Compressed Air Oil Monitor

Sigma 120 Portable compressed air Oil Monitor

with 5" touch screen, 0.003 mg/m³, 4...20 mA output, RS-485, alarm output, 24 VDC, transport case, connectable to S 551


The new residual oil monitor Sigma 120 monitors oil contents of compressed air and gases can be used for spot checks as a portable unit, but also as a permanent installation unit. The simple installation and the outstanding performance makes Sigma 120 the ideal choice when residual oil contents needs to be measured and monitored.

Oil free compressed air is not an easy task to be achieved. Monitoring is a must in many industries and applications to avoid contamination in products and risks for health of humans. S 120 makes this monitoring task affordable and reliable.

For best accuracy and long term stability, the sensor applies an automatic calibration. Sensor contamination and sensor life time are monitored and will be indicated to the user. An over range detection will remove the sampling air from the sensor to protect it against contamination.

Limits of oil vapor

  • Compressed air class 1 (EN ISO 8573-1): 0.01 mg/m³
  • Medical applications (EAB 407/1238): 0.1 mg/m³
  • Breathing apparatus (EN 12021): 0.5 mg/m³


  • Measures residual oil contents in compressed air and other gases
  • Can be used for permanent or in portable applications
  • Measures down to 0.003 mg/m3
  • Easy connection through sampling hose and quick connect
  • Output signals:
    - 4...20 mA
    - RS-485 / Modbus / RTU
    - Relay switch (NO)
  • PID sensor for highest accuracy
  • Service and Alarm indication through LED
  • Connectable to our displays and data loggers as well as third parties displays and control units


  • Medical air
  • Pharmaceuticals
  • Breathable air
  • Marine air
  • Food and beverage
  • Medical engineering
  • High speed trains
  • Semiconductor fabs
  • Conveyance of hygroscopic food
  • High tech processes
  • Electronics industry

Technical information

Measuring range:         -0.003...10 mg/m3
Sensor type:                 PID (photoionization detector)
Medium:                       Clean dry compressed air
Operating pressure:    3...15 barg
Sample flow rate:        < 2 l/min
Life time sensor:         Requires service once a year
Gas temperature:        -20...40 °C
Ambient temperature: -20...40 °C