BEKA BA374C, Руководство пользователя

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8. CALIBRATION EXAMPLE
In this example a BA374C 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
Trim 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
BA374C 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.
Step 7 Cold junction compensation
In this example only one thermocouple
is connected so cold junction
compensation is required. Using the
Up or Down button select 'CJC' from
the sub-menu and press P . The Up
and Down buttons will turn the cold
junction 'On' and 'OFF'. Select 'On' and
press
E to return to the sub-menu.
Step 8 Input open circuit drive
Using the Up or Down button select
'burn' from the sub-menu and press P
to reveal the current status. Select 'uP'
using the
Up or Down button and press
E three times to return to the 'InPut'
prompt via the 'burn' and 'tHC' prompts.
Step 9 Calibrating the 4/20mA output
'CAL' defines the display at which the
output current is 4mA and 20mA.
Select 'CAL' from the menu using the
Up or Down push-button, and enter the
sub-menu by pushing P . The
transmitter will display a 'ZEro' prompt
requesting the display at which the
output is to be 4mA. Press
P and
enter -10.0 using the Up , Down and P
buttons. Press E to return to the 'ZEro'
prompt. Select 'SPAn' from the
sub-menu and press
P . Enter 240.0
which is the display at which the output
current is to be 20mA and press E twice
to return to the 'CAL' prompt.
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