User manual - METER SUR-457
Calculated I
out
do not exceeds the output working range (3.8 - 21 mA).
b) D = „20.5”
According to formula from page 35:
I
out
= (20.5-10.0) / (20.0-10.0) × 16 mA + 4 mA = 1.05 ·16 + 4 = 20.08 mA
Calculated I
out
do not exceeds the output working range (3.8 - 21 mA).
c) D = „30.0”
According to formula from page 35:
I
out
= (30.0-10.0) / (20.0-10.0) × 16 mA + 4 mA = 2 ·16 + 4 = 36 mA.
Calculated I
out
exceeds the output working range (3 - 21 mA), so current output will generate
current equal to the upper border of range defined by parameter
“Lo r”
and
“Hi r”
(it means
21 mA).
10.
THE MODBUS PRO
TOCOL HANDLING
Transmission parameters: 1 start bit, 8 data bits, 1 or 2 stop bit (2 bits are send, 1 and 2 bits
are accepted when receive), no parity control
Baud rate:
selectable from: 1200 to 115200 bits/second
Transmission protocol:
MODBUS RTU compatible
The device parameters and display value are available via RS-485 interface, as HOLDING-
type registers (numeric values are given in U2 code) of Modbus RTU protocol. The registers
(or groups of the registers) can be read by 03h function, and wrote by 06h (single registers) or
10h (group of the registers) accordingly to Modbus RTU specification. Maximum group size for
03h and 10h functions can not exceeds 16 registers (for single frame).
The device interprets the broadcast messages, but then do not sends the answers.
10.1.
LIST OF REGISTERS
Register
Write
Range
Register description
01h
No
-999 ÷ 9999 Measurement value (no decimal point)
02h
No
0h, A0h, 60h,
C0h, 10h,
20h
The status of the measurement;
0h
- data valid;
A0h
- top border of
the measurement range is exceeded;
60h
- bottom border of the
measurement range is exceeded;
C0h
- sensor failure;
10h
- error
of user characteristic;
20h
- waiting for the first measure
03h
Yes
0 ÷ 3
“
Pnt
” parameter in “
InPt
” menu (decimal point position)
0
- “
0
”;
1
- “
0.0
”;
2
- “
0.00
”;
3
- “
0.000
”
04h
Yes
see descr.
State of the relays (binary format)
(1 - on, 0 - off):
00000000 0000dcba
a
- relay R1;
b
- relay R2;
c
- relay R3;
d
- relay R2;
If written, only
a
,
b
,
c
,
d
bits are important (others are ignored)
these bits allows user to control the relays via RS-485 interface
05h
1
Yes
0h ÷ 1800h State of active current output, expressed in 1/256 mA units – it
means that high byte express integer part, and low byte fractional
part of desired output current.
49
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