input offset capability which can be used to correct errors in
readings from the analog, RTD or thermocouple monitor modules in order to correct for
lead resistance or sensor tolerance.
The
“Input Offset” screen in the MCT runtime application also allows an offset to be
applied to the monitor points when input 2 of the loop controls are used. However, the
input offset of the MCT only corrects the value shown on the MCT and does not offset
the reading on the loop control.
If the loop control is visible to the operator, it is recommended that the
“Input Offset”
screen be hidden (see section 4.7 Functions) or even password protected in the runtime
application to prevent an offset from being applied to the monitor point in the MCT.
Rather, use the input bias setting of the loop control so that both the reading on the loop
control and the MCT will match to avoid operator confusion.