Produkt-Neuheit

A high sensitivity hot wire, low power semiconductor type gas sensor ideal for use in portable detection devices

Applications

Acetone sensors are used in a variety of industrial and medical applications to determine the amount of acetone present.

Industrial applications:

• Printing industry (e. g. as a solvent for printing inks)
• Paint thinner and remover
• Cleaning agents (e. g. for cleaning and degreasing machines and equipment)
• Manufacture of chemicals (e. g. for plastics, medicines)
• Textile industry (e. g. synthetic fiber production)
• Cosmetics production

Monitoring acetone levels in industrial settings is crucial due to its high flammability and potential health risks. Fire and explosion hazards are high, particularly in confined spaces where vapours can accumulate. Occupational exposure limits are established to protect workers from over exposure to acetone; for instance, OSHA's permissible exposure limit (PEL) for acetone is an average 1000 ppm over an 8 hour period.

Medical applications:

Low levels of acetone are produced naturally by the human body and are present in both blood and exhaled air, some health conditions will cause these levels to rise. For example, in diabetic patients the level of exhaled acetone is over 1800 ppb compared with 300-900 ppb in healthy humans.

Measurement of acetone in exhaled breath can be used for:

• diagnostic control of a patient's diabetic condition.

• For diagnosis of certain conditions and as a marker to follow the effectiveness of treatments e.g. for metabolic disorders and lung cancer.

• Measurement of the rate of fat loss in healthy individuals

TGS1820 construction and operation

The TGS1820 is a compact semiconductor hotwire gas sensor with high sensitivity and selectivity to acetone. The sensor element consists of a platinum heater coil embedded in a small bead of metal oxide semiconductor (MOS) sensing material. Gas adsorption on the surface of the semiconductor causes a change in electrical conductivity, this can be measured between the two ends of the heater coil as a change in the combined resistance of the MOS semiconductor and the heating coil.

The TGS1820 has a high sensitivity to acetone with very low cross-sensitivity to ethanol and hydrogen. This feature makes the sensor ideal for acetone analysis in breath.

Basic measuring circuit of the TGS1820:

The basic measuring circuit (principle of a Wheatstone Bridge) of the TGS1820 is shown in the down loadable pdf .

Circuit voltage is applied between the ends of the sensor and a load resistor which are connected in series. The applied circuit voltage also serves as the heating voltage, this is 2.3 ±0.05V in the case of the TGS 1820. It is important that the load resistor connected in series can maintain the sensing element at a specific temperature optimal to sensing acetone, under standard circuit conditions this will be approximately 10Ω.

The voltage at the sensor output of the TGS1820 (= bridge output), consisting of the sensor, a load resistor and two opposing resistors, is measured with a voltmeter as shown in the basic measuring circuit:

Vb = VRL - VREF


(Note that the response of the sensor can also be monitored using a high-resolution voltmeter without a Wheatstone bridge circuit by measuring the voltage changes across the load resistor.)


Figaro Engineering offers extensive technical data and information for the TGS1820 in addition to an evaluation module:

https://www.figaro.co.jp/en/product/feature/tgs1820.html