RCM Digital Flow Meter
Flowrate Indicator / Totalizer — Options RW3 & DR-1
The RCM Digital Flow Meter display is a microprocessor-driven instrument designed to display instantaneous flowrate, resettable total, and non-resettable accumulated total — all from a single 4–20 mA input signal.
Option RW3 is a self-contained 2-wire loop-powered transmitter and display in one unit. Option DR-1 connects as a remote display to any W, W2, W3, or RW3 transmitter output.
A scaled pulse output referenced to accumulated total is standard, enabling integration with PLCs, DCS systems, and remote totalizers.
Standard Features
- Microprocessor-driven — displays flowrate, total, and accumulated total
- 4–20 mA input (passive or active); powered by 24 Vdc external supply
- Large transflective LCD — seven 17 mm rate digits, eleven 8 mm total digits
- Scaled pulse output (max 500 Hz) referenced to accumulated total
- Linear or square root (DP) signal processing modes
- 15-point linearization of flow curve
- EEPROM backup — data retained during power failure (10-year minimum)
- Programmable engineering units for both rate and total simultaneously
- Low-flow cut-off (0.0–99.9%) to suppress leakage and signal noise
- Filter settings 01–99 for signal stability vs. response time
- 4-digit pass code protection for setup values
- Amber or green backlighting (optional, requires 24 Vdc)
- Rugged IP67 / NEMA 4X enclosure — indoor or outdoor use
System Description
Signal Input
4–20 mA flowmeter signal
Power
24 Vdc external (20–30 Vdc)
Pulse Output
Scaled to accumulated total
Safety & Installation Warnings
- Installation and servicing must be performed by authorized technicians.
- Disconnect power before opening housing.
- Never touch electronic components directly — ESD can permanently damage electronics.
- Grounding wire must never be removed on aluminum casing versions.
- Do not expose the system to conditions beyond enclosure ratings.
- Not intended for life support applications.
Control Panel Functions
- Enter SETUP mode (hold 7 sec)
- Save / confirm values
- Exit setup (hold 3 sec)
- Display accumulated total
- Increase values in setup mode
- Wake from shelf mode (press twice)
- Reset resettable total (press twice)
- Select digits during setup
Display Features
Setup Functions & Variables
- Units: L, m³, kg, lb, GAL, USGAL, bbl, or no units
- Decimal places: 0–3
- Span range: 0.000001 to 9,999,999 unit/sec
- Volume units: mL, L, m³, GAL, bbl, cf, scf, Nm³, NL, P
- Mass units: mg, g, kg, ton, lb
- Time base: sec, min, hour, day
- Mode: Total + Flowrate, or Flowrate only (large digits)
- Backlight: Off, Green, or Amber
- Brightness: Levels 1–5
- LCD refresh: Fast, 1 sec, 3 sec, 15 sec, 30 sec, or Off
- Battery mode: Operational or Shelf (extremely low power)
- Wake from shelf mode: press SELECT twice
Signal Processing
Interpolation Mode (Linear)
Linear relationship between input signal and flowrate. Use for velocity-type flow sensors.
Square Root Mode (DP)
Used for differential pressure applications. R = Flowrate, S = Span, I = Scaled analog input.
Filter Settings (01–99)
Higher filter values increase display stability but slow response time. Set based on your process dynamics.
| Filter Value | 50% Response | 90% Response |
|---|---|---|
| 02 | 0.3 sec | 1.0 sec |
| 10 | 1.8 sec | 5.6 sec |
| 50 | 8.8 sec | 29 sec |
| 99 | 17 sec | 57 sec |
Terminal Connections
4–20 mA signal from W2, W3, or RW3 transmitter
Passive transistor (NPN), max 500 Hz, 50 VDC / 300 mA
Required for amber or green backlighting
Calibration Procedure
Zero Calibration (4 mA)
- 1Connect multimeter in series with current loop.
- 2Pressurize the pipeline with no flow.
- 3Adjust zero potentiometer until output reads 4.00 mA ±0.02 mA.
