SMC PF3W704-N03-ET-MR Digital Flow Switch for Water, 0.5–4 L/min, 3/8" NPT, PNP + 1–5V Analog, Temperature Sensor, 3-Color Display, IP65
SMC
$700.60
The SMC PF3W704-N03-ET-MR is a 3-color digital flow switch for water with a rated flow range of 0.5 to 4 L/min, 3/8" NPT female ports, PNP switch output on OUT1, 1–5V analog output on OUT2, an integrated temperature sensor, M8 connector lead wire (3 m), and mounting bracket. Built for closed-loop chiller lines, weld-tip cooling, mold-cooling circuits, and laser cooling-water monitoring where flow rate and fluid temperature both need to be supervised from a single device.
Key Features
- Flow and temperature on one device. OUT1 is a PNP switch output driven by flow rate; OUT2 is a 1–5V analog output that can be assigned to either flow rate or fluid temperature.
- 3-color, 2-screen display. Main screen shows instantaneous flow in red or green for at-a-glance status; the white sub-screen displays the set value, accumulated flow, peak/bottom, line name, or temperature.
- Rotatable display. Rotates 90° counterclockwise and 225° clockwise in 45° increments — readable in nearly any installation orientation.
- Compact PF3W7 body. Roughly 40% smaller than the legacy PF2W704 it replaces, with shorter required upstream straight-pipe runs — saves panel and skid space.
- Karman vortex detection. No moving parts in the flow path — no impeller wear, no orifice plugs, no paddle to foul.
- 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.
- Mounting bracket and 3 m M8 lead wire included.
PF3W704-N03-ET-MR Part Number Breakdown
Each segment of the SMC PF3W7 part number specifies a configuration option. Here is exactly what you receive when you order PF3W704-N03-ET-MR:
| 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 |
| (no S) | No flow adjustment valve |
| N | NPT thread type |
| 03 | 3/8" piping port size |
| E | OUT1: PNP open collector (flow switch) | OUT2: Analog voltage 1–5V |
| T | With integrated temperature sensor |
| M | Lead wire with M8 connector (3 m) | Display units: L/min, L, °C |
| R | With mounting bracket (ZS-40-K, includes 4 tapping screws) |
Specifications
| Series | PF3W7, integrated display |
| 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 |
| Accuracy | ±3% F.S. (display and analog output) |
| 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) |
| Proof pressure | 1.5 MPa |
| Pressure loss | 45 kPa or less at maximum flow |
| Switch output (OUT1) | PNP open collector, max load 80 mA, max applied voltage 28 VDC, internal voltage drop ≤ 1.5 V at 80 mA |
| Analog output (OUT2) | 1 to 5 V, output impedance 1 kΩ (selectable: flow rate or temperature) |
| Response time (switch) | Selectable 0.5 s / 1 s / 2 s |
| Output mode (flow) | Hysteresis, window comparator, accumulated output, or accumulated pulse output |
| Output mode (temperature) | Hysteresis or window comparator |
| Temperature sensor rated range | 0 to 100°C (display range –10 to 110°C, 1°C increment, ±2°C display accuracy) |
| Temperature analog accuracy | ±3% F.S., 7 s response time |
| 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), SCS13 (attachment), SS304 (temperature sensor body and shaft), FKM (seal) — 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. 370 g (sensor with temperature sensor + 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 (1–5V analog: flow or temperature) | White |
| 3 | DC (–) | Blue |
| 4 | OUT1 (PNP switch, flow rate) | Black |
Typical Applications
- Chiller and cooling-water loops — monitor circulating coolant flow and supply/return temperature on the same device, and trip the PNP switch if flow drops below a setpoint.
- Resistance welding tip cooling — verify cooling water is reaching weld guns and detect blockages before tip damage occurs.
- Injection mold cooling circuits — confirm flow through individual mold zones, with the 1–5V analog output trended in the PLC for cycle-by-cycle process verification.
- Industrial laser and plasma cooling — supervise small-bore coolant lines (3/8") where flow rates fall in the 0.5–4 L/min window.
- Vacuum pump and spindle cooling — flag low-flow or over-temperature conditions before component damage.
- Ethylene glycol coolant systems — rated for glycol/water mixtures up to 3 mPa·s viscosity.
What’s Included
- PF3W704-N03-ET-MR digital flow switch with integrated temperature sensor
- Lead wire with M8 connector, 3 m (ZS-40-A)
- Mounting bracket with 4 tapping screws (ZS-40-K)
Compatible Accessories
- ZS-40-A — replacement lead wire with M8 connector (3 m)
- ZS-40-K — replacement bracket (with 4 tapping screws) for PF3W704/720
Frequently Asked Questions
What is the output configuration of the PF3W704-N03-ET-MR?
The "E" code in PF3W704-N03-ET-MR designates OUT1 as a PNP open-collector switch output (driven by flow rate) and OUT2 as a 1–5V analog output. The analog output can be assigned by the user to either flow rate or fluid temperature. The "T" code adds the integrated temperature sensor.
What fluids can the PF3W704 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 PF3W704?
Display and analog output accuracy is ±3% of full scale, with ±2% F.S. repeatability. Temperature display accuracy is ±2°C and temperature analog output accuracy is ±3% F.S. 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. The pressure rating derates at higher fluid temperatures — refer to the SMC PF3W catalog for the pressure-vs-temperature curve.
What is the difference between PF3W704 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 option natively. PF3W7 is the recommended replacement for new builds and PF2W704 retrofits.
Does the PF3W704-N03-ET-MR have a flow adjustment valve?
No. The absence of the "S" code in the part number indicates no integrated flow adjustment valve. If you need an integrated needle valve to dial in the flow rate, order the PF3W704S-N03-ET-MR variant. Note that SMC’s flow adjustment valve is not designed for continuous re-adjustment — it is intended for one-time setpoint trim.
Is this product compatible with PLCs that accept 4–20 mA?
No, the "E" output code on this part number provides a 1–5V voltage output, not 4–20 mA. If you require a current loop, the corresponding 4–20 mA variant uses the "F" code — reach out to Automation Distribution for the right configuration.
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.
