Monday 16 September, 2019
Home About Us News A digital alternative to traditional VA-meters or Purge meters

A digital alternative to traditional VA-meters or Purge meters

medical equipment  the gas rotameter

The first Variable Area (VA) meter with rotating float was invented by Karl Kueppers in Aachen in 1908. The device was patented in Germany that same year. Felix Meyer was among the first to recognize the significance of Kueppers’ work and implemented the process for offering the meter for sale. In 1909, the firm of “Deutsche Rotawerke GmbH” was created in Aachen (Germany). They improved this invention with new shapes of the float and of the glass tube. It didn’t take long for the new device to capture attention in Europe, the United Kingdom, and other areas.

Over time, different types of VA flow meters (also called purge meter) have been developed, usually in response to some specific need. Nowadays a VA flow meter usually consists of a tapered tube, typically made of glass or plastic. Inside this tapered tube there is the ‘float’ which is made either of anodized aluminum or a ceramic. The ‘float’ is actually a shaped weight that is pushed up by the drag force of the flow and pulled down by gravity. The drag force for a given fluid and float cross section is a function of flow speed squared only.

While the meters are still relatively simplistic in design, relatively low cost, low maintenance and ease of installation they are widely used in many kinds of application. Despite these facts, the traditional VA meter has a number of drawbacks. For instance, graduations on a given VA meter will only be accurate for a given substance at a given temperature and pressure. Either way, due to the direct flow indication, the resolution is relatively poor anyway. Especially when they are built into a machine, reading might be hard. Moreover, the float must be read through the flowing medium, so you can imagine that some fluids may obscure the reading.

9 reasons why to use a thermal mass flow meter instead of a traditional VA meter
As for the current century, Bronkhorst developed the MASS-VIEW® series which is the digital high-tech alternative to these traditional VA meters. Thanks to today’s digital possibilities, many other advantages arises for many industrial processes and chemical plants.

  • The digital OLED display provides an easy direct or relative reading of the actual flow. Herewith parallax errors are excluded.
  • In contrast to the traditional VA meter which need to be mounted in a vertical position, this digital alternative can be mounted in any position.
  • Rather than measuring the volume flow it measures the actual mass flow.
  • The flow path is made of sustainable aluminum rather than plastic or glass which is fragile.
  • The instruments are standard equipped with 0-5V, RS-232 and Modbus-RTU output signals. Note that the traditional VA meters usually do not have any output signal available at all.
  • As a standard feature, there are 2 built-in relays which indicate an alarm situation. Herewith, external devices can be controlled.
  • Multi Gas; As opposed to traditional VA meters, which are produced for one particular fluid only, the digital alternative has up to 10 pre-installed gasses available as a standard feature.
  • Multi Range; As opposed to traditional VA meters, which usually have a rangeability of 1:10 and one single full scale range only, the digital alternative has a rangeability of 1:100 as well as up to 4 pre-installed flow ranges.
  • The accumulated flow rate is easily obtainable and supplied as a standard feature.

   

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