CS Instruments FA 550 Dew Point Sensor in Aluminium Housing

A rugged IP67 dew point sensor for compressed air and process gases

The CS Instruments FA 550 is a dew point sensor in a robust, waterproof die-cast aluminium housing for compressed air systems and rougher industrial or outdoor conditions. It measures down to -80 degCtd and has an integrated display, alarm relay and 4 to 20 mA output, with Modbus RTU and an optional Ethernet interface.

Typical uses are measuring dew point downstream of adsorption, membrane and refrigeration dryers, and residual moisture in gases such as oxygen, nitrogen, argon, hydrogen, natural gas and biogas. A pressure-resistant version is offered up to 500 bar.

Technical specifications

Configuration and diagnostics

The dew point appears in large figures on the display, and the alarm threshold and hysteresis can be entered through the keys. The analogue output can be scaled freely or assigned to a second parameter such as g/m3. After entering the system pressure and reference pressure, the sensor can calculate back to the atmospheric dew point from the measured pressure dew point. Newer versions offer higher resolution of the sensor signal and on-site diagnosis with a portable device or the CS Service Software.

Choosing the variant and what to confirm

Select the measuring range, the output and bus option, the thread, the maximum pressure and the surface condition. Oxygen service needs the oil and grease free version. For gases under pressure the datasheet lists a stainless steel bypass measuring chamber as an accessory. The datasheet prints the relay rating as 48 VDC in one place and 60 VDC in another, so confirm it before wiring. For a smaller sensor compare the CS Instruments FA 510/515 dew point sensor, or see gas analyzer accessories.

How the CS Instruments FA 550 works

The FA 550 uses a thin-film capacitive sensor. Water vapour from the gas enters a porous layer on the sensor and changes its electrical capacitance. The electronics convert this signal into a dew point, a relative humidity or other moisture values, and show the result on the display and on the outputs. The sensor sits behind a protective cap, so dust and droplets do not reach it directly. A low dew point means very dry gas.

Where the FA 550 is used

• Compressed air downstream of adsorption dryers
• Membrane and refrigeration dryer outlets
• Oxygen, nitrogen and argon lines
• Hydrogen, natural gas and biogas
• Rough or outdoor industrial sites

Selection checklist for the FA 550

• Measuring range, down to minus 80 degrees C dew point
• Pressure range, standard or high pressure version
• Thread: G 1/2, UNF 5/8 or 1/2 NPT
• Output needed: Modbus RTU, 4 to 20 mA or Ethernet
• Alarm relay settings
• Sensor cap: sintered or perforated
• Surface condition, such as oil and grease free
• Measuring chamber and cables

Installation, commissioning and maintenance notes for the FA 550

Fit the sensor in the pipe or in a measuring chamber, in a place where the gas is representative and flows steadily. Wire the 24 VDC supply and the outputs. Set the alarm limit and hysteresis with the buttons. Dew point sensors drift slowly, so plan a regular calibration check against a reference.

Requesting a quotation for the CS Instruments FA 550

Please send the order code options, the range, the pressure, the thread and the quantity. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

FA 550 accuracy

Accuracy is plus or minus 1 degree C from plus 50 to minus 20 degrees C dew point. It is plus or minus 3 degrees C from minus 50 to minus 80.

FA 550 housing

The die-cast aluminium housing is IP67. The screw-in thread is stainless steel 1.4404.

FA 550 display

The display shows the dew point in large figures and has two further pages for other values.

FA 550 Modbus values

Modbus gives pressure dew point, temperature, relative humidity, absolute humidity and ppm values.

FA 550 alarm relay

The relay has an adjustable limit and hysteresis, and is rated at 0.5 A.

FA 550 supply

The supply is 24 VDC with a range of 10 to 36 VDC.

FA 550 accessories

Listed items include measuring chambers, cables of 5 m and 10 m and a wall housing power supply.

Moisture records for the FA 550

Record the dew point trend, the alarm events and the calibration dates.

Choosing the right FA 550 version

Choose the range from the driest dew point your dryer should reach.

Documents and quotation

The attached CS Instruments FA 550 datasheet (2 pages) includes the features, application list, order code scheme, accessories and technical data.

Seven Star LLC is an independent supplier in Muscat. Send the full order code, quantity and delivery location for a quotation.