Appendix A - Modbus - Sentry Sample II Low Pressure Installation, Operation & Maintenance Manual

Appendix A - MODBUS

Multiple Sample Sentry II controllers can communicate with a PC or control system via
MODBUS over a half duplex (2-wire), RS-485 network.
Figure 28 shows the MODBUS setup screen on the Sample Sentry II.
Figure 28. MODBUS Setup
Each device on the network must be assigned a unique address. The address for each
Sample Sentry II can be in the range of 1 to 247. Use the ▲ and ▼ keys to change the
address setting. Use the ENTER key to toggle between the address setting and the BAUD
setting.
The controller is capable of operating using a BAUD rate of 19.2 kbps or 9600 bps. To
change the BAUD rate use the ▲ and ▼ keys.
The communications port uses 8 data bits, 1 stop bit, and no parity. The MODBUS mode is
RTU. These parameters cannot be changed.
Table 6. MODBUS Registers
Register
30001
30002
30003
30004
30005
30006
30007
30008
30009
30010
30011
30012 / 40012
30013 / 40013
30014 / 40014
30015 / 40015
30016 / 40016
Sentry Sample Sentry II
M O D B U S
►
A d d r e s s
B A U D
Sample Sentry II Register
State
Flow rate
Inlet Pressure
Outlet Pressure
Inlet Temperature
Outlet Temperature
Cooling Out Temperature
Sample Shutoff Valve (V1)
Analyzer Valve (SV2)
PRV Valve (# turns open)
Elapsed Blowdown (seconds)
Sample Flow rate Set-point
Blowdown Flow-rate Set-point
Blowdown Duration Set-point (seconds)
Startup Pressure
Remote Start
S e t u p
1
9 6 0 0 b p s
R/W
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read Only
Read / Write
Read / Write
Read / Write
Read / Write
Read / Write
Format
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
INT 16
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