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Measuring services

Many firms are offering short- and long-term consumption protocollings with our devices. Their offer includes all necessary actions to be done, e.g. the installation of the measuring nozzles in the line system, the measurements, the protocolling of the measured values and the removal of weaknesses and leakages.

Please ask, e.g., for informations on the Energy Saving" program of FESTO (see also directly here, PDF-file, 60 KB).

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Additional media

Besides of the preselected gases and liquids in setup mode, the VSM-02 can be used to measure many other gases as well. To serve this purpose in setup mode there is a feature to enter the individual gas constant manually, along with the standardized density at 15 °C. The parameters of several useable gases can be found in the table below.

Gas Gas constant
in J/kgK
Std. density
in kg/m³ bei 15 °C
Ammonia, NH3 488,148 0,7313
Argon, Ar 208,147 1,6907
Helium, He 2076,961 0,1692
Carbon monoxide, CO 296,819 1,1849
Carbon dioxide, CO2 188,906 1,8740
Carbonyl sulfide, COS 138,392 2,5793
Air 287,091 1,2254
Neon, Ne 411,940 0,8531
Oxygen, O2 259,819 1,3546
Sulfur dioxide, SO2 129,772 2,7740
Carbon disulfide, CS2 109,188 3,2943
Nitrogen oxide, NO 277,059 1,2705
Dinitrogen monoxide, N2O 188,887 1,8774
Nitrogen, N2 296,761 1,1854
Nitrogen (air) 295,250 1,1916
Water vapor, H2O 461,484 0,7620

For your safety: many technically important gases are inflammable or explosive. Please never use the VSM-02 basic model in order to measure such gases !

The explosion protected version of the VSM-02, however, can be used to measure even more gases, e.g.:

Gas (with VSM-02/EX only!) Gas constant
in J/kgK
Std. density
in kg/m³ bei 15 °C
Acetylene, C2H2 318,816 1,1107
Ethane, C2H6 276,490 1,2863
Ethylene, C2H4 296,358 1,1948
Benzene, C6H6 106,442 3,3036
N-butane, C4H10 143,041 2,5899
Isobutane, C4H10 143,041 2,5090
Butene, C4H8 148,179 2,3731
Chlorine, Cl2 117,239 3,0469
Hydrogen chloride, HCl 228,006 1,5539
Hydrogen cyanide, HCN 307,626 1,1608
Cyanogen, C2N2 159,771 2,2270
Methane, CH4 518,235 0,6795
Methyl chloride, CH3Cl 164,664 2,1873
Propane, C3H8 188,544 1,9050
Propylene, C3H6 197,566 1,8154
Hydrogen sulfide, H2S 243,942 1,4562
Toluol, C7H8 90,241 3,8967
Hydrogen, H2 4124,110 0,0852
Xylol, C8H10 78,316 4,4900

As a matter of course, ordinary air can also be measured with the VSM-02. Throughout the industry the so called compressed air is widely used as a means to transport mechanical energy. The importance of compressed air for this special use was the reason to produce a specialized version of the VSM-02, the so called RectuTest RT-02. In opposition to the VSM-02, the RT-02 could only be used to measure compressed air, but this was compensated by the additional consultive competence of our sales partner who maintained local sales offices in many countries and was specialized in the industrial application of compressed air.

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Gas mixtures

The volume flow of mixtures of several gases can be measured precisely by the VSM-02. All that is needed is to know the average density and the average gas constant of the mixture. Both values can be entered comfortably in SETUP-mode. If your browser has JavaScript enabled, you can use the calculator below in order to find the necessary setup values from the gases in your particular application. Please choose the gases from the selection box and push the 'Add'-button to bring them into the table.

Mixture component Vol.%Gas selection
Mean Density [kg/m³]
Mean Gas Constant [J/(kg*K)]

Hint: The values in the column 'Vol.%' must sum up to 100 %. If this is not the case, the entered values will be automatically scaled to 100 % on clicking the 'Calculate'-button, thus overwriting the originally entered values in most cases. Therefore please push this button, if possible, only after you have entered all gases.

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Pressure losses and Nozzle selection

The volume flow is measured with the help of a slight pressure drop in our measuring nozzles (the so called effective pressure). A considerable amount (approx. 2/3) of this pressure loss is regained, however. So, together with the high sensitivity at low effective pressures, with a correctly chosen nozzle diameter it is the rule, rather than the exception, to have only minimal remaining pressure losses. If your browser has JavaScript enabled, you can use the calculator below (which uses compressed air as an example) in order to see for yourself, how high or low the remaining pressure losses would be in your application. Just enter a value in the field "Volume flow", press the "Calculate" button and, maybe, play a bit with different nozzle diameters in order to see how pressure losses can further be minimized.

Temperature Line overpressure Nozzle selection
Volume flow Unit
Pressure loss Remaining pressure in %

In case the calculator only presented you the messages "Nozzle too small" or "Nozzle too big": we offer numerous other nozzles as well, starting presently from 0.2 mm and going up to 10 inches in diameter. This allows the use of the VSM-02 and VSM-3K in nearly all practically imaginable applications and dimensions of volume flows.

One of our smallest nozzles 2 inch is a very common nozzle size
0.2 mm nozzle, max. 0.07 m³/h 2" nozzle, max. 2000 m³/h
A 10 inch nozzle is, by no means, our size limit The shown ensemble already covers a huge flow range
10" nozzle, max. 60,000 m³/h Measuring from 0.02 l/min to 60,000 m³/h,
i.e. over a range of 1:50 millions

Hint:The outstanding scalability of the VSM-02 is due to the use of different measuring nozzles. Without the need to change the measuring nozzle, however, the new VSM-3K offers a contiguous measuring range of at least 1:3000 already at ambient pressure, at higher line pressures a ratio of 1:6000 and even more can be reached. These properties are world-wide unique. In plain words: changing a nozzle is always associated with some effort, time, work and costs. Eventually the supply must be interrupted for a longer time, causing additional, sometimes much higher costs. The VSM-3K, on the other hand, usually doesn't require any nozzle changes. Even at a regular flow of, e.g., 60,000 m³/h the VSM-3K can still identify flows as low as 10 m³/h, which one would consider to be a small leakage at the given scale. At no time the supply needs to be interrupted. You will get no standstills, no additional costs, but a pretty good leakage overview in addition to the regular consumption measurements.

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Backup service

You want to restore the factory settings in a VSM-02, but can't find the original disk? No problem,we retain a backup from every device. Just send us an email with the serial number of the VSM-02 and the requested backup copy comes in return.

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Software-Update f. RT-01

The RT-01 was a predecessor of the VSM-02 For the older model RT-01 (compressed air) you can download an update of its PC/link-programm (version 1.6, approx. 800 KB). Unpack the ZIP-file to an own directory and start the installation from there (SETUP.EXE). Besides, there is also the possibility to upgrade the RT-01 firmware to version VSM-22.

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