SMC PF3W704S-N03-AT-G Digital Flow Switch for Water with Flow Adjustment Valve, 0.5–4 L/min, 3/8" NPT, Dual NPN, Temperature Sensor, gal/min Display, IP65
SMC
$460.00
The SMC PF3W704S-N03-AT-G is a 3-color digital flow switch for water with a rated flow range of 0.5 to 4 L/min, an integrated flow adjustment valve for manual setpoint trim, 3/8" NPT female ports, dual NPN switch outputs (OUT1 + OUT2), an integrated temperature sensor, M8 connector lead wire (3 m), and a US-customary display in gal/min. Built for closed-loop chiller lines, mold-cooling circuits, weld-tip cooling, and laser cooling-water monitoring where flow needs to be both dialed in and supervised from a single device.
Key Features
- Integrated flow adjustment valve. Built-in needle valve lets you set the cooling flow rate at install without adding a separate inline valve — reduces fitting count and leak paths.
- Dual NPN switch outputs. OUT1 and OUT2 are both NPN open-collector switch outputs. OUT2 can be assigned by the user to drive on flow rate OR fluid temperature — one device, two independent trip points.
- Integrated temperature sensor. Monitor fluid temperature alongside flow, with switching on a 0–100°C rated range (display –10 to 110°C, ±2°C accuracy).
- US-customary display (gal/min). The "G" unit code shows instantaneous flow in gal/min and accumulated flow in gal, with temperature in °C — matches US shop-floor conventions and chiller specs.
- 3-color, 2-screen rotatable display. Main screen shows instantaneous flow in red or green for at-a-glance status; white sub-screen displays set value, accumulated flow, peak/bottom, line name, or temperature. Display rotates 90° CCW / 225° CW in 45° increments.
- Compact PF3W7 body. Approximately 40% smaller than the legacy PF2W704 it replaces, with shorter required upstream straight-pipe runs.
- Karman vortex detection. No moving parts in the primary flow path — no impeller wear, no paddle fouling.
- Non-grease wetted parts. PPS body and sensor, SCS13 stainless attachment, SS304 temperature sensor, FKM seal — suitable for water and ethylene glycol aqueous solutions (viscosity ≤ 3 mPa·s).
- IP65 enclosure with C-UL-US listing, CE marking, and RoHS compliance.
PF3W704S-N03-AT-G Part Number Breakdown
Each segment of the SMC PF3W7 part number specifies a configuration option. Here is exactly what you receive when you order PF3W704S-N03-AT-G:
| Code Segment | Meaning |
|---|---|
| PF3W7 | PF3W7 series, integrated display, 3-color digital flow switch for water |
| 04 | Rated flow range 0.5 to 4 L/min (approx. 0.13 to 1.06 gal/min) |
| S | With integrated flow adjustment valve (needle-valve setpoint trim) |
| N | NPT thread type |
| 03 | 3/8" piping port size |
| A | OUT1: NPN open collector switch | OUT2: NPN open collector switch (assignable to flow or temperature) |
| T | With integrated temperature sensor |
| (no code) | Lead wire with M8 connector (3 m) included — default |
| G | Display units: gal/min flow, gal accumulated, °C temperature |
| (no R) | No mounting bracket (direct-mount or panel-mount only) |
Specifications
| Series | PF3W7, integrated display, with flow adjustment valve |
| Applicable fluid | Water, ethylene glycol aqueous solution (viscosity ≤ 3 mPa·s / 3 cP) |
| Detection method | Karman vortex |
| Rated flow range | 0.5 to 4 L/min (approx. 0.13 to 1.06 gal/min) |
| Display flow range | 0.35 to 5.50 L/min (below 0.35 L/min shown as 0.00) |
| Set flow range | 0.35 to 5.50 L/min |
| Smallest settable increment | 0.01 L/min |
| Display units | Instantaneous flow: gal/min | Accumulated flow: gal | Temperature: °C |
