BEKA BA574C, Руководство пользователя

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It is preferable to make this substitution as close to
the RTD as possible, but if necessary the
transmitter may be calibrated in a workshop.
Select '4rtd' from the 'Cond' sub-menu and press
P.
The transmitter will display scrolling decimal points
while the reference is being updated followed by
'Ent' prior to returning to the '4rtd' prompt. This
completes adjustment of this reference.
5.8.5 Output current reference 'OP'
Warning: ensure plant safety
before performing this adjustment
This adjustment is only necessary if the transmitter
4/20mA output current is used. A method of
accurately measuring the transmitter output current,
such as DVM, is required to calibrate this
reference.
Select 'OP' from the 'Cond' sub-menu and press P ,
the transmitter will display 'SurE'. If it is safe to
change the transmitter output current between 4
and 20mA continue by pressing
P . The transmitter
will display 'ZEro', pressing P again will change the
display to '.004A' and the transmitter output current
to approximately 4mA. The transmitter output
current shown on the external current measuring
instrument should be adjusted to 4.000 ±0.001mA
using the transmitter
Up and Down buttons. When
correct press the E push-button to return to the
'ZEro' prompt.
To adjust the 20mA output current reference select
the 'SPAn' prompt by operating the
Up or Down
button. Pressing P will change the display to
'.020A' and the transmitter output current to
approximately 20mA. The transmitter output
current shown on the external current measuring
instrument should be adjusted to 20.000± 0.001mA
using the transmitter
Up and Down buttons. When
correct press the E push-button twice to return to
the 'OP' prompt. This completes adjustment of this
reference.
6. TRIM MENU
The Trim Menu enables the BA574C transmitter to
be adjusted using an external voltage, resistance or
temperature calibrator. For maximum accuracy the
complete loop including the thermocouple or
resistance thermometer may be calibrated by
heating or cooling the primary element.
Before using the Trim Menu all the functions in the
'InPut' and 'CAL' sections of the programme menu
must be defined, including the 4/20mA output
range, and for voltage inputs the input and display
ranges.
If a voltage calibrator is used to simulate a
thermocouple the transmitter cold junction
compensation must be turned off. Alternatively, the
temperature at the BA574C input terminals may be
measured and the voltage calibrator corrected for
ambient temperature, although this is likely to
produce less accurate results.
6.1 Calibration procedure using Trim Menu
The structure of the Trim Menu is shown in Fig 7.
Access to the menu is obtained by operating the
P
and Down push-buttons simultaneously. If the
transmitter is not protected by a security code the
first parameter 'ZEro' will be displayed. If the
transmitter is protected by a security code, 'COdE'
will be displayed first. Pressing
P again will enable
the security code to be entered digit by digit, using
the
Up and Down buttons to change the flashing
digit, and the P push-button to move to the next
digit. If the correct code is entered pressing E will
cause the first parameter 'ZEro' to be displayed.
If an incorrect code is entered, or if no button is
pressed for ten seconds, the transmitter will
automatically return to the display mode.
Fig 7 Trim Menu
The 'ZEro' sub-menu allows the transmitter display
and output current to be independently trimmed at
the bottom of the input range. To make the adjust-
ment connect a calibrator to the transmitter input
terminals to simulate minimum input, or place the
primary element in a vessel at the minimum
temperature. With 'ZEro' displayed, pressing the
P
push-button will cause the temperature display to
return.
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