SN45-R14HDCRQ SN45-G12HDCRQ SN55 FS110 CATO Flow Switch 100 bar

Product Overview

The SN45/SN50/SN55 series electronic flow switches and FS110 series flow sensors are thermal flow switches engineered by CATO (or other OEM brands) for industrial fluid monitoring applications. They are widely used for flow monitoring in hydraulic systems, pneumatic systems, cooling water circuits, cutting fluids, lubrication oils, and pump dry-run protection.

The SN series operates on the thermal principle: two resistors are enclosed in a sealed probe—one heated as the sensing resistor, the other unheated as the reference resistor. When the medium flows, heat is carried away from the heated resistor, changing its resistance value. The difference between the two resistors is used to determine flow velocity.

The SN series features all-stainless steel probe and housing, IP67 ingress protection, and pressure resistance up to 100 bar. With no moving parts, maintenance-free operation, and easy installation, a single model accommodates multiple pipe diameters. A 6-LED bar display provides intuitive visual indication of flow trend and switch status.

Our complete range of CATO SN/FS series flow switches strictly adheres to OEM technical standards, achieving 100% direct interchangeability with original components. Every unit undergoes 100% simulated operating condition bench testing prior to shipment, ensuring performance parameters are fully consistent with genuine CATO products. Direct replacement significantly reduces equipment downtime and maintenance costs.

⚠️ Brand and Model Attribution Note:

• SN45/SN50/SN55 series belong to the CATO brand, with B+B (Germany) and other OEM manufacturers also producing similar products

• FS110 series is a derivative model of the SN series, with some models labeled as FSK6-FS110 series

• The original title’s reference to “Electronic Pressure Switch” is descriptive—the actual product is an electronic flow switch (Flow Switch) , not a pressure switch

⚠️ Model Code Decoding (using SN45-R14HDCRQ as example) :

• SN = Series code (SN45/SN50/SN55)

• 45 = Specification/size code

• R14 / G12 / G14 = Thread connection specification (R14=G1/4; G12=G1/2; G14=G1/4)

• HDC / HDP = Configuration code (HDC=standard; HDP=special configuration)

• RQ / RQ30 = Design variant/electrical configuration code

Technical Specifications 

SN45 Series General Specifications

• Product Series: CATO SN45 series electronic flow switch

• Brand: CATO (or other OEM brands)

• Product Type: Thermal flow switch

• Operating Principle: Thermal principle (heated resistor + reference resistor differential detection)

• Setting Range (Water) : 1 – 150 cm/s

• Setting Range (Oil) : 3 – 300 cm/s

• Setting Range (Air) : 20 – 2000 cm/s

• Signal Output: PNP / NPN / Relay (SPDT N/O + N/C)

• Supply Voltage: 24V±20% DC or 230V±15% AC

• Switching Current (PNP/NPN) : Max. 400 mA

• Switching Current (Relay) : Max. 4 A

• No-load Current: Max. 80 mA

• Flow Indication: 6-LED bar display

• Setting Method: Potentiometer adjustment

• Pressure Resistance: 100 bar

• Temperature Gradient: ≤4°C/s

• Response Time: 1 – 13 s, typical 2 s

• Initialization Time: Approx. 8 s

• Electrical Protection: Reverse polarity, short-circuit, overload protection

• Ingress Protection: IP67

• Media Temperature: -20°C to +80°C

• Ambient Temperature: -20°C to +80°C

• Storage Temperature: -20°C to +100°C

• Connection: M12 connector / 2m direct cable (optional)

• Probe Material: Stainless steel

• Housing Material: Stainless steel

• Weight: Approx. 0.4 kg

SN50/SN55 Series (Reference Specifications)

• Product Series: CATO SN50/SN55 series electronic flow switch

• Setting Range: Same as SN45 series (Water 1–150 cm/s, Oil 3–300 cm/s, Air 20–2000 cm/s)

• Signal Output: PNP / NPN / Relay (SPDT)

• Pressure Resistance: 100 bar

• Ingress Protection: IP67

• SN55 select models offer 4–20mA analog output

FS110 Series (Reference Specifications)

• Product Series: FS110 series flow switch (SN series derivative)

• Original Model: SN45-R14HDCRQ / SN45-G14HDCRQ

• Technical Parameters: Consistent with SN45 series

Key Technical Advantages

1. Thermal Principle – No Moving Parts, Maintenance-Free

The SN series operates on the thermal (calorimetric) principle with no moving parts inside the probe. Compared to mechanical flow switches (paddle-type, vane-type, etc.), thermal flow switches have no wear, no sticking risk, and require no maintenance over long-term use—significantly reducing the total lifecycle cost of equipment.

