Bronkhorst

Top 5 FAQ about the MASS-VIEW digital flow meter series

May 25, 2021 Frank Doornbos
digital flow meter calibration

In my previous blog post ‘A digital alternative to traditional VA-meters/purge meters’ I shared the ins and out about our MASS-VIEW flow meter series, a digital alternative to traditional VA-meters or purge meters.

Today, I would like to share the top 5 digital flow meter questions we often receive from our customers:

  1. Can I use the MASS-VIEW digital flow meter for gas mixtures?
  2. Can I use the MASS-VIEW digital flow meter at sub-atmospheric pressure conditions?
  3. Will the accuracy of my instrument be affected by dust, humidity, or oil mist in the process gas?
  4. How often should I calibrate my instrument?
  5. How can I hook up the alarm settings of a digital flow meter?

1. Can I use the MASS-VIEW digital flow meter for gas mixtures?

Since the introduction of this digital flow meter series, I have regularly been asked whether the instrument is suitable for gases or gas mixtures that are not stored in the instrument by default.

Despite the fact that the pre-installed gases might be the most common gases the MASS-VIEW is used for, the wetted parts of the instruments allow to use them for other gases or gas mixtures as well.

In general, it is possible to apply a fixed conversion factor to the measurement of the MASS-VIEW, calculated with the free online calculation tool. Besides that, you can also use the FluidAdd tool from Mass Flow ONLINE, which is an additional calculated fluid curve. This tool allows you to overwrite one of the default gases.

Working principle of the digital flow meter

Working principle of the MASS-VIEW digital flow meter

The creation of a FluidAdd file requires the following information specified by the user:

  • Conversion factor: The calculation of the gas conversion factor can be made via FLUIDAT® on the Net using the CFMassView module.
  • Standard density: You may check Fluidat® on the Net for the correct data. The density is needed to show the flow not only in normalised volume flow units (like ln/min or ls/min) but also in mass flow units like g/h.
  • Serial number of the instrument: This information is required to make sure that the FluidAdd file is adopted to the instrument.
  • Custom gas name: The custom gas name will be shown in the list of selectable gases in the instrument.
The new calculated curve will be sent by email and can easily be uploaded to the flow meter.

digital flow meter (MASS-VIEW) in an application
Example of digital flow meter MASS-VIEW in an application

2. Can I use the MASS-VIEW digital flow meter at sub-atmospheric pressure conditions?

To answer this question properly, it is actually required to start with a closer look at the physical properties of gases. In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Considering a sub-atmospheric flow rate, you can imagine that the gas flow rate needs to be (significant) higher to transport a particular amount of gas (mass).

Since the MASS-VIEW series operate on the principle of direct thermal mass flow measurement, the combination of its structural design and the increased (volumetric) gas flow rate in sub-atmospheric conditions might have negative side-effects to ensure a proper measurement. Therefore, the measurement output cannot be guaranteed in sub-atmospheric conditions.
 

3. Will the accuracy of my instrument be affected by dust, humidity, or oil mist in the process gas?

Humid air for instance can be seen as a mixture of water and air and additionally to this, dust and oil might be present in the process gas. The physical properties of those mixtures will differ from those of dry and clean air. As from a technical point of view, this flow meter series is able to deal with the humidity as long as there is no condensation inside the flow channel. However, the inaccuracy of a thermal mass flow meter calibrated for dry air could increase when humid air is applied instead of dry air.

As for the oil and dust; potential clogging of a thermal mass flow instrument in general is just around the corner. However, the thru-flow nature of MASS-VIEW’s working principle from Bronkhorst is relatively insensitive to possible clogging in potentially polluted industrial gas applications. However, the insensitiveness does not mean that clogging is impossible. It is highly recommended to filter those process gases before it enters the mass flow meter.

4. How often should I calibrate my instrument?

Mass flow instruments, in fact all process instruments, experience wear from the conditions of the process in which they are installed. Temperature, electronic component tolerance shift, contamination built up over time (even very slight), plus other factors will all contribute to affecting the accuracy of an instrument.

Your instruments should regularly undergo a calibration check if not a recalibration. But how often? Because the nature of each application is different (conditions, running time, etc.) a calibration interval can last three years or three months.

Bronkhorst instruments do not have specified due dates for calibration. We suggest that our instruments be calibrated every year. However, based on the application conditions, and perhaps company quality procedures, each customer must determine when they need to send in an instrument for recalibration.

Properly calibrated instruments will be more accurate, more reliable, help ensure consistency, and help improve production yields.

5. How can I hook up the alarm settings of a digital flow meter?

These digital flow instruments have built-in programmable alarm functions available to make the flow meters as versatile as possible. These functions enable the user to get warned for or in cases of:

  • System errors
  • System warnings
  • Min/max alarms
  • Response alarms
  • Batch alarm
  • Master slave alarms

When alarm settings are activated, the flow alarm will automatically open or close Alternating Current (AC) electrical circuits, activating warning lights, bells, pumps or other process control equipment. In fact, today’s highly flexible and versatile alarm trips can be found working in a wide range of applications, under an impressive list of pseudonyms.

As a standard feature, the MASS-VIEW flow meter has two alarms connected to a relay/switch. One side of the switch is connected to ground (pin 4, 0 Vdc)  and the other side is connected to Pin 3 (alarm high).
 

One side of the switch is connected to ground (pin 4, 0 Vdc) and the other side is connected to Pin 3 (alarm high).

connection diagram - digital flow meter
Connection diagram 1

The other relay is also with one side connected to ground (pin4, 0 Vdc) and the other side is connected to Pin 5 (alarm low).

connection diagram - digital flow meter
Connection diagram 2

Would you like more information about digital flow meters?

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Bronkhorst High-Tech B.V.

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NL-7261 AK Ruurlo (NL)
Tel. +31 573 45 88 00
[email protected]

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