CS Instruments FA 510/515 – Dew Point Sensor for Compressed Air & Gases

Overview

Industrial Dew Point Measurement

The CS Instruments FA 510/515 Dew Point Sensor is engineered to deliver reliable and continuous dew point monitoring in compressed air systems, process gas lines, and industrial dryers. Designed for both adsorption and refrigeration dryer applications, this sensor enables precise measurement of residual moisture — a critical parameter for maintaining system efficiency, preventing condensation, and protecting equipment from corrosion or process disruption. 

Whether used in compressed air after dryers, membrane systems, or in technical gases such as oxygen, nitrogen, or argon, the FA 510/515 provides accurate, drift-resistant measurement with excellent long-term stability. 

Core Features & Technology

Precision Dew Point Measurement

Using advanced humidity sensing and evaluation electronics, the FA 510/515 produces accurate dew point readings in multiple formats, including pressure dew point [°Ctd] and atmospheric dew point [°Ctd.atm]. 

Versatile Output Interfaces

• 4…20 mA analogue output for direct integration with PLC/DCS and process controllers

• Standard Modbus-RTU (RS-485) digital communication for remote monitoring, diagnostics, and advanced data retrieval

  Both FA 510 (3-wire) and FA 515 (2-wire) versions support flexible installation options. 

Wide Measured Parameters

Through the Modbus interface, users can read multiple humidity and gas parameters, such as:

• Dew point (pressure and atmospheric)

• Temperature (°C)

• Relative humidity (%RH)

• Absolute humidity (g/m³)

• Humidity fraction (g/kg)

• Moisture content (ppm V/V)

• Partial vapor pressure (hPa) 

Sturdy Industrial Design

• Condensation-resistant sensor element for stable and reliable performance

• Fast adaptation time from dry to wet conditions

• IP66 protection class for robust industrial operation

• Pressure tolerance up to ~50 bar in standard versions and optional higher pressure models available

• Threaded process connections (e.g., G1/2″, NPT, UNF) for versatile installation 

Typical Industrial Applications

The FA 510/515 Dew Point Sensor is widely used in:

• Compressed air systems (after adsorption, membrane, or refrigeration dryers)

• Industrial gas process lines (oxygen, nitrogen, argon)

• Plastics industry (granulate dryer moisture measurement)

• HVAC & pneumatic systems

• Process quality assurance and leak detection setups 

By accurately measuring residual moisture and dew point, this sensor helps enhance system efficiency, reduce corrosion and contamination risks, and increase equipment uptime.

Technical Specifications 

FAQ

What is a dew point sensor?

A dew point sensor measures the temperature at which moisture in a gas or air condenses into liquid. This is vital for preventing condensation and ensuring efficient operation of pneumatic systems and dryers. 

What’s the difference between FA 510 and FA 515?

The FA 510 uses a three-wire connection for power and signal, while the FA 515 uses a two-wire connection; both provide a 4…20 mA output and a standard Modbus-RTU interface (on the FA 515 only one of the two can be used at a time). 

Can this sensor measure other humidity parameters besides dew point?

Yes — using the Modbus interface, it can report multiple parameters including relative humidity, absolute humidity, moisture content, and partial vapor pressure. 

Is the sensor suitable for harsh industrial environments?

Yes — with IP66 protection, condensation-resistant design, and robust sensor technology, it works reliably in industrial compressed air systems. 

Choosing Between FA 510 and FA 515

The choice between the two versions mainly depends on your wiring and the input card receiving the signal. The FA 510 is the three-wire version, and the FA 515 is the two-wire, loop-powered version, which is convenient where only a two-core cable is available back to the PLC or dryer controller. Also confirm the measuring range needed: a desiccant dryer outlet normally needs a low dew point range, while a refrigeration dryer outlet sits in a higher range. Check the operating pressure and the thread of the measuring point before ordering.

