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Frequently asked questions

What is the capacity of the VPFlowScope data logger?

The VPFlowScope has a great feature: the data logging display! It contains 2 million points that can be assigned to three channels. You can change the measurement interval for the flow, pressure and temperature channel.

Example: when you use flow, pressure and temperature all at 1 second interval, each channel generates 86,400 points per day. This will result in a full memory in about eight days with the 2 M points memory).  See the user manual for further details. The old type displays have 500,000 points.

To save memory capacity for flow, pressure and temperature, the real totalizer values are not stored in the data logger memory. We only store the initial totalizer value. VPStudio calculates the totalizer values using actual flow and the time interval. This can lead to differences between the actual totalizer as seen on the display and the  calculated totalizer from data log sessions. In any case, you can always check the display directly after the air audit, to get the actual totalizer value.

Can I use the VPFlowMate / VPFlowScope for vacuum flow?

Yes, you can. But be careful: the VPFlowScope pressure sensor indicates gauge pressure. So it does not show any reading below atmospheric pressure. Please consult factory in that case. The thermabridge sensors have been used down to 300 mbar absolute and do not show significant additional errors at these vacuum levels. So you can use them to measure the “consumption” of packaging machines, vacuum suction cups and centralized vacuum systems.

Are readings normalized to standard pressure and temperature?

Yes! The VPFlowMate and VPFlowScope are mass flow based products. So they relate every measurement back to reference conditions.
We chose for 0° C and 1013,25 mbar as these are global standards. You can convert this to FAD or to other reference conditions yourself.

Additional pressure and temperature compensation is not needed! This saves you money and the data can be easily related to compressor specifications.

Which materials get in contact with compressed air?

The wetted materials for all our thermal flow sensors are:

  • Stainless steel (316 and 304)
  • Anodized auminium
  • Glass
  • Epoxy
What air quality does your flow meter need?

The ISO 8573.1 air quality standard classes is the most suitable compressed air. It ensures that your factory will get the compressed air quality you specified. It can also be used to define the required air quality for sensors used in the compressed air network.

Solids

The best air quality for solids is up to class 5. The after cooler and pre-filter of the compressor have taken out most harmful particles. An additional source of particles can be rust in the pipework. Using a general purpose 1 micron filter will take out any harmful parcicle

Water

The best air quality for water is up to class 6 (non condensing). We have not seen any significant effect on our flow meters. (for more information on water, read on below).

Oil

For short audits, oil does not give any problems, however, a thin film may occur over time. We do recommend a regular check in permanent installations after six months. Once you determine that it is still clean, you can postpone a following check till after one year.

Humidity Effects

Thanks to its high operating temperature, the flow sensor will keep the surrounding air very dry. This minimizes the effect of normal humidity variations.

Variations in Dew Point

In our in-house test facility, we have researched the effects of dew point variations between -20 and +15° C (Class 3 … Class 6 according tot DIN 8573-1).  Our thermabrigde sensor does not show any significant change in sensitivity over this range, which covers most industrial compressed air applications where at least a refrigerant drier is installed.

Condensation effects (droplets)

Once condensation occurs, the gas temperature is close to the dew point temperature.
Example: The air coming from an air compressor has a dew point of 35° C. The outlet temperature is around 50° C. As soon as the temperature drops below 35° C, the water vapor will condensate and form small droplets. Note that the thermal conductivity of water is about 25 times higher than air. Every time a water droplet hits the sensor, the amount of heat conducted to the medium will dramatically increase. Depending on the size of the droplet, the water will evaporate or it will temporarily cover the sensor. In most cases, large spikes can be seen in the output signal. In general, high readings up to 50% have been observed with thermal mass flow sensors.

Solutions :

1 Place the flow meter downstream of a refrigerant/ desiccant drier, or at least at a point where most of the water is separated from the air, for instance behind a receiver tank.
2 When wet air is the permanent condition, a VPFlowScope DP is the best choice.  Please make sure that the installation conditions meet the specific requirements of the DP.

