BEKA BA578C, Руководство пользователя

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When the transmitter display is correct, press P
which will lock the transmitter display and, after
briefly displaying 'Ent', allow the 4/20mA output
current to be trimmed using the
Up or Down push-
button. Again the output current should be
measured with an accurate DVM or another instru-
ment within the loop. Operate the
Up or Down
buttons until the required output current is shown on
the DVM or other instrument. When correct, press
the
E button to store the trim correction in perma-
nent memory and return the BA578C transmitter to
the 'SPAn' prompt. This completes re-calibration
of the BA578C transmitter at maximum input.
When calibrating the BA578C using the Trim Menu
both the zero and span must be adjusted.
The Trim Menu contains a clear function which
enables the small calibration correction made with
the 'ZEro' and 'SPAn' sub-menus to be removed.
To clear the corrections select 'CLr' from the Trim
Menu and press
P. The display will show 'Ent' for a
short while and then return to the ''CLr' prompt.
6.2 Periodic re-calibration using Trim Menu
The Trim Menu is the best way of making small
calibration adjustments to compensate for any long
term drift which may occur. Initially an annual
check is recommended to achieve maximum
accuracy, although less frequent checks will usually
produce acceptable results.
If the BA578C internal references are used to make
frequent calibration changes, we recommend that
these references should be initially checked once
per year as described in section 5.8 If the
BA578C is always calibrated with an external
reference, such as a voltage source using the Trim
Menu, it will not be necessary to check the internal
references.
7. CALIBRATION EXAMPLE
In this example a BA578C is required to display
with maximum resolution the temperature of a type
J thermocouple, and to transmit a 4/20mA signal
representing -10 to 240
o
C. If the thermocouple
breaks the 4/20mA output current is to rise to full
scale. The current security code is 1209.
The example is divided into two sections. Steps 1
to 10 explain how to condition the transmitter and to
calibrate the 4/20mA output using the internal
references. This will produce acceptable accuracy
for most applications, but will not compensate for
errors in the thermocouple or load connected to the
4/20mA output
.
Steps 11 to 13 describe how the Tim Menu may be
used to calibrate the complete loop and to
compensate for thermocouple errors.
Step 1 Initialisation
When power is applied to the loop the
BA578C will automatically perform the
initialisation routine described in section
2, and then display and transmit the
thermocouple temperature using the
existing calibration information.
Step 2 Enter the programme menu
Enter the programme menu by
simultaneously pressing the
P and E
buttons. The transmitter will respond by
displaying 'COde'. Press
P to clear this
prompt and set the display to the
security code 1209 using the
Up , Down
and P push-buttons. Pressing E will
enter the code. After a few seconds
during which all the decimal points will
be activated, the first parameter 'InPut'
will be displayed.
Step 3 Define input
With 'InPut' displayed press P which
will reveal the current transmitter sensor
type. Using the
Up or Down button
scroll through the menu until
thermocouple input 'tHC' is displayed.
Step 4 Define type of thermocouple
With 'tHC' displayed press P to enter
the thermocouple sub-menu. The first
parameter 'tYPE' will be displayed,
pressing
P again will give access to the
seven different types of thermocouple.
Select 'J' using the
Up or Down button
and then press E to return to the
sub-menu.
Step 5 Define units of display
Using the Up or Down button select
'dEg', from the sub-menu and press P
to reveal the current units. Pressing the
Up or Down button will toggle between
o
C and
o
F. Select
o
C and press E to
return to the sub-menu.
Step 6 Resolution
Using the Up or Down button select
'rESn' from the sub-menu and press P .
Pressing the Up or Down button will
toggle between high and low resolution,
select 'Hi' and press
E to return to the
sub-menu.
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