Specific Gravity Transducer for Gases

LFE Specific Gravity TransducerLFE’s OEM specific gravity transducer was designed for the continuous, on-line analysis of a gas stream.

The advantages of this transducer, in addition to low cost and relative simplicity, are it's high intrinsic linearity, long term stability and short response time.

LFE's specific gravity transducer is implemented in end-user products, and sold exclusively by our partner Union Instruments GmbH in Karlsruhe, Germany.

  • Functional Principle
  • Technical Data

Functional Principle

The instrument utilizes an acoustical principle whereby a transmitter membrane vibrating sinusoidally at a constant frequency and amplitude transfers it’s motion to the gas in the sample chamber. The pressure amplitude received at a pressure transducer in direct proximity is directly related to the density of the gas sample.

Specific gravity of gases

The propagation of the sound waves in the analyzer chamber is in general not only a function of the gas-density, but is also influenced by other gas parameters such as viscosity and heat capacity. The analyzer's high selectivity to the density is the result of proper chamber geometry, dimensioning and operational parameters.

One key to long term stability is the reference chamber which is exposed to ambient air under atmospheric pressure conditions. The signal obtained from the reference chamber is used in a control loop to regulate the amplitude of the vibrating transmitter membrane.

Technical Data

Property Specifications
Measured quantity online, continuous specific gravity analysis of a sample gas stream
Measurement principle Transferred amplitude of sound waves (constant frequency) propagating through the gas between a transmitter and receiver
Range 0.2 - 2.2 (optional: 0 - 2.0 )
SG: specific gravity relative to air
Signal output 0 - 5V
Resolution <±0.01 ΔSG  (<±0.5 %FSO)
Linearity btwn. SG 0 - 1.5:  <±0.02 ΔSG   (<±1 %FSO)
btwn. SG 0 - 2.0:  <±0.04 ΔSG   (<±3 %FSO)

Technical specifications subject to change without notice