VPInstruments VPFlowScope In-line 3/8", User Manual

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© 2021 VPInstruments | MAN-VP-VP38-EN | Revision: 2100 | Date: 25-01-2021
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8 Modbus
Introduction to Modbus
A complete introduction on the Modbus standard can be found on www.modbus.org. See the
document Modbus_over_serial_line_V1_02.pdf, which can be downloaded from their website. We
strongly recommend to download and read this information carefully before installing Modbus
communication. The following paragraphs in this chapter assume you are familiar with the Modbus
communication standard.
All measurement parameters are available through Modbus in floating point and integer format. The
data will be refreshed every second. Maximum polling interval is 10ms.
The Modbus settings can be changed in the menu using the key pad. Below shows all available
options
Hardware address: 1-247
Integer multiplier: 1-1000
The default settings are hardware address 9 and integer multiplier 10
Data format
Function code 0x03 for reading(Holding register)
Function code 0x06 for writing single register(Holding register)
Function code 0x10 for writing multiple registers(Holding register)
Data format is little-endian word order, big-endian byte order within the word. [CDAB]
Register map
The actual measurement data is placed in holding registers. To read out data, you will need to use
the corresponding holding registers.
Counting starts from 0: register 0 is register index 0 (first) and register 1 is register index 1 (second)
This table starts with register 1 because register 0 is unused.
HEX Decimal Description Type Read / Write
General information
0001 - 0002 1 - 2 Serial number 32-bit integer Read
0003 - 0005 3 - 5 Firmware version: major, minor,
patch 3 words Read
0006 - 0007 6 - 7 Production date 32-bit integer ** Read
Flow
0064 - 0065 100 - 101 Flow range min m
n
/sec Floating point Read
0066 - 0067 102 - 103 Flow range max m
n
/sec Floating point Read
0068 - 0069 104 - 105 Flow m
n
/sec Floating point Read
006A - 006B 106 - 107 Flow sfps Floating point Read
006C - 006D 108 - 109
Flow m
3
n
/hr
Floating point Read
006E - 006F 110 - 111
Flow m
3
n
/min
Floating point Read
0070 - 0071 112 - 113
Flow m
3
n
/sec
Floating point Read
0072 - 0073 114 - 115 Flow l
n
/min Floating point Read
0074 - 0075 116 - 117 Flow l
n
/sec Floating point Read
0076 - 0077 118 - 119 Flow SCFM Floating point Read