What is the measurement range of your compressed air flow meters?

See our VPFlowScope leaflet for an easy to use range table.

This table applies to the VPFlowScope and VPFlowScope DP compressed air flow meters. In this table, you can see the maximum and minimum flow values for specific pipe diameters. When you have a different diameter, use the VPCalculator on-line tool.

What is the difference between full “percentage of full scale” and “percentage of reading” accuracy?

The accuracy of s sensor or to state it better: the measurement uncertainty can be specified in two ways.

If a meter’s accuracy is based on a percentage of its full reading capability, the error is a fixed value. For example; an error of 0.5% of full scale, in a 150 m/sec device is +/- 0.75 m/sec

At 10 m/sec, the error will be 0,75 / 10, which is 7,5%

If the device has an error expressed as a percentage of the actual flow, then a 0.5% error of 10 m/sec is only 0,05 m/sec.

 

Is modbus RTU always included in your flowmeters?

Yes, of course! Modbus RTU is included. All our flow meters are equipped with Modbus RS485 and use the Modbus RTU protocol. The new VPFlowScope M even has Modbus/TCP. So why use old-school 4 … 20 mA when you can have all parameters at once via Modbus?

Further reading on how to connect to a modbus network can be found here.

What do I need to connect a VPInstruments flow meter?

That depends on the application. For auditors, we have a complete start kit, which contains everything you need. For permanent installation in a BMS, we provide power supply modules, junction boxes and cable as separate items. Or you can simply use an M12 cable, and take care of the rest yourself. Contact us if you need help with connecting everything together. We are happy to help you further!

What type of connections are possible with VPVision?

VPVision offers 8 analog inputs & 1 modbus RS485 input,  to connect 1 daisy chain up to 8 sensors hard-wired directly to the VPVision main cabinet. When VPVision is part of an industrial Ethernet network, you can connect additional sensors using our I/O modules. This saves you significantly on installation and wiring costs.  You can choose from the following I/O modules:
• Modbus extension module with power supply
• Modbus to Ethernet converter with power supply, for RS485 based sensors
• Analog to Ethernet module with power supply, for 4 … 20 mA sensors
• Modbus and analogue to Ethernet module with power supply, to combine both 4 .. 20 mA and modbus based sensors

The Ethernet based I/O modules enable you to overcome great distances in the factory without a lot of wiring. The main VPVision unit also offers 4 LAN ports on the PC. Lan 1 is used to configure the system. The Other LAN ports can be used to connect to the company network, to connect a 3G module or to connect a subnet with I/O modules.

What are the benefits of VPVision Energy Monitoring?

VPVision is unique in it’s class. The Web-Based software offers real-time monitoring of all utilities.
You can view your energy consumption live on anywhere, anytime. On PC, Tablet or smartphone

  • SQL Database
  • Flexible and scalable
  • Easy to use interface
  • Limitless in amount of connected sensors
  • Virtual channels
  • Alarms and reports send by email
  • Third party data base connection (SQL)
  • Open for third party sensors
How can I access VPVision?

VPVision energy management software can be accessed in multipe ways: Ethernet, 3/4G, Wi-Fi, VPN. Your energy data is available anytime, anywhere. In Real-time.

Ethernet
Connecting the VPVision system to a client’s Ethernet will enable everyone, provided they connect to the same network, to access VPV by using the fixed IP-address with any laptop, tablet or smartphone.
VPN (Virtual Private Network) connection.
This will enable users to access the VPVision system from anywhere in the world with a username & password. This is also a very fast and easy way to provide remote support.
Via 3/4G module
Connect a 3/4G module to the VPVision will allow you to access the system from anywhere in the world. The difference between this method & VPN connection is that this does not require the VPVision system to be connected to the customers Ethernet. Additional costs will occur due to use of local network.
Via Wi-Fi
Connect a Wi-Fi module to the VPVision system allows you to access the VPVision software wirelessly within close range of the WiFi module. Please note this would also be possible when connected to the Ethernet of the customer and you are connected to the same network with WiFi. Use the exisitng infographic in leaflet!”

