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CS Instruments FA 550 Dew Point Sensor

  • Robust IP67 enclosure
  • Adjustable alarm output
  • Dual 4 - 20 mA output for dew point and temperature.

The FA 550 from CS instruments is a durable, rugged dew point transmitter offered in a waterproof die-cast aluminium housing with an IP67 rating, ideal for outdoor or harsh environments.

A wide temperature measuring range with options from -80 °c to +50 °c with scalable outputs within this range, see the specification sheet for full measuring range options.

Accuracy of the sensor is stated as ± 1 °C at +50 to -20 °Ctd, ± 2 °C at -20 to -50 °Ctd and ± 3 °C at -50 to -80 °Ctd.

There are many output options available including single (dew point) and dual (dew point and temperature) 4 – 20 mA outputs.

Modbus-RTU is available over RS 485 or Modbus / TCP is available over an ethernet interface, optionally with PoE (Power over Ethernet).

A programmable alarm relay can also be programmed act as a low or high threshold alarm.

The integrated display allows for easy programming of process parameters, alarm threshold or output scaling, additionally devices can be supplied as blind units.

The sensor can be supplied with either a stainless steel sintered cap (~ 50 μm) or a perforated stainless steel cap.

Process connections

Process connections available are either ½” BSPP of UNF 5/8”

Output data

Devices with Modbus-RTU also offer additional data via the digital interface which includes:

  • Pressure dew point [°Ctd.]
  • Temperature [°C], rel. humidity [% RH]
  • Abs. humidity [g/m³]
  • Degree of humidity [g/kg]
  • Moisture content V/V [ppmV/V]
  • Partial vapour pressure [hPa]
  • Atmospheric dew point [°Ctd.atm]

Key specifications

Measuring ranges-80…20 °Ctd, -60…30 °Ctd,-20…50 °Ctd, or 0…100% RH
Accuracy± 1 °C at 50…-20 °Ctd
± 2 °C at -20…-50 °Ctd
± 3 °C at -50…-80 °Ctd
Pressure range-1…50 bar
Special version up to 350 or 500 bar
Power supply24 VDC (10…36 VDC)
Protection classIP67
EMCIn acc. with DIN EN 61326-1
Operating temperature-20…50 °C
Modbus-RTU, 4…20 mA active (not electrically isolated),alarm relay (max. 48 VDC, 0.5 A)
Refer to order code on the spec sheet
Burden< 500 Ω
MaterialDie-cast aluminum housing, sensor tube stainless steel 1.4571
Screw-in threadG 1/2″, optional 5/8" UNF


Common process applications and industrial uses include:

  • Dew point measurement in the compressed air after adsorption dryers/membrane dryers and refrigeration dryers.

  • Residual moisture measurement / dew point measurement in gases such as oxygen, nitrogen, argon, hydrogen, natural gas, biogas.

Other features

  • Optional special cleaning, oil and grease free (e.g. for oxygen applications)
  • Optional silicone-free version including special cleaning oil- and grease-free
  • Optional precision calibration at -40 °Ctd or 3 °Ctd incl. ISO certificate
  • Standard measuring chamber for compressed air up to 16 bar
  • High pressure measuring chamber up to 350 bar available.

Model numbers

  • 0699 0550


The CS Instruments FA 550 Dew Point Sensor is widely used in the following industries:

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