2. Gas/Liquid Dual-Use for Multiple Media

The SN series is suitable for both liquid and gas media flow monitoring—water (1–150 cm/s), oil (3–300 cm/s), and air (20–2000 cm/s). A single model covers hydraulic oil, cooling water, cutting fluids, lubrication oils, compressed air, and more.

3. Multiple Output Options for Flexible Control System Integration

The SN series offers PNP, NPN, and relay (SPDT N/O + N/C) signal outputs. PNP/NPN types support max. switching current of 400 mA; relay type supports max. 4 A. Whether connecting to PLC digital inputs or directly driving contactors and alarm lamps, flexible adaptation is ensured.

4. 6-LED Bar Display for Intuitive Status Indication

The SN series features a 6-LED bar display providing real-time visual indication of flow trend and switch status. Compared to plain flow switches without display, the LED bar display enables more intuitive on-site inspection and fault diagnosis.

5. Robust Construction for Harsh Industrial Environments

The SN series features all-stainless steel probe and housing, IP67 ingress protection, and pressure resistance up to 100 bar. Media temperature range -20°C to +80°C and ambient temperature range -20°C to +80°C. Suitable for demanding applications in cooling water, cutting fluids, lubrication oils, and hydraulic systems.

6. 100% Direct Interchangeability and Simulated Condition Testing

All models strictly adhere to CATO original mounting dimensions and interface standards (G1/4, G1/2 thread connections), enabling direct drop-in replacement of original flow switches without piping modification or system adjustment. Every unit undergoes 100% simulated operating condition bench testing prior to shipment, ensuring consistent, stable performance at rated pressure and temperature.

Application Areas

• Hydraulic Systems: Oil flow monitoring and pump dry-run protection for hydraulic power units and stations

• Cooling Water Systems: Flow monitoring and alarming for circulating water systems

• Cutting Fluid Systems: Cutting fluid flow monitoring for machine tools to prevent dry cutting damage

• Lubrication Systems: Flow monitoring and alarming for gearbox and bearing lubrication oils

• Pneumatic Systems: Flow monitoring for compressed air systems

• Pump Protection: Dry-run protection to prevent pump damage under no-flow conditions

Expert Maintenance Tips

1. Verify Model and System Compatibility Prior to Installation

The SN series offers multiple thread connections (G1/4, G1/2)and output types (PNP/NPN/Relay). Confirm prior to installation:

• Thread connection matches the piping (R14=G1/4; G12=G1/2; G14=G1/4)

• Output type matches the control system (PNP/NPN/Relay)

• Supply voltage matches the specification (24V DC or 230V AC)

2. Correct Installation Orientation

Thermal flow switches have specific installation orientation requirements. Ensure the probe is fully immersed in the medium and completely inserted into the pipe interior—avoid exposing the probe to air, which may cause false alarms. Install the switch in a section of pipe with stable medium flow, away from elbows, valves, and other turbulent areas.

3. Potentiometer Setting and Commissioning

The SN series uses a potentiometer to set the flow switching point. Rotate the potentiometer slowly while observing the 6-LED bar display for flow status changes. It is recommended to perform the setting at normal system operating flow to ensure accurate and reliable switching point configuration.

4. Electrical Connection Precautions

• PNP/NPN types: Max. switching current 400 mA—do not overload

• Relay type: Max. switching current 4 A—install appropriate overload protection in the contact circuit

• Connection options: M12 connector or 2m direct cable

• Power supply: 24V±20% DC or 230V±15% AC—verify power type and voltage match prior to wiring

5. Media Temperature and Cleanliness Management

The SN series media temperature range is -20°C to +80°C. Operating outside this range may result in reduced measurement accuracy or sensor damage. For applications with high solid particle content or high-viscosity media, install a filter upstream of the flow switch to prevent probe surface contamination from affecting measurement accuracy.

6. Periodic Functional Checks

Perform functional checks every 2,000 operating hours or annually: verify flow switching point accuracy, LED indication, and output signal reliability. If set-point drift or output anomalies are observed, arrange for servicing or replacement.