| Accuracy | ±3% F.S. (display) |
| Repeatability | ±2% F.S. |
| Temperature characteristics | ±5% F.S. (25°C standard) |
| Fluid temperature range | 0 to 90°C (no freezing or condensation) |
| Operating pressure range | 0 to 1 MPa (0 to approx. 145 psi) — derates at higher fluid temperature |
| Proof pressure | 1.5 MPa |
| Pressure loss | 45 kPa or less at maximum flow (varies with valve setting) |
| Switch output (OUT1) | NPN open collector, max load 80 mA, max applied voltage 28 VDC, internal voltage drop ≤ 1 V at 80 mA |
| Switch output (OUT2) | NPN open collector, same electrical specs as OUT1 (assignable: flow rate or temperature) |
| Response time (switch) | Selectable 0.5 s / 1 s / 2 s |
| Output modes (flow) | Hysteresis, window comparator, accumulated output, or accumulated pulse output |
| Output modes (temperature) | Hysteresis or window comparator |
| Temperature sensor rated range | 0 to 100°C (display –10 to 110°C, 1°C increment, ±2°C display accuracy) |
| Flow adjustment valve | Integrated needle-type for setpoint trim — intended for one-time install adjustment, not continuous modulation |
| Display | 2-screen: main 4-digit 7-segment red/green, sub 6-digit 11-segment white; 5 updates/second; rotatable 90° CCW / 225° CW in 45° steps |
| Power supply | 12 to 24 VDC ±10%, 50 mA or less |
| Piping port | 3/8" NPT female |
| Connection | M8 connector, 4-wire, 3 m lead wire included |
| Wetted parts | PPS (body, sensor, valve body, valve cover, shaft support), SCS13 (attachment), SS304 (temperature sensor body and shaft, valve shaft), FKM (seals) — non-grease |
| Enclosure rating | IP65 |
| Operating temperature | 0 to 50°C (no freezing or condensation), 35 to 85% RH |
| Standards / compliance | C-UL-US listed, CE marking (EMC, RoHS directives) |
| Weight | Approx. 470 g (sensor with temp sensor & flow adjustment valve + 3 m lead wire) |
| Wiring | Brown = DC (+), Black = OUT1, White = OUT2, Blue = DC (–) |
M8 Connector Pin Assignment
| Pin | Signal | Wire Color |
|---|---|---|
| 1 | DC (+) | Brown |
| 2 | OUT2 (NPN switch, assignable: flow or temperature) | White |
| 3 | DC (–) | Blue |
| 4 | OUT1 (NPN switch, flow rate) | Black |
Typical Applications
- Chiller and cooling-water loops — dial in the per-line coolant flow at install with the built-in valve, then trip OUT1 on low flow and OUT2 on over-temperature without adding hardware.
- Multi-zone mold cooling — balance flow across mold zones from the device itself, with independent NPN trips back to the PLC for each zone’s health.
- Resistance welding tip cooling — verify weld-gun cooling and detect blockages before tip damage occurs, with the integrated valve set during commissioning.
- Industrial laser and plasma cooling — supervise small-bore coolant lines (3/8") where flow rates fall in the 0.5–4 L/min window and per-head trim is required.
- Vacuum pump and spindle cooling — combined low-flow and over-temperature interlock back to the machine controller.
- US-shop installations — gal/min display matches the units already on chiller nameplates, pump curves, and machine specs in North American facilities.
What’s Included
- PF3W704S-N03-AT-G digital flow switch with integrated temperature sensor and flow adjustment valve
- Lead wire with M8 connector, 3 m (ZS-40-A)
Mounting bracket is not included with this configuration. Order ZS-40-K separately if a bracket is required — note that units with flow adjustment valve require 2 brackets per device.
Compatible Accessories
- ZS-40-K — mounting bracket with 4 tapping screws (PF3W704/720 size). Two brackets required when the flow adjustment valve is present.
