Industrial Water Quality PHEC Sensor Transmitter Standard 1.0 5-in-1 with Display RS485 4-20mA

Specifications

• Operating Voltage: 12V–24V DC
• Communication Interface: RS485 (Modbus) + 2× independent 4-20mA analog current loop outputs
• Display: Integrated LCD with backlight
• Measured Parameters (5-in-1): pH, ORP, EC, TDS, Salinity
• pH: Resolution 0.01, Range 0–14, Accuracy ±0.05
• EC: Resolution 1 µS/cm, Accuracy ±2% (this unit's probe rated 0–2000 µS/cm)
• TDS: Resolution 1 ppm, Range 0–1000 ppm, Accuracy ±2%
• Temperature: Resolution 0.1°C, Range 0–60°C, Accuracy ±0.5°C
• Salinity: Resolution 0.01%, Range 0–25%, Accuracy ±0.1%
• Sensor Inputs: BNC connector (pH/ORP combination electrode), 4-terminal connector for EC probe (Ta/Tb temp. compensation + C+/C- conductivity)
• Included Probes: 1× pH/ORP combination electrode (BNC, long cable), 1× EC probe (model EC1.0, PG7 waterproof cable gland)
• Mounting: DIN-rail style transmitter housing

Minimum hardware

• 12V or 24V DC regulated power supply : the transmitter is rated for 12-24V DC input; using an unregulated or under-rated supply can cause unstable readings or intermittent resets under load
  
• RS485-to-USB converter : needed if you plan to read Modbus data on a PC or single-board computer rather than a dedicated PLC
  
• PLC or microcontroller with RS485/Modbus support :required to actually capture and log the transmitter's output; a bare Arduino Uno needs an added RS485 module (e.g., MAX485) to read this device
  
• Screwdriver : for wiring into the terminal block's screw terminals
  

Safety Warnings

• Voltage Warning: This transmitter operates at 12–24V DC, NOT 5V or 3.3V logic level do not connect VCC directly to an Arduino or ESP32's 5V/3.3V pin, as this is a separate power domain
  
• Polarity Warning: Reversing VCC and GND on the power input can damage the transmitter's internal circuitry — always double-check polarity before powering on
  
• ESD Warning: Handle the pH/ORP glass electrode tip with care : physical shock or static discharge near the sensing bulb can permanently damage it
  
• Probe Storage Warning: Never let the pH/ORP electrode tip dry out for extended periods — dried reference junctions cause drift and inaccurate readings

Accessories Included in the Box

• 1× PHEC 1.0 Transmitter Unit (with LCD display)
• 1× pH/ORP Combination Electrode (BNC connector, long cable)
• 1× EC Probe (model EC1.0, PG7 waterproof cable gland, long cable)

Frequently Asked Questions

• Is the PHEC 1.0 compatible with a standard PLC?
  Yes, it outputs both RS485 Modbus and 4-20mA current loop signals, which are the two most common industrial input types supported by nearly all PLCs.
• Can I connect the PHEC 1.0 to an Arduino or Raspberry Pi?
  Yes, but you'll need an RS485 module such as the MAX485 for Arduino, or a USB-to-RS485 converter for Raspberry Pi, since neither board has native RS485 hardware.
• Does the PHEC 1.0 work with SCADA software?
  Yes, since it communicates over standard Modbus RTU protocol via RS485, it is compatible with most SCADA systems that support Modbus device integration.
• Can I use both the RS485 output and the 4-20mA output at the same time?
  Yes, the transmitter provides independent RS485 and dual 4-20mA outputs simultaneously, so you can log full data digitally while also feeding a simple analog value to a separate controller.
• What voltage does the PHEC 1.0 require?
  It requires a 12V to 24V DC power supply — it will not operate on standard 5V USB power like typical hobbyist sensor modules.
• Can I power the PHEC 1.0 from a 5V source?
  No, 5V is below the transmitter's minimum rated input of 12V DC and will prevent it from powering on correctly.
• What happens if I reverse the VCC and GND wiring?
  Reversed polarity on the power input can damage the transmitter's internal circuitry, so always verify polarity with a multimeter before first power-on.
• How do I wire the PHEC 1.0 for RS485 communication?
  Connect the A and B terminals to your RS485 converter or PLC's corresponding A/B terminals, using a twisted-pair cable for best signal integrity over longer distances.
• What do the mA1 and mA2 terminals do?
  These are two independent 4-20mA current loop outputs, typically mapped to two of the measured parameters (such as pH on mA1 and EC on mA2), for direct analog integration with legacy PLC systems.
• Do I need a separate power supply for the pH and EC probes?
  No, both probes are powered directly through the transmitter's internal circuitry once the transmitter itself is connected to 12-24V DC — no separate probe power is needed.
• Why is my PHEC 1.0 showing no reading on the display?
  This is usually a power supply issue — confirm your DC supply is within the 12-24V range and that VCC/GND polarity is correct at the terminal block.
• Why are my pH readings drifting or inaccurate?
  This is typically caused by an uncalibrated probe or a dried-out reference junction  recalibrate using fresh pH buffer solutions (4.00, 6.86, 9.18) and ensure the electrode tip stays wet between uses.
• Why is my RS485 communication not working?
  Check that A and B wires aren't swapped, confirm your converter's baud rate matches the transmitter's default setting, and verify a common ground exists between devices.
• Why does my EC reading seem stuck at zero?
  This usually means the EC probe's 4-wire connector isn't fully seated, or the probe is not properly submerged in the solution being measured — verify both connection and immersion depth.