How can i integrate VPVision with the exisiting BMS/PLC/SCADA?

VPVision can be integrated with your exisiting system with the optional SQL module, offering you the last hour data to your master system.

How can I download data from VPVision?

With the CSV widget you can extract data in CSV format. The CSV export wizard can be pre-configured, which makes easy, consistent download of data a very easy task.

How can I expand the VPVision energy management system?

VPVision is easy to expand. We can add sensors to your existing or new hardware and the software can also be easily expanded with optional items and additional sensors. We can update the software remotely. You can also use existing sensors with 4 … 20 mA signals. VPVision grows and adpats according to the needs of your company.

Can you use a 35 bar flow meter in a 40 bar system?

From a safety perspective: yes. We tested our products well above 40 bar. however, the pressure sensor in the VPFlowScope cannot measure higher than 500 psi (which is  a little more than 35 bar). Above this, the sensor will start to behave non-linear, and it will eventually clip. For further details, please check the safety guidelines for the VPFlowScope 40 bar version in the user manual.

What is the recommended installation length for a flow meter?

VPInstruments’ flow meters are calibrated on our proprietary pressurized calibration system, which is unique in the world. Pressurized calibration has many advantages. One of the main advantages is that the calibration conditions are nearly identical to the process conditions in the field. This minimized the total measurement uncertainty. To phrase it simply: It is as accurate as you can get, as long as the flow profile is fully developed and symmetric.

 

Distorted flow profiles

The flow profile in the pipe is probably the biggest enemy to your flow meter’s field accuracy. Pipe bends, elbows, diameter changes, valves will distort the flow profile in the pipe. As the flow meter measures only on one point in the pipe, it cannot “see” these distortions. The flow meter calculates with the ideal, symmetric, fully developed profile.

 

Distorted flow profiles can lead to large measurement errors. So what is the trick: keep enough upstream length before the flow meter and downstream length after the meter. In flow meter terms, we use the term “ X times D” to specify this length. And the X depends on the type of upstream/downstream object. It does not depend on the type or brand of insertion flow meter, as long as it is a single point meter. Only so called “flow conditioners” can reduce the required length.

 

Extensive research has been carried out by various labs, and this has lead to a “generic” table with common upstream and downstream objects. You can find this table below, as wel as in our user manuals.

 

[wpfilebase tag=file id=1153 tpl=thumbnail /]

 

Ok, but what happens if you are not able to fulfil these requirements? Well, that depends on the application. If it is just trending, you can decide to install the flow meter, but be aware of the additional uncertainty. We can also offer you a CFD simulation if you have a better idea about the flow conditions in the pipe. Contact us for details.

 

My VPFlowScope DP shows a value under the Qmin (minimum) value

How is this possible? The DP has a specified Qmin of 20 mn/sec. Below this value, it is still possible to see flow values, because if internal averaging of the meter and due to the way it is calibrated. During calibration, we set the internal cutoff on 15 mn/sec, which enables you to see fluctuations around 20 mn/sec.

 

 

 

How does the alarm option on the VPFlowscope M work?

The VPFlowScope M features an alarm option for condition monitoring. This alarm option can be configured with VPStudio. Upper, lower or a combination of these boundaries can be set as a condition level. To which of the 3 measurements the alarm is connected is up to the user. One of 3 can be chosen with the preferred unit, e.a.: m3n/hr, bar, SCFM, deg F, Kelvin, and many more.

Download the full application note here: 

Can I connect more than one VPFlowScope to the VPFlowTerminal?