Installation Guidelines

Correct installation has a strong effect on response time and accuracy. Install the sensor downstream of the dryer, preferably with a measuring chamber and a small constant bleed flow so the sensor sees representative gas. Avoid dead legs, low points where condensate collects and mounting directly after a drain. Do not install the probe in a location with liquid water or oil aerosol, and use a suitable filter where compressor oil carry-over is possible. Tighten the thread using the wrench flats, never the housing, and route the M12 cable away from power cables.

Integration with Control Systems

The 4…20 mA signal connects directly to a PLC, DCS or chart recorder. When the standard Modbus-RTU interface is used, several sensors can share one RS-485 line, and additional parameters such as temperature and ppm V/V become available to a SCADA or energy monitoring system without extra transmitters.

Maintenance and Calibration

Dew point sensors should be checked against a reference at regular intervals, commonly once a year for critical compressed air quality points. A slow response or readings that are wetter than expected usually indicate a problem at the measuring point, such as a missing bleed flow or contamination, rather than a sensor fault. Keeping a spare, pre-calibrated FA 510/515 lets you swap sensors during calibration without losing monitoring.

Applications in Oman and the GCC

High ambient temperatures and humidity along the coast place a heavy load on compressed air dryers. Continuous dew point monitoring helps plants in Muscat, Sohar and Duqm protect instrument air, pneumatic valves and process equipment.

Order Numbers and Accessories

CS Instruments lists four standard versions. The FA 510 (3-wire) is order number 0699.0510 for -80 to +20 °Ctd and 0699.0512 for -20 to +50 °Ctd. The FA 515 (2-wire) is 0699.0515 for -80 to +20 °Ctd and 0699.0517 for -20 to +50 °Ctd. The manufacturer recommends the low range after adsorption dryers and the high range after refrigeration dryers. Each sensor is delivered with a 5-pin, A-coded M12 connector socket and a calibration certificate, and all standard versions are rated for up to 50 bar.

Accessories named by the manufacturer include the standard measuring chamber for compressed air up to 16 bar (0699.3390), a high-pressure measuring chamber up to 350 bar (0699.3590), a measuring chamber for atmospheric dew point (0699.3690), connection cables of 5 m (0553.0104) and 10 m (0553.0105), and the CS Service Software with PC connection set (0554 2007) for changing Modbus settings and output scaling. Special output scaling in g/kg, % RH, mg/m³, ppm (V/V) or g/m³ is listed under 0699.4004, and a precision calibration at 0 and 10 °Ctd with ISO certificate under 3200.0003.

Wiring, Outputs and Installation Limits

On the FA 510 the M12 connector carries the supply on pins 1 and 3 (10 to 36 VDC), RS-485 A and B on pins 2 and 4, and the 4…20 mA signal on pin 5, so the analogue output and Modbus-RTU can be used in parallel. The FA 515 also has both outputs, but because it is a low-power 2-wire device only one can be used at a time, and changing between them requires the CS service software. Modbus is shipped with ID 1, 19200 bps, even parity and 1 stop bit. The analogue load must stay below 500 Ω.

Direct installation into the pipe is only allowed when the system is unpressurised; the sensor is tightened to 25 to 30 Nm, and a sealing ring must not be used on the NPT 1/2 inch thread. CS Instruments recommends indirect installation with a measuring chamber on a quick coupling, where compressed air flows continuously at about 1 l/min (expanded, at 7 bar), which shortens response time and allows removal without interrupting the line. A pre-filter is advised where the air contains oil or dirt particles. The manufacturer asks for calibration at regular intervals, at the latest after two years.

Sourcing from Seven Star LLC

Seven Star LLC supplies CS Instruments dew point sensors and accessories across the GCC and can help match the correct version to your dryer and control system.

Request a Quote for CS Instruments FA 510/515 – Dew Point Sensor for Compressed Air & Gases

Enhance your compressed air and gas system performance with the CS Instruments FA 510/515 Dew Point Sensor — contact Seven Star LLC for quotes, calibration options, integration support, and technical details. 

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