All of the VPFlowScopes have 1x analog output. This can be used as (only 1 at the time):
Using the analog output the sensors can be read out remotely, for instance by a DCS control or central supervision system (like VPVision). In this chapter we will explain:
- Usage of 4..20mA output.
- How to change the settings.
The explanation of the alarm function (VPFlowScope M only) will be covered in chapter C8 Alarm Settings.
2. The 4..20 mA output
The analog output is default set to 0 to 100% of the flow range in mn/sec. Measurand, unit and the range can be adapted without influencing the measurement itself. The 4 .. 20 mA output is an active, non- islolated linearized current loop that can be used to connect the VPFlowScope to a control system.
The 4..20mA can give output in flow, pressure or temperature. All options are:
|Flow / Velocity||mn/sec|
|For volumetric flow: do not forget to program the pipe diameter first in your flow meter. This is already done for the VPFlowScope In-line.|
4 mA (zero) = lowest end of the range.
20 mA (span) = highest end of the range.
Choose any range you like. The smaller the range, the higher the resolution over the 4..20 mA scale. The analog scale will not affect your original measurement range.
The flow meter sensor measures bi-directional flow. You can set the analog output to your liking either single-direction or bi-directional.
2.2 Single direction
So when output is: 12 mA. –> the measurement corresponds with 75 mn/sec.
The 4..20mA output corresponds to a bi-directional functionality of the set range from negative flow to positive flow.
Example 1: Complete bi-directional
- 4 mA = -150 mn/sec
- 20 mA = + 150 mn/sec
So when output is: 12 mA –> the measurement corresponds with 0 mn/sec.
Example 2: Partial bi-directional
Application: Keep your resolution as much as possible for the positive flow direction, and you only want to detect if there is a negative flow without knowing how much.
- 4 mA = -1 mn/sec
- 20 mA = + 80 mn/sec
So when output is: 12 mA –> the measurement corresponds with 39.5 mn/sec.
2.4 Fault condition feedback
The output will drop (close) to 0mA in case of a fault condition. Possible fault conditions are:
|VPSensorCartridge / sensor is disconnected.|
|The power is below the minimum level (11.6 VDC).|
|VPSensorCartridge gives an error code.|
The VPFlowScopes feature a low-frequency active pulse output.
- The pulse is a ‘non-potential’ free output – as it acts as a controlled current loop.
- It can be made passive: using an external isolator.
The pulse will be generated via the 4..20 mA when the interval exceeds the selected value.
Default pulse settings for different diameters:
|> 40mm and < 92mm||> 1.57 inch and < 3.62 inch||1 m3n|
|> 92mm and < 160mm||> 3.62 inch and < 6.3 inch||2 m3n|
|> 160mm and < 205mm||> 6.3 inch and < 8.07 inch||5 m3n|
For the VPFlowScope In-line, the default value is different by the set diameter of the sensor.
|< 25 mm||< 0.5 inch||0.1 m3n|
|> 25 and < 45 mm||> 0.5 and < 1 inch||0.2 m3n|
|> 45 mm||> 1 inch||1 m3n|
You can set the amount of flow per pulse, with a maximum pulse frequency: once per 2 sec.
If the pulse interval is set small, a continuous pulse (20mA high level) will be the result.
3.1 Pulse and Totalizer
The pulse output is connected to the internal totalizer value.
When the totalizer has increased by the programmed pulse interval, the pulse will be generated.
A negative pulse cannot be generated. In the case of negative flow:
- The internal totalizer will count backward.
- Pulses will not be generated until the same amount of positive flow has been added to the totalizer again.
The options can be found at: Menu >> Settings >> Connectivity >> Analog.
Use the up and down keys to navigate through all options. Use Enter to save the settings.
First choose usage, by adapting: Mode. Choose between:
- 4..20 mA
When the following mode is selected: Alarm. See chapter C9 for further explanation.The next step is setting up the settings.
- When the following mode is selected: Pulse.
Go to: Menu >> Settings >> Connectivity >> Pulse.
Select the desired unit
- When selected 4..20mA. :
Go to: Menu >> Settings >> Connectivity >> 4..20mA.
Select the desired unit, it is only possible to select one unit at the time.
In VPStudio unfold the settings menu of the flow meter and select “Settings”.
Go to the tab “Analog output”. Select the right I/O mode: 4..20 mA, pulse or alarm (alarm option is for the VPFlowScope M only)
For each selection, the dedicated settings will become visible. See 5.1 to 5.3.
5.1 The 4..20 mA output
- First, select the right unit.
- Is this a volumetric unit: Make sure the pipe diameter is programmed. (See chapter C3). This will be calculated in the settings.
- Set the 4 mA and 20 mA values accordingly.
- Click “Save”.
- Select the pulse unit and the desired pulse interval.
- Click “Save”.
The alarm settings and applications will be explained in-depth in chapter C8 Alarm Settings.
For adjusting the analog settings via Modbus, please see chapter G8.
7. Next Step
Learn more about the next communication protocol: C7. Ethernet Settings.
For more information about the data logger go to: C9. Data logger settings.
Or directly go to the next step in installing your flow meter.
|Using analog communications will also provide you with the option to set an alarm. The alarm settings can be found in chapter C8 Alarm Settings.|
|Go straight-away to the mechanical installation: D1. Select the right installation point.|