Endress+Hauser Tankvision Gauge Link NXA20, Руководство по эксплуатации

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Operation Tankvision Gauge Link
34 Hauser
up from the gauges, it is important that the Modbus host has been configured to calculate
the different units. The Tankvision Gauge Link can support gauges on the same field bus
with different units, but in practice, all the gauges on the field bus would typically have the
same units.
The scan cycle is the level is polled on a frequent basis, temperature is polled for
approximately half to a quarter the level depending on the gauge type. Other parameters are
polled once every cycle. The cycle time is dependent on the number of gauges and
parameters configured.
If a gauge was lost the Tankvision Gauge Link would do a number of polls for that gauge, if
still no gauge was detected, it would set all the registers associated with that gauge to
0xFFFF hex. It would then move on and poll for the rest of the gauges. Depending on the
gauge setup, if an auxiliary device was connected such as a DAU and comms was lost to the
gauge but not DAU, the data from the DAU would still be returned, this would also apply if
comms was lost from the DAU but not the gauge.
If a parameter from the gauge had an error, the last valid reading would be returned to the
Modbus map, but the status bit(s) would be set to indicate an error, the last valid reading can
be useful to know when troubleshooting.
Commands can be issued from the Tankvision Gauge Link, if the gauge supports it, such as
stow, density dip etc.
A range of other data can be read from the gauges as detailed in the Modbus specification
document. These parameters must be setup in the appropriate gauge, such as the high and
low alarms.
The Tankvision Gauge Link has a heartbeat and various information registers, these are
detailed in the Modbus map manual.
Generally the status register offset 21 is used to read the status of the gauge such as ‘is the
gauge doing a water dip?’ etc. The status register for each parameter is generally used to test
whether the parameter is healthy or not.
7.3 Engineering mode
This mode allows, Ensite, Engauge or Winsetup to be connected to the RS232 port and used
to interface directly to the gauges.
When using these tools a trained engineer much be familiar with the tools.
Data, such as level, temp etc, can still be read from the gauges when using the tunnelling
engineering tools, but if the tools are running for long periods of time an update of new date
to the Tankvision Gauge Link may take some time. It is important that the control room must
be made aware that the data from the modbus link may not be live. It is the responsibility of
the engineer to ensure that the data read from the Tankvision Gauge Link may not be live
when using the engineering tools and advise the control room of this.
If the engineering tool stops communicating through the Tankvision Gauge Link for 1
second, then the Tankvision Gauge Link will then start polling for data. As soon as the
engineering tool starts sending data to the gauges, the Tankvision Gauge Link then stops
polling for live data.
The COMMUNICATIONS understood LED will not flash when the engineering tool is passing
data through the Tankvision Gauge Link. This can be useful to determine which device is
polling for data.