The HM Digital PSC-154 is a panel-mount controller that continuously monitors Total Dissolved Solids (TDS) or Electrical Conductivity (EC) and acts on it. When the reading reaches the user-set point, the unit lights a warning, sounds an optional alarm and switches an isolated dry contact to start or stop a pump, solenoid valve or other device. A simultaneous 4–20 mA output lets a PLC, SCADA system or chart recorder log the same value — which is what separates the PSC-154 from the otherwise identical PSC-150.
Typical duties: commercial and industrial RO permeate quality, DI polishing loops, cooling-tower and boiler blowdown, hydroponics and aquaculture nutrient control, and general process-water monitoring. Supplied complete with sensor, 3 m shielded sensor cable, power cord, mounting brackets and U.S. plug adapter.
| SKU / Model | PSC-154 |
| Product Type | Panel-mount TDS / EC controller & monitor with 4–20 mA output |
| EC Range | 0–9999 µS (µS/cm) |
| TDS Range | 0–9999 ppm (mg/L) |
| Temperature Range | 1–80 °C (33–176 °F) |
| Resolution | 0–999: 0.1 µS/ppm · 1000–9999: 1 µS/ppm · 0.1 °C/°F |
| Accuracy | ±2% of reading · Thermometer ±0.5 °C |
| Temperature Compensation | Automatic (ATC), 1–80 °C |
| Calibration | Digital push-button, with manual trimmer-pot fine-tuning in high ranges |
| Set Point | Single point, set by on-screen UP/DOWN buttons to any value in range |
| Set-Point Relay | Single, isolated dry contact — 2 A, max 220 V, resistive load, 100,000 strokes |
| Relay Control | Opens or closes a circuit via dry contacts when the ppm/µS level reaches or exceeds the set point — drives a pump, solenoid valve or other device |
| Relay Voltage | 5 V (the connected device requires its own power source) |
| Analog Output | 4–20 mA, max loop load 500 Ω (PSC-154 only) |
| Output Accuracy (mA) | ±1.5% |
| Alarm | Optional steady beep, user-selectable |
| Probe / Sensor | ½" NPTF bushing — replacement sensor model SP-1-PSC |
| Cable Length | 3 m (9.8 ft) shielded |
| Display | Bright tri-colour LED — simultaneous EC/TDS and temperature |
| Power Supply | 110 V / 220 V, ±10% Vac, 50/60 Hz |
| Enclosure | ABS, front and back |
| Operating Environment | 0–50 °C (32–122 °F); RH max 80% non-condensing |
| Panel Cut-Out | 67 × 67 mm (2-21/32" × 2-21/32") |
| Dimensions | 7.2 × 7.2 × 11.1 cm (2.8 × 2.8 × 4.4 in) |
| Weight | 241 g (8.5 oz) |
| Factory Calibration | 1413 µS NaCl solution (700 ppm) |
| Warranty | 1 Year Limited Warranty — controller and sensor |
Specifications transcribed from HM Digital’s User’s Guide Ver 2.2E (document 200828), the current revision supplied with the unit — linked below.
Connect terminal #6 (+) and #7 (−) to the PLC. The loop is externally powered — the receiving instrument supplies the drive current. Maximum loop load 500 Ω.
(µS × 0.0016) + 4 = output mA
(output mA − 4) × 625 = µS
| Measurement (µS) | Output (mA) | Measurement (µS) | Output (mA) |
|---|
| 0 | 4.000 | 500 | 4.800 |
| 10 | 4.016 | 1000 | 5.600 |
| 20 | 4.032 | 2000 | 7.200 |
| 30 | 4.048 | 3000 | 8.800 |
| 40 | 4.064 | 4000 | 10.400 |
| 50 | 4.080 | 5000 | 12.000 |
| 60 | 4.096 | 6000 | 13.600 |
| 70 | 4.112 | 7000 | 15.200 |
| 80 | 4.128 | 8000 | 16.800 |
| 90 | 4.144 | 9000 | 18.400 |
| 100 | 4.160 | 10000 | 20.000 |
| 1 / 2 / 3 / 4 | Sensor — blue / red / white / black |
| 6 (+) / 7 (−) | 4–20 mA output to PLC |
| 8 / 9 | AC 110–220 V power in (either wire to either contact) |
| 10 / 11 | Alarm buzzer — disconnect the blue wire to silence |
| 12 / 13 | Relay, normally closed |
| 13 / 14 | Relay, normally open |
📄 PSC-154 Data Sheet (PDF)📖 User’s Guide Ver 2.2E (PDF)The data sheet carries the full specification block, the panel cut-out template and the contact/wiring diagram. The User’s Guide adds installation, calibration, set-point programming and troubleshooting, and covers both the PSC-150 and the PSC-154. Both documents are published by HM Digital, Inc.
1 Year Limited Warranty (controller and sensor), HM Digital, Inc.
