User manual for RTD,TC,mV/4-20mA converter module SPT-86L
5.
PRINCIPLE OF OPERATION
SPT-86L
module allows the conversion of temperature and voltage on current in 4-20 mA
standard. Present value of temperature or voltage is available as measurement register of
device (reg. addr. 01h). I
f input signal exceeds the permissible range, shortcut or break of
measurement circuit occur, appropriate error code will be set in
status register
(register 02h).
Measurement input's parameters are located in the group of registers
”
Input
” (see
LIST
OF REGISTERS
on page
18
) and allow:
•
input type selection (parameter
”
InputType
”)
•
connection type selection (parameter ”
InputConn
”, applies only to RTD measurement),
•
change of the filtration degree of the values in measurement register (parameter
”
InputFilter
”),
•
shift of the measurement scale (parameter ”
InputOffset
”, applies only to temperature
measurement),
•
processing characteristic setup (applies only to voltage measurement).
The proper operation of the module is signalized by flashing green LED diode placed on
the front panel and labelled
RUN
. The yellow LED diode (labelled
RS-485
), by fast flashes,
signalizes data transmission via serial interface. The red LED diode (labelled
ERROR
), if lit,
signalizes measurement error. It may mean that measured signal exceeded the permissible
range, the sensor was damaged or wires' short circuit or break occurred.
Parameters are kept in non-volatile EEPROM memory. All parameters can be set via
serial interface (see
LIST OF REGISTERS
on page 18
).
5.1.
VOLTAGE MEASUREMENT
Measurement results can be internally recalculated due to one of available
characteristics: linear, square, square root or user definable multipoint (max. 20 points length).
The expansion of nominal range is defined by
”
InputHiRange
”
parameter (see figure below).
Fig. 5.1
Example of definition of permissible range of input signal -
”
InputHiRange
”
parameter (0-100 mV mode)
8
”
InputHiRange
” = 5,0 % (5 mV)
105
permissible measurement range
nominal measurement range (0-100 mV)
[mV]
100
120
0
U
max
range exceeded
range exceeded
