Siemens 7ML19985AB01 Flow Velocity Input, Auxiliary Head Input, Voltage Input Current Input

FLOW VELOCITY INPUT

In some applications, the flow calculation for the chosen primary element requires a velocity input. In this type of application, the transducer measurement is used to calculate the cross sectional area of the flow. By multiplying the area with the distance per time units of velocity, the volume per time units of flow are calculated. The calculated velocity can be viewed via D8.

The 0% and 100% limits of the velocity input must be scaled using parameters P8 and P9.

»select P8

»enter the voltage corresponding to zero velocity

»select P9

»enter the velocity corresponding to 5 V

e.g.	If the velocity sensor output is 1 V per m/sec and the output is
	scaled for 7 V at 100% velocity (7 m/sec), then enter 5 m/sec. If the
	output is scaled for 4 V at 100% velocity (4 m/sec), enter 5 m/sec.

P8 and P9 can only be accessed if P3 has been set for an option that requires the use of a velocity input. The input voltage level can be viewed via D12.

Voltage Input Current Input

typical 1 - 5 V signal from	typical 4 - 20 mA signal from velocity sensor.
velocity sensor.	Add terminating resistor.
	e.g. 250 Ω for 1 - 5 V over 4 - 20 mA.

Signal must be positive with respect to ground.

Velocity Input (additional to Basic Wiring)

AUXILIARY HEAD INPUT

In some applications, the transducer input (TB1-1/2) is not used to provide a signal for head measurement. A typical example of this is an application which is beyond the 3 m (10 ft) range of the OCM-3. In such a case, the head could be derived from another Milltronics level monitor or other compatible device.

The method of head determination is set by P42. The OCM-3 simply substitutes the signal from the auxiliary device for the ultrasonic measurement provided by the transducer. The programming and consequent flow calculation are performed

as normal.

7ML19985AB01 OCM III 36