Signet Flow Meter: Georg Fischer Paddlewheel Sensor Specs

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Signet Flow Meter: Georg Fischer Paddlewheel Sensor Specs

Quick Answer

Georg Fischer Signet paddlewheel flow sensors deliver ±0.5% of reading accuracy on clean, low-viscosity fluids. They work across pipe sizes from DN15 to DN900 with insertion and inline styles. Output options include open-collector NPN, 4-20 mA, and S³L digital. Typical applications span RO/DI water skids, cooling tower loops, chemical dosing, and batch transfers. Silver Automation Instruments stocks Signet 2536, 2537, 2540, and 8512 sensors for fast shipment to Vietnam, Indonesia, Mexico, Nigeria, and UAE.

What the Georg Fischer Signet Paddlewheel Sensor Is

The Signet paddlewheel sensor measures liquid flow by counting turbine revolutions with an infrared photoelectric or Hall effect pickup. A low-inertia rotor spins freely on a ceramic or sapphire shaft, generating a frequency signal proportional to velocity. Because there are no magnetic couplings or mechanical drag from a gear train, the sensor starts reliably at velocities as low as 0.3 m/s. Most engineers select this design for clean water, RO permeate, light chemicals, and clear coolant lines. The housing material options are PP (polypropylene), PVDF, or 316L stainless steel, and the rotor and shaft come in PVDF, ETFE, or ceramic. For seawater and brackish water monitoring, we specify the PP body with ceramic shaft because galvanic corrosion on metal parts causes early failure on customer sites in Southeast Asia.

Core Specifications That Matter in Practice

Pipe diameter range: DN15 to DN900. The wafer-style 2536 fits DN15–DN50 directly between flanges. The insertion series 2540 and 8512 work in pipes from DN50 up to DN900 through a 1.5-inch NPT or ISO weld-on fitting. Flow velocity range: 0.3 to 6 m/s. Below 0.3 m/s the rotor stutters and you lose linearity. Above 6 m/s bearing wear accelerates. Temperature rating: PP bodies 80°C at 6.9 bar, PVDF bodies 100°C at 10 bar, 316L bodies 120°C at 25 bar. Ambient electronics: 70°C with standard pick-up. Turndown ratio is practically 20:1 on water, but with viscous fluids above 10 cP you must re-calibrate. Output configuration: the base sensor gives a raw 0-5 VDC pulse, which you feed into a Signet 8550, 9900, or 9950 transmitter. The transmitter converts it to 4-20 mA, relay, or digital S³L bus. Many customers in the Middle East connect the open-collector output directly to a PLC with a 10 kΩ pull-up resistor and skip the transmitter entirely.

Model Selection Guide

2536 Wafer Sensor (DN15–DN50). Inline mount, PVDF body, sapphire bearings, ETFE rotor. Best for ultra-pure water, pharmaceutical WFI loops, and small RO lines. Accuracy ±0.5% of reading after field K-factor correction. Pressure drop at 5 m/s is about 0.1 bar on DN50.

2537 Rotor-X (DN20–DN50). Threaded NPT or BSP process connection, 316L or PVDF body, ceramic shaft. This one handles light oils, glycol, and coolant up to 10 cP without signal loss. We sell many 2537 units to food processors in Thailand for pasteurizer water balance tracking.

2540 Insertion Sensor (DN50–DN900). PVDF or 316L, wet-tap or weld-on fitting, Hall effect element. Depth adjustment is 0.5 inch increments, locked by a compression ferrule. In large chilled water pipes of 600 mm, one sensor at the top-dead-center position gives repeatable velocity reading if you have 20D straight run upstream.

8512 Metallic Insertion (DN50–DN900). All 316L body, ceramic bearings, rated 200°C with remote amplifier. Used on boiler feedwater, hot condensate return, and steam condensate. Last year a customer in Nigeria put four 8512 sensors on a 300 mm condensate header at 180°C and 16 bar. They needed the remote preamplifier because the pipe vibration was too high for integral electronics.

Installation Notes Engineers Skip

Straight pipe requirement is 10 diameters upstream and 5 downstream for ±1% erro

Transmitter and Output Pairing

The raw sensor needs a transmitter unless your PLC can read frequency directly. Signet 8550 is a basic panel meter with 4-20 mA output and two relays, IP65 front, 12-24 VDC powered. Signet 9900 is the multi-parameter version and accepts flow, pH, ORP, conductivity, and pressure modules. Signet 9950 adds dual channel, USB data logging, and Modbus RTU. We recommend the 9900 for most water treatment panels because you can add a pH sensor later without changing the panel cutout. All transmitters accept K-factors from 0.01 to 99999.9 pulses per litre. The factory K-factor engraved on the sensor cap is a starting point; you must perform a bucket test or compare against a clamp-on ultrasonic for better than 1% totalized volume accuracy.

FAQ

Can the Signet paddlewheel measure viscous fluids over 10 cP? Above 10 cP the velocity profile changes from turbulent to transitional, and the K-factor shifts non-linearly. You can create a custom K-factor curve in the 9900 transmitter with up to 16 points, but repeatability will degrade. For oils above 50 cP, switch to an oval gear or Coriolis meter.

What is the difference between the 2536 and 2537? The 2536 is a wafer-style inline sensor for DN15-DN50 with PVDF body only. The 2537 is a threaded inline sensor with either PVDF or 316L body. The 2537 accepts higher pressure at temperature and the metal body option makes it suitable for glycol and light fuels.

Do I need the Signet transmitter or can I connect directly to PLC? The sensor outputs a frequency pulse (0-5 VDC NPN open collector). If your PLC has a high-speed counter input with a 5V or 10V pull-up, you can wire it directly. Most Siemens S7-1200 and Mitsubishi FX5U PLCs handle this without extra modules. The transmitter is useful when you need local display, 4-20 mA for a SCADA, or relay outputs for batch control.

How often does the rotor need replacement? On clean water at 2 m/s, the rotor lasts 3–5 years. Abrasive particles like sand or iron oxide will wear the bearing in 6–12 months. A paint manufacturer in Indonesia found that TiO2 pigment in rinse water caused rotor failure every 8 months; they solved it by adding a 50-micron Y-strainer upstream.

Can I use it for seawater or brine? Yes with careful material selection. Use the PP body, ceramic shaft, and titanium retaining clip option. The standard 316L clip pits within weeks in warm seawater. We ship this configuration to desalination plants in Saudi Arabia and Oman regularly. Silver Automation Instruments stocks the 3-2536-PP-CER-TI assembly for this exact application.

Why Get It from Silver Automation Instruments

We keep GF Signet sensors, transmitters, and fittings in stock at our Nanjing warehouse and ship DHL Express to Jakarta, Bangkok, Lagos, Dubai, and Mexico City within 3 working days. Our engineers have configured over 200 Signet loops for wastewater, HVAC, and chemical batching. Send us your fluid type, pipe diameter (DN), flow range (m³/h), temperature (°C), and output requirement. We will reply within 4 hours with a datasheet, K-factor validation, and a landed-cost quotation.

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