- ZS-40-A — replacement lead wire with M8 connector (3 m)
Frequently Asked Questions
What does the "S" in PF3W704S-N03-AT-G mean?
The S in the part number designates the variant with the integrated flow adjustment valve — a built-in needle-type valve that lets you set the flow rate at install without adding a separate inline valve. The non-S variant (PF3W704-N03-AT-G) is the same switch without the integrated valve.
Can I use the flow adjustment valve to modulate flow during operation?
No. SMC specifies the integrated flow adjustment valve for one-time setpoint trim at install, not for continuous or frequent adjustment. Repeated cycling of the valve can wear the internal seal and lead to leakage. For applications requiring active flow modulation, pair a non-S PF3W7 switch with a dedicated SMC flow controller such as the FC2W.
What is the output configuration?
The A code designates both OUT1 and OUT2 as NPN open-collector switch outputs. OUT1 is driven by flow rate. OUT2 can be assigned by the user to drive on either flow rate or fluid temperature, giving you two independent NPN trips from one device. There is no analog output on this variant — for 1–5V analog use the "C" or "E" output codes; for 4–20 mA use the "D" or "F" codes.
Why does the display show gal/min instead of L/min?
The G unit code at the end of the part number sets the display to US gallons per minute for instantaneous flow and US gallons for accumulated flow, with temperature in °C. This matches the unit conventions on most North American chillers and machine specs. SMC also offers M (L/min, L, °C), F (gal/min, gal, °F), and J (L/min, L, °F) unit variants.
What fluids can the PF3W704S measure?
Water and ethylene glycol aqueous solutions with viscosity of 3 mPa·s (3 cP) or less. The standard FKM seal and PPS/SS304/SCS13 wetted parts are suitable for most cooling-water and glycol-cooled circuits. For deionized water and chemical liquids, SMC offers the PF3W-U variants with CPVC piping.
How accurate is the PF3W704S?
Display accuracy is ±3% of full scale, with ±2% F.S. repeatability. Temperature display accuracy is ±2°C. Achieving rated accuracy requires at least 8 cm of straight pipe upstream of the inlet port at 4 L/min on the 3/8" size.
What is the maximum operating pressure?
Rated operating pressure is 0 to 1 MPa (~145 psi) and proof pressure is 1.5 MPa. Note that pressure rating derates at higher fluid temperatures and that units with the flow adjustment valve have a slightly different derating curve than non-valve variants — refer to the SMC PF3W catalog for the pressure-vs-temperature chart for the "S" variants.
Does this unit include a mounting bracket?
No. The absence of the R code at the end of the part number indicates no bracket. If you need a bracket, order ZS-40-K separately — and note that units with the flow adjustment valve require two brackets per device because of the longer body length.
What’s the difference between PF3W704S-N03-AT-G and the older PF2W704?
The PF3W7 series is the current generation. It is approximately 40% smaller than the legacy PF2W704, has a shorter required upstream straight-pipe length, adds a 3-color/2-screen rotatable display, and integrates the temperature sensor and flow adjustment valve as native options. PF3W7 is the recommended replacement for new builds and PF2W704 retrofits.
Need help configuring the right SMC PF3W flow switch?
Automation Distribution is an authorized SMC distributor with engineering support on water flow switches, chillers, and fluid process products. Call 1-888-600-3080 or contact us for application sizing, cross-references, and stock checks on the full PF3W7 family.
- Type:
- Integrated Display
- Rated Flow Range (Flow Range):
- 0.5 To 4 L/min
- Flow Adjustment Valve:
- Yes
- Thread Type:
- NPT
- Port Size:
- 3/8
- Output Specification/Temperature Sensor:
- OUT1 Flow Rate:NPN
- Lead Wire/Option:
- With Lead Wire With M8 Connector (3 m)
- Remote Sensor Unit:
- Instantaneous Flow Rate:gal/min
- Bracket:
- Without Bracket
- Calibration Certificate (Only Flow Sensor):
- None
- Made To Order:
- Standard
