GF Signet 2551 Magmeter Flow Sensor

Insertion magmeter for conductive liquids in DN15…DN900 (½…36 in.) pipe when you need frequency, digital S3L, or 4–20 mA flow with optional local display and totalizers.

Key advantages

Wide pipe ladder — DN15…DN900 (½…36 in.); operating velocity 0.05…10 m/s (0.15…33 ft/s).
±1% of reading + 0.1% FS — linearity; 4–20 mA loop error 32 μA max @ 25 °C / 24 VDC.
Multiple outputs — frequency, digital S3L, 4–20 mA; relays on display versions.
No moving parts — empty-pipe detection; bi-directional frequency; uni- or bi-directional 4–20 mA.

Typical applications

Chemical processing, water/wastewater, HVAC, irrigation, and scrubber control on conductive liquids.
Lines using GF Signet installation fittings where alignment and insertion depth are automatic.
Wet-tap installs when the sensor must be removable under process pressure.

Selection guide

Pipe size / velocity — Operating velocity 0.05…10 m/s; pipe sizes DN15…DN900. Match fitting size to the line.
Accuracy — Linearity ±1% of reading plus 0.1% of full scale; repeatability ±0.5% of reading @ 25 °C.
Minimum conductivity — 20 μS/cm. Confirm media conductivity before RFQ.
Output — Frequency; digital S3L; 4–20 mA; relays on display versions. Blind versions available.
Supply — 4–20 mA: 24 VDC ±10%, 22.1 mA max; Frequency: 5–24 VDC ±10%, 15 mA max; S3L: 5–6.5 VDC, 15 mA max; relays aux 9–24 VDC, 0.4 A max.
Process connection — GF Signet installation fittings; wet-tap options available.
Wetted materials — PP/316L SS; PVDF/Titanium; PVDF/Hastelloy-C; O-rings FKM (std), EPDM/FFKM optional.
Pressure / media temp — Max pressure PP 10.3 bar @ 25 °C / 1.4 bar @ 85 °C; media temperature 0…85 °C.
Housing / IP — Case PBT; NEMA 4X / IP65 with cap installed.

Common mistakes

Ordering into media below 20 μS/cm — published minimum conductivity is a hard limit.
Ignoring the PP pressure derate at elevated temperature.
Specifying PP/316L SS when chemistry needs PVDF/Titanium or PVDF/Hastelloy-C.
Mixing S3L host expectations (GF 9900/9950) with a bare 4–20 mA PLC loop without confirming the output code.
Assuming relays are always present — relays ship on display versions only.
Flow instruments · Flow buying guide

When to RFQ / what to tell us

Pipe size (DN15…DN900), fluid conductivity, and working velocity / flow.
Output needed: frequency, S3L, 4–20 mA; display vs blind; relays yes/no.
Wetted material set and O-ring (FKM / EPDM / FFKM).
Process temperature and pressure (check PP derate), wet-tap yes/no.
Host instrument (9900/9950 / 0486 / PLC), quantity, ship-to country.

Request a Quote · Get selection help

Specs

Spec	Value
SKU	20200
Brand	Georg Fischer / GF Signet
Model	2551
Product type	magmeter
Measuring range	Operating velocity 0.05 to 10 m/s (0.15 to 33 ft/s); pipe sizes DN15 to DN900 (½ to 36 in.)
Accuracy	Linearity ±1% of reading plus 0.1% of full scale; 4–20 mA loop accuracy 32 μA max error (25 °C @ 24 VDC)
Repeatability	±0.5% of reading @ 25 °C (77 °F)
Output signal	Frequency; digital S3L; 4–20 mA; relays on display versions
Supply voltage	4–20 mA: 24 VDC ±10% 22.1 mA max; Frequency: 5–24 VDC ±10% 15 mA max; S3L: 5–6.5 VDC 15 mA max
Process connection	GF Signet installation fittings; wet-tap options available
Wetted materials	PP/316L SS; PVDF/Titanium; PVDF/Hastelloy-C; O-rings FKM (std), EPDM/FFKM optional
Housing material	Case PBT; display window polyamide; retaining nuts PP/PVDF (Valox optional)
IP rating	NEMA 4X / IP65 (with cap installed)
Media temperature	0 to 85 °C (32 to 185 °F)
Ambient temperature	Operating −10 to 70 °C; storage −20 to 70 °C
Display	Optional multi-language display with totalizers/relays (blind versions available)
Communication	Digital S3L; compatible with GF 9900/9950 and 0486 Profibus concentrator
Approvals	CE; FCC; UL; CUL; NSF (3-2551-PX-XX); FM Measuring Equipment 77CJ; RoHS
Weight	0.680 kg (1.50 lb) shipping
Notes	Minimum conductivity 20 μS/cm. Max pressure PP 10.3 bar @ 25 °C / 1.4 bar @ 85 °C. Values aligned with GF documentation 3-2551.099 Rev M 06/2026-A.

Documents

GF Signet 2551 datasheet (PDF)

FAQ

Q: Will the 2551 work on low-conductivity water? A: Published minimum is 20 μS/cm. Below that, pick another technology or confirm the fluid with us before RFQ.

Q: Frequency, S3L, or 4–20 mA — which output do I need? A: Frequency or 4–20 mA for PLC/analogue loops; S3L when the host is a GF Signet instrument (9900/9950) or 0486. Output is ordered by model code.

Q: Do I always get a display and relays? A: No. Display with totalizers/relays is optional; blind versions are available. State display and relay needs in the RFQ.

Q: What should I send for a quote? A: Pipe size, conductivity, velocity/flow, output and display choice, wetted materials, T/P, wet-tap yes/no, quantity. Compatible with systems using GF Signet 2551 if you need a drop-in check — we do not claim authorized-dealer status.