No, the VPFlowTerminal is a one-on-one accessory, it has been designed to connect to a single VPFlowScope and four additional analog sensors (passive loop powered 4 … 20 mA sensors). It contains a main power supply and it shows flow + totalized flow on a three line display.

How do I connect the VPFlowScope to a Modbus RS485 network?

All VPFlowScope mass flow meters are equipped with a Modbus RTU interface. This makes connecting to a modbus RS485 network very easy, provided that you are an experienced modbus user. If not, please visit modbus.org to read more about the basic principles. Or read this application note.

 

What is the connector pin out on the VPFlowScope?

The pin out is the same for both the display module and the connector cap.

 

pinout

See also the user manual.

 

How can I read out the 4 … 20 mA output

The VPFlowScope and VPFlowScope M 4..20 mA outputs are active. This means they provide power to the loop. You can measure the output using a multi meter or PLC or building management system’s IO modules. Check the user manual for details.

 

Which materials get in contact with compressed air?

The wetted materials for all our thermal flow sensors are:

  • Stainless steel (316 and 304)
  • Anodized auminium
  • Glass
  • Epoxy
What are the conversion factors for other gases?

You can use the VPFlowMate and VPFlowScope with various gases, as long as they are non-corrosive and non-explosive.

Examples are:

  • Helium
  • Argon
  • Carbon Dioxide
  • Corgon (C02-Argon)
  • Nitrogen
  • Breathing air mixtures

For oxygen, special caution must be taken and additional regulations/ legislation may be applicable.  The grease in the VPFlowMate and VPFlowScope may not be approved for use with oxygen. Please consult your company on internal safety regulations and make sure that the wetted materials (anodized aluminium, stainless steel 316, glass and epoxy) are approved.

What is the service/ recalibration interval for my flow meter?

We recommend to recalibrate your VPInstruments products annually. But the actual drift of the sensor mainly depends on the pollution rate or certain circumstances. For example:

•  You would want to check your instruments before a major critical measuring project. Let’s say you are an auditor, then you would probably want to check your instruments before you take the plane to the next remote location.
• After an event, especially if your instrument has been dropped on the floor.
• Per requirements: if your company has an ISO 9001 certified quality management system, recalibration for critical measurement systems could be mandatory. Check your QMS on this topic.
• Bi-annually. If you seldom do critical measurements and don’t expose your meter to an event, this can be more cost-effective.

Where can I find the UL listing of VPInstruments products?

A copy of the listing is found below:

VAN PUTTEN INSTRUMENTS B VE231429
BUITENWATERSLOOT 335
2614 AD DELFT, THE NETHERLANDS

Mass flow meters, Series VPFlowMate, Cat. Nos. VPF-Rxxx-Mxxx-Dx-Sxxx-Exxx, may be followed by PN or PN 20, VPP-Rxxx-Pxxx-Dx-Sxxx-Exxx, may be followed by PN PN 20 or PN 40 where x can be any letter/number.

Series VPFlowScope, Cat. Nos. VPS-Rxxx-Pxxx may be followed by PN, PN20 or PN40, where x can be any letter/number.

The actual status can be checked here.  Search for Van Putten Instruments or E231429

Can I use a lage T-piece as an insertion point?

Insertion flow meters are great tools for compressed air measurements. But you have to be careful when installing these devices. The insertion hole has to be as small as possible, otherwise it will create a turbulence around the probe tip. This turbulence can cause misreadings. : in this case, you want to narrow the hole as close as possible to 0,5 inch, plus some tolerance for drilling. If this T-piece is still to be mounted, you can insert a small ring in between the two pipe ends to fill the space.

 

Where do I find VPInstruments’ terms and conditions of sale?

You can download them here:

[wpfilebase tag=file id=103 / tpl=simple]
Why does VPInstruments work with Fedex?

To make the process of shipping our instruments to your locations worldwide both easier, possibly quicker and, perhaps even more important, cheaper. Entering into a collective agreement with one freight management company only (FedEx) will lead to a (sometimes significant) reduction in your shipment costs. Also, you will no longer have to coordinate shipments to your locations as we will take care of all packaging and handling activities end-to-end.

