Siemens SITRANS FUH1010, Инструкция по эксплуатации товара, Страница: 99 / 264

Functions
7.3 Span Data
FUH1010 IP65 NEMA 4X Precision Volume
98
Operating Instructions, 01/2013, A5E32122003-AA
Adjusting the PGEN Output
The default setting for the Digital PGEN output provides a 5000 Hz frequency at an assumed
maximum velocity of 100 ft/sec. In certain cases it may be necessary to change this default
PGEN value. For example:
●
If the PGEN signal cable is very long, then the added cable capacitance may prevent
reliable RTU pulse detection at or near 5000 Hz. In this case it may be necessary to
decrease the PGEN (Pulses / Unit Volume) setting using the equation below.
Pulses / Unit Volume = MaxFreq / MaxFlow
Where:
MaxFreq = Maximum desired frequency (Hz)
MaxFlow = Maximum flow rate (Unit Volume / second)
For very low operating flow rates, the pulse frequency may approach the 20 Hz limit of the
PGEN output. In this case it may be necessary to increase the PGEN (Pulses / Unit Volume)
setting.
Pulses / Unit Volume = MinFreq / MinFlow
Where:
MinFreq = Minimum desired frequency (Hz). Must be greater than 20 Hz!
MinFlow = Minimum operating flow rate (Unit Volume / second)
Note
If STD VOL is selected then the "unit volume" for PGEN will represent Standard Volume, not
actual volume.
Forcing the PGEN Output Frequency
To test the operation of the flow meter with a Remote Transmitting Unit (RTU), or other pulse
counting device, it may be necessary to force the PGEN output frequency, especially when
the pipeline is not flowing during flow meter commissioning. This can be accomplished by
setting the AnCal diagnostic value to a flow rate corresponding to the desired frequency
output. (Refer to the appropriate paragraph in your manual for operation of the AnCal
function.)
The example below demonstrates how to calculate the AnCal flow rate based on the desired
pulse output frequency and the entered PGEN (Pulses / Unit volume) setting:
For PGEN setting = 53 Pulses /CU FT and a desired frequency = 1000 Hz
1.
Temporarily change flow rate units to CU FT / SEC (Use same volume units as Totalizer.)
2. Set AnCal = 1000 / 53 = 18.868 CU FT / SEC
3. 1000 Hz frequency should now be observed on the PGEN output.