Yokogawa AXFA14G/C - Manual (Page 23)

IM 1E6K2-E
4-19-15
4. OPERATION
(2) Enhanced dual frequency excitation
When the AXFA14 is used in combination with the AXF flowtube which supports the
enhanced dual frequency excitation (optional code HF1 or HF2), the calibration of that
excitation is necessary.
In case of AXF integral flowmeter which supports the enhanced dual frequency
excitation (optional code HF1 or HF2), the calibration of that excitation is necessary.
Change Function.
Turn on tne Junction box power.
Span setting
Changing the setting of AXF AMPLIFIER UNIT
Check the zero point
Set the “MEASURE_MODE” parameter of TR Block to “Enhanced DF”. (Before
changing the mode, write down the previous value)
Set the meter factors of “LOW_MF (EDF)” and “HIGH_MF (EDF)” parameters of TR Block to
1.0000. (Before changing the settings, record the previous values.)
Slide the AM012 FUNCTION switch to the ADMAG posiotion.
Two excitation lamps will flash alternately at regular intervals. (See Note 1 below)
After turning on the power, let the instrument warm up for at least three minutes.
Set the flow velocity of the span with the AM012 span dial. Firstly, be sure to confirm that the
"NOMINAL_SIZE_UNIT" parameter of TR Block is set to "mm". The flow velocity can be
checked with "VELOCITY_CHECK" parameter of the TR Block of the converter.
Turn the output knob of AM012 to 0% to check the zero point. To check the span accurately, record
the indicated value. (See Note 2 below)
Check the span and output accuracy
Return the ADMAG AXF AMPLIFIER UNIT set values to their initial values.
Return the "MEASURE_MODE" parameter of TR Block to the initial value which was previonsly
recorded.
Return the two meter factors of "LOW_MF" and "HIGH_MF" parameters of TR Block to the
value recorded before the change.
Turn off the Junction box power.
Turn the output knob to 25%, 50%, 75% and 100% in turn and check the indicated values by
confirming "OUT" parameter of AI Block. (Subtract the zero point value from the indicated value to
check the output accuracy.) Set the knob to CHECK to check the common mode noise rejection.
(See Note 3 below)
Remove the power supply and ground cables from the AM012.
Remove the signal and excitation cables from the AM012.
Remove the amplifier unit from the Junction box .
Install the amplifier into the converter.
Disconnect from the Host
Loosen the fixing screws, disengage the connectors, then remove the amplifier unit.
Refer to the explanation of "Install the amplifier into the converter" in 4.9.2 (1).
End
Note 1 : If no exciting current flows, the two excitation lamps do not flash correctly.
Note 2 : When the zero readjustment is available (i.e. the flowtube has been filled with fluid and the fluid velocity is
completely zero) after checking of AXFA14 or AXF integral flowmeter, it is convenient to carry out zero
adjustment instead of subtraction the zero point value.
In case that zero readjustment is not available, do not carry out zero adjustment of AXFA14 or AXF integral
flowmeter.
Note 3 : A common mode noise signal equivalent to a set value with the span-setting dial is output from the AM012.
Note 4 : In case of parameter change via the Host, set the MODE_BLK of each parameter to O/S mode before the
change. (Refer to IM 01E20F02-01E page A-2.)