- 10 -
(1) P (proportional action)
Control output rate (%) is set for measuring range.
Control output value changes in proportion with measured
value (PV) and set value (SV).
For wide proportional band, change of control output is small
relative to deviation. The narrower the proportional band is,
the larger the output variation is and the more intense
proportional action is. Too narrow proportional band causes
ON-OFF like action with oscillation.
(2) I (integral time)
A function that compensates the offset created by
proportional action. Effect of compensation is weaker for
longer integral time and is intensified by shortening time.
Too short integral time causes integrating hunting and may
result in wavy operation.
(3) D (derivative time)
Improves stability of control by reducing overshooting of
integration from expected change of the control output.
Effect of compensation is weaker for shorter derivative time
and is intensified for longer time. Too long derivative time
may result in oscillating operation.
6-3. Control output characteristics (
digit of function
selecting screen of mode 2 screen group)
Control output characteristics determines the control output
direction according to the measured value (PV) relative to the set
value (SV).
(1)
(RA characteristics)
Control output increases for lower measured value relative to
set value, it is used for heating on temperature control.
(2)
(DA characteristics)
Control output decreases for lower measured value relative to
set value, it is used for cooling on temperature control.
6-4. Error message
(1) Defect of measuring input
In case of thermocouple break, R.T.D. A break
and PV being approx. 10% greater than higher
limit of measuring range.
In case of PV being approx. 10% less than the
lower limit of measuring range with inverted
polarity of input wiring.
Cold junction (CJ) defect to higher side for
thermocouple input.
Cold junction (CJ) defect to lower side for
thermocouple input.
Break of B or B and multiple break of A, B, B
upon R.T.D. input
(2) Defect of Heater Break Alarm CT Input
The CT input value exceeds 55A (550A for 0~5V
DC input).
The CT input value falls to -5A (-50A for 0~5V
DC input) or lower.
7. Instructions on Communication
7-1. General
Section 7 deals with communication interface, which is an
optional function, and communication procedure.
For the SR73A and 74A series, two types of communication
interface, RS-422A and RS-485 are available. Each enables a
personal computer or the like to set and read various data by the
use of signals which conform with EIA standards.
RS-422A and RS-485 are communication standards established
by the Electric Industries Association (EIA), which are meant for
electrical or mechanical matters, the so-called hardware, but not
for the software portion of the data transmission procedure.
Accordingly, communication even with an apparatus having the
same interface cannot be made unconditionally. It requires a
thorough understanding of specifications and procedures.
The use of RS-422A or RS-485 allows a plurality of apparatuses
to be connected in a parallel configuration. It is also possible to
use a line converter for conversion of RS-232C to/from RS-422A
and RS-232C to/from RS-485.
7-2. How to connect SR73A or 74A with host computer
7-2-1. Control signals
Since the apparatus is provided with input/output transmitting and
receiving data lines and an earthing line for signals but not with
any other signal line, control signals should be processed by the
host side.
The method of processing differs from system to system and
connection details should meet requirements of the host
computer. Examples of connection are shown in the following.
7-2-2. Connection of RS-422A
(1) The logical levels of input and output of this apparatus are
basically as follows:
Mark state
**– <**+ (Example: SD- < SD+)
(including the state in which communication is not carried
out)
Space state
**– >**+ (Example: SD- > SD+)
However, since the impedance of SD+ and SD- of this
apparatus is high until just before transmission, the above
levels are output just before commencing transmission.
(2) Example of Connection of RS-422A
Note:
Message of heater break alarm is only displayed on
heater break alarm set screen.
is shown when output is OFF. It is not
defective.
Note:
Contact to us or our representative in case of any defect
regarding this product.
SD
SD
RD
RD
SG
+
-
+
-
+
-
+
-
+
-
+
-
SD
SD
RD
RD
SG
2
3
4
5
1
terminal No.
SD
SD
RD
RD
SG
2
3
4
5
1
Host computer
Shielding wire
Transmitted data
Received data
Earthing for signal
Transmitted data
Received data
Earthing for signal
FG (Earthing for protection)
Terminal resistance (510
Ω
)
SR73A and 74A Controllers 1
terminal No.
SR73A and 74A Controllers 2
Note:
Some line converters between RS-232C and RS-422A
may have the following indication for terminal
(connector) output. If that is the case, logical levels
should be checked before connection.
