Version: TCM_0450_E80_M_EN_150209_E007
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General Information
1.4.
Measuring Principle TCM
Two parallel flow tubes inside the TCM Flow Meter are vibrating at their natural frequency in opposite direction.
Any mass flow passing through the tubes will delay the vibration at the incoming side and accelerate the
vibration at the outgoing side. This causes a small time shift between both ends of the tube. This time shift is
measured and used to calculate the mass flow through the tubes.
By measuring the natural frequency of the tubes the density of the medium can be calculated.
As both effects are temperature dependent, the temperature is measured by means of an accurate temperature
sensor for correcting the temperature effects on flow and density measurement.
As a result a Coriolis Mass Flow Meter measures directly mass flow, density and temperature of the medium.
Knowing the mass flow and the density, also the volume flow can be calculated.
Fig. 2: Principle of operation Coriolis Mass Flow Meter
1.5.
Custody Transfer
When the
“Custody Transfer” option is selected, the following restrictions apply:
Due to an additional Modbus command filter (additional electronic component), only a few parameters that
are not critical for measuring can be written via Modbus (see the document:
“Modbus (RTU) Manual”:
chapter 3.5). Read access to all values that can be read via Modbus remains unchanged from the standard
version.
The speed of the Modbus interface is fixed at 57600 baud and cannot be changed by the user.
As soon as critical events (error messages) are written to the log, this is indicated by alternate flashing of the
red and green LEDs until the user performs a manual reset (see chapter 4.3.5).
The P button on the display cannot be operated with the magnet any more when the front cover is closed.
This means no more device settings can be changed when the housing is closed and sealed.
The two housing covers as well as the plug-in connections of the connecting cable must be secured with
suitable seals to prevent unauthorized opening or unplugging.
In case of a critical error state, all measured flow rate values are accumulated in a failure total counter (FAIL.
TOTAL) instead of the totalizer (GRAND TOTAL) as long as the error state remains active.
The standard displays have the following fixed two-line configuration:
-
Standard display: 1st line:
“Current mass flow” + 2nd line: “Totalizer”
-
Alternative display: 1st line:
“Tempe 2nd line “Failure Total Counter”
Remote control is possible exclusively via RS485/Modbus RTU
(HART® or Foundation Fieldbus® are permanently inactive)
The control input (CTRL IN) is permanently inactive (=OFF)
