Output Function - Omega FMG600 Series User Manual

Design, Assembly and Service Manual
Page 29 of 44
Induction flow meter FMG600 series
Equipment with voltage input Current output connected as a voltage
source to feed the (passive) output 2
The output voltage for the associated equipment is defined as the voltage drop on resistor R. It holds:
U = I R.
For the voltage range of 0.. 10V, select R = 500 Ω and the analog current output range 0.. 20mA. Resistor R
shall be placed as close to the input terminals of the co-operating (controlled) equipment as possible. The
maximum voltage (voltage drop on the resistor) is 10V. The input impedance of the controlled equipment
shall be at least 100 times higher than that of resistor R.
The interconnection of the current output as an auxiliary power source for the binary outputs is shown in the
above picture. This arrangement assumes that the current output is not used for the purposes of flow rate
indicator. Here the current output needs be set in the "Fixed current" mode of operation. The voltage drop on
resistor Ri is used as supply voltage for the binary output (via resistor Rz). The input impedance of the
associated equipment shall be at least 10 times higher than that of resistor Rz, while Rz shall be at least
10 times higher than Ri. It holds: Ri < Rz < input impedance of the associated equipment.
Technical specifications of analog output
The analog output is controlled by a 12-bit DA converter. The operational range 0 to 20mA is divided into
4,096 steps. One step (1LSB) therefore corresponds to about 0.005mA (0.025% of 20mA). This resolution
applies to all output ranges. The current range 4 ... 20mA is software-defined with the converter steps
reduced accordingly. The maximum voltage at the current output is 20V; the maximum resistance of the
current loop is 1,000Ω.

7.1.4. Output function

The configuration of the induction flow meter includes two binary multifunctional outputs, electrically isolated
by means of optocouplers. The output transistors of the optocouplers are accessible via terminals 12-13 and
14-15. These are passive outputs that need external power source. Alternatively they can be powered by the
analog output in the fixed-current mode as described above. The binary outputs can be loaded and
repeatedly switch on and off currents 1 to 50mA.
Default settings: Output 1: frequency output, Output 2: pulse output.
Flow meter can be equipped with an output relay, designated in the menu as item "Relay functions".
Electrically isolated relay contacts are accessible via terminals 1-2-3. For impulse output, both the impulse
width and the minimum gap length are set at 0,5 s. To ensure correct functioning of the impulse function, it is
necessary to set the outputimpulse constant (the fluid volume per impulse) so that the memory block of
unsentimpulses would never overflow.