11
GF U3000 V2 Ultrasonic Flowmeter
Modbus Supplement to the operating instructions
Regime
Property
Metric1
Imperial
US Imperial
Metric2
Velocity
m/s
ft/s
ft/s
m/s
Volumetric Flow
l/s
gallons/s
US gallons/s
m
3
/hr
Volume
litres
gallons
US gallons
m
3
Energy
KWH
BTU
BTU
KWH
Power
KWH
BTU/sec
BTU/sec
KWH
Acceleration
m/s
2
ft/sec
2
ft/sec
2
m/s
2
All other updateable registers can be set by either the unit, or by the MBM. A simple example are the Totals registers. In normal
operation they are updated and may be read by the MBM, but they may also be used to rest the totals using the procedure outlined
in the ensuing paragraphs.
Updateable unit functionality includes:
•
Updating forward and reverse flow totals,
•
Updating forward and reverse energy totals (reverse energy totals are not yet implemented),
•
Updating the lock screen mode,
•
Updating the damping mode and time, and
•
Updating the dynamic damping acceleration threshold.
Changes to these registers need to be specifically allowed by the unit. Changes to totals may be disallowed by setting the “Block
remote total changes” setting to Yes in the Modbus settings menu. Blocking all updates by the MBM is accomplished by setting “Block
all remote changes” to “Yes”. The status of these settings is reflected in register 8 (offset 7) bit 2 and register 7 (offset 6) bit 1 res-
pectively (see the Map).
3.5
General Procedure for Updating Unit Settings
Other than the Modbus measurement regime, all registers that result in settings or values in the local unit being updated, have flags
associated with them. Values can be written into these registers, but no action will be taken until the associated flag is activated.
There are three key flags that must be considered when updating these registers.
The first and most important is the Lock-out Updates (bit 0) in the Instrument Control flags register number 6 (address 5). This bit
ensures that registers will not be updated by the device until the flag is reset. The purpose is to ensure that the values being updated
are not overwritten with updated values from the unit. For example, imagine resetting a total only to have its value overwritten by an
update from the unit before it can be set in the unit. More examples will follow, but in general it is good practice to set this flag befo-
re writing and reset it after the operation is complete. It is important to remember that values will not be updated until this bit is
reset.
The other two bits that are important are the Remote Total Changes Disabled flag (bit 2) of the Instrument Status flags register 8
(address 7), and the Remote Lockout flag (bit 1) of the Instrument General Flags register 7 (address 6). Together these are referred
to as the inhibit bits.
The Inhibit flags are controlled by the local unit. If the “Remote Total Changes Disabled” flag is set, it blocks the ability of the MBM to
update or reset the totalling registers. If the “Remote Lockout” flag is set, it blocks the ability to write and update any registers that
may change the unit’s settings. This includes all writeable registers. This allows a field technician to stop the unit’s settings being
changed remotely while maintenance or fault finding is being undertaken. This setting should be reset once the task is complete.
