5
CONV 4/420/A - CONV 8/420/A
TECSYSTEM S.r.l ®
6) LUMINOUS INDICATORS
Lighting of ON led near the supply connector detects 24 Volts voltage supply.
RS led must be off with correct working conditions.
It turns on and stay fix in case the serial line should be cut out or in case of wrong con-
nection.
If it blinks, it means that the serial transmission is disturbed by strong external interfer-
ences; therefore it is necessary to verify that you are using a shielded cable, that it is one-
sided grounded and that it is placed the farthest possible from power lines or interference
sources.
5) 4.20 mA OUTPUT CONNECTION.
CONV 4/420/A module has 4 4.20 mA outputs whilst CONV 8/420/A module has 8 out-
puts.
To each 4.20 mA output it is possible to connect a read-out or acquisition device.
Admitted load impedance for each output goes
from 0 to 500 ohm
.
4-20 mA signal is referred to 0-240°C range with an accuracy of 1% compared to full
scale value.
It is possible to ask for a special calibration referred to a 0-200°C range.
For 0-240 range current temperature relation is the following:
I
out
= (T/15)+4
(T= temperature in °C)
Example:
If T=100°C
I
out
= 100/15+4= 10,67 mA (±0.2 mA)
For 0-200 range, relation is: I
out
= (T/12,5)+4
(T= temperature in °C)
For -40 +200 range, the relation is: I
out
= (T/15)+1/015
(T= temperature in °C)
7) WORKING NOTES
To work, the module doesn’t need any programming since it gets all the necessary infor-
mation from NT935 / NT538 temperature control monitoring device.
4.20mA outputs are active-type; therefore they don’t need any additional supply.
Serial communication between temperature control monitoring device and 4.20 mA mod-
ule is active only when NT935 or NT538 are in temperature control working mode in one
of foreseen modes (Scan, Auto, Man e T.Max).
When other functions, such as programming, programming display and test relays are
activated, serial communication with the add-on module is temporarily disabled.
