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8.3.5
Connection of external DSfG-Device-F via Modbus
The intension to connect Ultrasonic gas meters comparable to an electronic evalu-
ations unit via the same protocol arises due to the wish to transfer "all" data deter-
mined by an ultrasonic gas meter, i. e. measured values as well as status infor-
mation or diagnostic data. Therefore, the connection via DSfG-device-F has be-
come the standard in Germany.
Since the USM GT400 does not have its own DSfG bus access, its DSfG-in-
stance-F protocol is implemented externally via a flow computer, the ERZ 2000-
NG, which has this access. To realize the access the necessary data are trans-
ferred between the ERZ 2000-NG and USM GT400 via Modbus, which is often
referred to as Instance-F, although it only provides the data required for DSfG
Instance-F.
1
ERZ 2000NG with external DSfG device F
2
USM-GT-400 Ultrasonic flow rate meter for gas
Fig. 8.17: Data exchange between ERZ 2000 NG and USM-GT-400
The corresponding settings can be found in the VK Modbus Master USM menu in
the ERZ2000-NG. The corresponding register expressions can be found in the VJ
register expressions menu. In the USM GT400, the Modbus registers of instance F
are listed in column BA.
8 Installation
Manual USM GT400 · EN10 · May 2021
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