VP instruments VPFlowScope M probe, User Manual, Page: 23 / 48

Connectivity 23
© 2016 Van Putten Instruments BV | MAN-VP-SMPR-UK | Revision:1600 | Date:23-03-2016
For scaling purposes, the zero and span matching 4 and 20mA can be modified. This will not affect
the original measurement range. The 4 mA is representing the lowest end of the range and 20 mA
the highest. The range can be adjusted to increase or narrow the resolution. For bi-directional
measurement, the zero value needs to be set to a negative number which will result in 12mA for zero
flow.
Configuration with VPStudio 2.0
VPStudio 2.0 has graphical visualization for the 4..20mA settings. The actual settings will be shown
next to the factory settings.
With VPStudio 2.0, in the pull down menu, you can choose above units to assign to the output.
Adjust the zero and span for scaling.
Changing to volumetric units, the programmed diameter is calculated in the settings. So change the
diameter first, then the analogue settings. VPStudio 2.0 provides feedback while you are changing
the settings. Use “set default” to go back to the factory default.
4..20mA output
Single direction Bi directional
0% | 100% flow: 4 ma = 0 -100% | 100% flow: 12 ma = 0
7.3 Pulse output
The VPFlowScope M probe features a low-frequency active pulse output. The pulse is a ‘non
potential’ free output as it acts like a controlled current output. To make it passive, an external
isolator can be used.
The pulse interval can be set with the VPStudio 2.0 software. This enables you to choose the amount
of flow per pulse. A pulse from 0..20 mA will be generated when the interval exceeds. The maximum
pulse frequency is once per 2 seconds. If the pulse interval is set to small, a continuous pulse (20mA
high level) will be the result.
The pulse output is connected to the internal totalizer value. When the totalizer has increased by the
pulse interval, the pulse will be generated. As it is not possible to generate a negative pulse, negative
flow can not be indicated by pulse. In case of negative flow, the internal totalizer will count
backwards. Pulses will not be generated until the same amount of positive flow has been added to
the totalizer again. In this way we ensure that the pulse output will always be synchronized with the
internal totalizer of the VPFlowScope M probe. In case of continuous negative flow, consider to swap
the flow meter direction.