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VKG-3T - gas amount calculation unit


The calculation unit is intended for transduction of output signals of natural gas temperature, pressure and flow rate or volume measuring transducers to their indications and calculation of gas volume brought to standard conditions as well as recording technological parameters: pressure, differential pressure, temperature.
Calculation unit is not intended for working in explosive areas and premises.
Application field
Calculation unit as a part of measurement complexes is used in control and measurement on one or two gas pipeline including accounting and calculation operations of natural gas consumption in different industry fields.

Functional capabilities

Gas amount calculation unit VKG-3T ensures measurement, calculation and recording the following parameters on indicator and external devices:
  • Current and average pressure, temperature, flow rate and volume values in operating and standard conditions;
  • Total (summary) volume values in operating and standard conditions;
  • Current and average values of technological parameters;
  • Results of violations diagnosis of specified gas parameters variation ranges;
  • Results of diagnosis of violations connected with meter cut off and magnetic field influence;
  • Calculation unit self-diagnosis results;
  • Indicating pressure values in any units - MPa, KPa or kg/cm2;
  • Calendaring.

Gas amount calculation units VKG-3T when diagnosable situations are present ensure change of measurement algorithm according to specified conditions.
Calculation unit has two extra outputs ensuring remote transmission of information about gas volume and presence of diagnosable situations to external devices.
Calculation unit has additional input ensuring recording control sensor signal, such as for example gas contamination sensor, fire alarm sensor etc.
Gas amount calculation units VKG-3T ensure measurement of up to 4-5 technologic values (pressure or differential pressure) from sensors with output current signal
(4-20) mA.
Calculation unit is powered from integrated lithium-type battery, battery service life – 4 years.

Information recording

Recording average gas parameters values, technological parameters, gas volume calculation time and calculation end time: archive depth – 1,448 hours, 125 days, 44 decades, 24 months.
Recording volumes, calculation time and calculation end time with cumulative sum.
Recording of diagnosable situations and changes in setup database.
Archive and resulting parameter values as well as setup database of the calculation unit are energy-independent. Archives of diagnosable situations and changes in setup database don't depend from user actions.

Metrologic characteristics

Registered parameter

Indication range

Limits of
permissible error



(-40 - +70)°С

± 0.1°С

Absolute error

Pressure, differential pressure

(0 - 16) MPa

± 0.1%

Conventional error

Operating flow rate

(0 – 999999) m3/h

± 0.5%

Relative error

Standard flow rate

(0 – 999999) m3/h

± 0.05%

Relative error

Operating volume

(0 – 999999999) m3

± 1 unit .m.r.

Absolute error

Standard volume

(0 – 999999999) m3

± 0.05%

Relative error



± 0.01%

Relative error

Algorithm of calculation of flow rate and volume values brought to standard conditions comply with requirements of PR.50.2.019. Gas compressibility coefficient calculation is performed according to NX 19 method or constitutive equation GERG-91 under GOST 30319.2.

Limits of permissible errors of VKG-3T for transducing output signals of gas parameter sensors:

Measured value

Limits of permissible error


Dtв = ± 0.05; ± 0.1°С (absolute error)

Pressure, differential pressure

dр = ± 0.2 % (conventional error)

Volume in operating conditions

dv = ± 0.01 % (relative error)

Compensation factor (volume in standard conditions)

dc = ± 0.02 % (relative error)

Calibration interval - 4 years.

Measuring channels

  • 2 resistance measuring channels (when 1 channel is used, 2 can be used for temperature measurement in technological purposes);
  • 8 current measurement channels (4 - 20) mA (2 channels - gas pressure, 1 channel - barometric pressure, 5 channels - pressure or differential pressure in technological purposes);
  • 2 pulse number (frequency) measurement channels.

Connected sensors

Gas amount calculation units are intended for working together with the following measurement transducers:
  • Gas volume (flow rate) with output pulse signal with frequency up to 1,000 Hz of TZ, DELTA, TRZ, RVG, SG, LG-К, RG-К, VIR-100, DRG.М type etc; 
  • Pressure (excess, absolute) and differential pressure with output current (4-20) mА;
  • Resistance under GOST 6651 with  unique sensor curve (USC) 100P, Pt100, 500P or Pt500  (USC choice is applied to both resistance measuring channels);
  • Gas meters (flow meters) with passive output circuit ("dry contact" type) and pulse frequency up to 16 Hz or with active output circuit and frequency up to 1,000 Hz.


Measuring information via RS232, RS485 or Ethernet (determined in the order) interface can be sent to external devices: printer, modem, storage panel, computer.

Warranty period

Warranty period - 6 years.