Which invoice will VPInstruments supply with the shipment?

VPInstruments will produce the invoice and attach it to the shipment. The invoice’s total value will correspond exactly with the total sale value of the shipped products.

Which shipping costs will be on VPInstruments’ invoice?

VPInstruments will display shipping costs as an extra order line on your invoice.

Is modbus RTU always included in your flowmeters?

Yes, of course! Modbus RTU is included. All our flow meters are equipped with Modbus RS485 and use the Modbus RTU protocol. The new VPFlowScope M even has Modbus/TCP. So why use old-school 4 … 20 mA when you can have all parameters at once via Modbus?

Further reading on how to connect to a modbus network can be found here.

What do I need to connect a VPInstruments flow meter?

That depends on the application. For auditors, we have a complete start kit, which contains everything you need. For permanent installation in a BMS, we provide power supply modules, junction boxes and cable as separate items. Or you can simply use an M12 cable, and take care of the rest yourself. Contact us if you need help with connecting everything together. We are happy to help you further!

I lost the IP address of my Modbus/TCP converter. How can I recover this address?

In the remote I/O modules we offer for VPInstruments, the IP address can be configured by 3rd party configuration software. Depending on the type of converter, you should go to the original equipment manufacturer, which provides a small software program. This program can sniff/search your computer network and will bring up a list with all devices. On most converters there is also a re-set button which you can use to go back to factory default settings.

VPInstruments uses converters made by ATOP, Anybus, Moxa and other brands. Refer to the original manual of the component for further details on how to re-set or re-configure these products. In the VPVision manual you will find general instructions on Modbus/TCP based I/O modules. See download links for the individual manuals below:

[wpfilebase tag=list id=’109,140′ tpl=data-table pagenav=1 /]

 

What is the recommended installation length for a flow meter?

VPInstruments’ flow meters are calibrated on our proprietary pressurized calibration system, which is unique in the world. Pressurized calibration has many advantages. One of the main advantages is that the calibration conditions are nearly identical to the process conditions in the field. This minimized the total measurement uncertainty. To phrase it simply: It is as accurate as you can get, as long as the flow profile is fully developed and symmetric.

 

Distorted flow profiles

The flow profile in the pipe is probably the biggest enemy to your flow meter’s field accuracy. Pipe bends, elbows, diameter changes, valves will distort the flow profile in the pipe. As the flow meter measures only on one point in the pipe, it cannot “see” these distortions. The flow meter calculates with the ideal, symmetric, fully developed profile.

 

Distorted flow profiles can lead to large measurement errors. So what is the trick: keep enough upstream length before the flow meter and downstream length after the meter. In flow meter terms, we use the term “ X times D” to specify this length. And the X depends on the type of upstream/downstream object. It does not depend on the type or brand of insertion flow meter, as long as it is a single point meter. Only so called “flow conditioners” can reduce the required length.

 

Extensive research has been carried out by various labs, and this has lead to a “generic” table with common upstream and downstream objects. You can find this table below, as wel as in our user manuals.

 

[wpfilebase tag=file id=1153 tpl=thumbnail /]

 

Ok, but what happens if you are not able to fulfil these requirements? Well, that depends on the application. If it is just trending, you can decide to install the flow meter, but be aware of the additional uncertainty. We can also offer you a CFD simulation if you have a better idea about the flow conditions in the pipe. Contact us for details.

 

My VPFlowScope DP shows a value under the Qmin (minimum) value

How is this possible? The DP has a specified Qmin of 20 mn/sec. Below this value, it is still possible to see flow values, because if internal averaging of the meter and due to the way it is calibrated. During calibration, we set the internal cutoff on 15 mn/sec, which enables you to see fluctuations around 20 mn/sec.

 

 

 

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