Span Calibration (20 mA)
- 1Establish a known steady flow rate — as close to 95% full scale as practical.
- 2Set span using the formula below.
I = 16Q² + 4.00
I = mA output · Q = decimal % of full scale
All meters are factory calibrated. Span adjustment requires proper test equipment and the ability to establish a known steady flow rate close to full scale. Adjustment of the span WILL affect meter calibration.
% Full Scale to Current Output
| % Full Scale | Current Output (mA) |
|---|---|
| 20% | 4.64 |
| 30% | 5.44 |
| 40% | 6.56 |
| 50% | 8.00 |
| 60% | 9.76 |
| 70% | 11.84 |
| 80% | 14.24 |
| 90% | 16.96 |
| 95% | 18.44 |
| 100% | 20.00 |
Output is non-linear (quadratic) — linearize in receiving device.
Pulse Output
Output Type
Passive transistor (NPN), non-isolated
Max Frequency
500 Hz
Max Load
50 VDC / 300 mA
Pulse Width
0.001–9.999 sec (programmable)
Terminals
7 (–) and 8 (+)
Trigger
Every X accumulated quantity units
Enclosure & Installation
NEMA 4X / IP67 Enclosure
- Indoor or outdoor use, including offshore applications
- Protection against windblown dust and rain
- Protection from splashing and hose-directed water
- Corrosion-resistant construction
- IP67: dust-tight and water-tight up to 1 m immersion
Installation Requirements
- 10 pipe diameters of straight pipe upstream — no special downstream requirements.
- Meters calibrated based on Schedule 40 pipe ID — tubing or hose may affect accuracy.
- Avoid water hammer, extreme temperature changes, condensation, and excess vibration.
- Protect system from freezing liquids.
Maintenance & Repair
Periodic Checks
- Housing condition
- Cable glands
- Wiring integrity
- Calibration accuracy
- Battery condition
Repair Policy
- Product is not user repairable.
- Obtain an RMA number before returning any unit.
Full Wiring & Calibration Reference
Detailed connection diagrams, loop impedance chart, and step-by-step calibration for W2 & W3 transmitters.
Digital Flow Meter FAQ
Common questions about the RW3 transmitter/display and DR-1 remote display — wiring, programming, and troubleshooting.
Understanding the Digital Meter
Signal & Wiring
Setup & Programming
Enclosure & Maintenance
Have a question about the digital meter not covered here?
Our engineering team is available Mon–Fri, 8:30am–4:30pm EST.
Typical Applications
Building Automation
Chilled water and hot water flow with BAS integration via 4–20 mA
Process Control
Closed-loop flow control where a signal output is required by a PLC or DCS
Energy Management
Sub-metering compressed air or water consumption with totalizer
Laboratories
Precise flow rate display and logging for research applications
OEM Equipment
Embedded in skid-mounted systems requiring digital flow indication
Utilities
Remote monitoring of flow rates in unmanned pump stations
Specifications
| Specification | Standard |
|---|---|
| Accuracy | ±3% F.S. |
| Repeatability | ±1% F.S. |
| Pressure Max. | 180 psig (12.6 kg/cm²) |
| Pressure Min. | 10 psig (0.67 kg/cm²) |
| Temperature Max. | 212°F (100°C) |
| Temperature Min. | -30°F (-34°C) |
| Enclosure Rating | IP67 / NEMA 4X |
| Power Supply | 20–30 Vdc (24 Vdc nominal) |
| Power Consumption | Max 1 Watt |
| Signal Input | 4–20 mA DC (passive or active) |
| Rate Display | Seven 17 mm (0.67″) digits — high intensity LCD |
| Total Display | Eleven 8 mm digits |
| Operating Temperature | -40°C to +80°C (-40°F to +178°F) |
| Humidity | 0–90% Non-condensing |
| Pulse Output | Passive transistor (NPN), max 500 Hz, 50 VDC / 300 mA |
| Pulse Width | 0.001–9.999 sec (programmable) |
| Data Protection | EEPROM backup — 10-year minimum retention |