HM Digital COM-100L Professional EC/TDS/Temp Meter – IP-67 Waterproof
The HM Digital COM-100L is a professional-grade handheld meter that simultaneously measures electrical conductivity (EC), total dissolved solids (TDS), and temperature — across four selectable measurement scales — in an IP-67 waterproof, submersible housing that floats. Factory calibrated to 1413 μS, with push-button digital calibration to any point within range, automatic temperature compensation (ATC) using three selectable temperature coefficients, and a replaceable platinum electrode probe (SP-C1).
Designed for demanding professional applications: hydroponics, water purification, aquaculture, colloidal silver production, laboratory testing, pools and spas, boilers and cooling towers, wastewater regulation, and ecology testing.
Key Features
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Simultaneous EC, TDS & temperature measurement — all three parameters displayed at once on the backlit LCD; no mode-switching required
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Four measurement scales — μS, mS, ppm 0.5 (NaCl scale), and ppm 0.7 (442™ scale); select the scale that matches your application and calibration standard
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Automatic Temperature Compensation (ATC) — three selectable temperature coefficients correct EC/TDS readings for temperature variation, ensuring accurate measurements across changing ambient conditions
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IP-67 waterproof housing — fully submersible and floats; safe for field use, splash environments, and direct immersion in water samples
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Push-button digital calibration — calibrate to any point within the meter’s range without external tools; factory calibrated to 1413 μS
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Measurement Auto Hold — freezes the display when the reading stabilizes, allowing you to remove the probe from the sample before reading the value
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Data Hold function — manually freeze the display at any point for recording
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Replaceable sensor probe — model SP-C1 detachable platinum electrode probe; replace the probe without replacing the meter when electrodes wear
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Backlit large LCD display — easy to read in low-light field conditions
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Auto-off & low-battery indicator — conserves battery life; 2 x AAA batteries included
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±2% accuracy — professional-grade measurement accuracy across the full range
Four Measurement Scales Explained
The COM-100L’s four scales cover the full range of professional water quality measurement needs:
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μS (microsiemens) — direct EC measurement for low-conductivity water; standard for RO permeate, deionized water, and ultra-pure water applications
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mS (millisiemens) — direct EC measurement for higher-conductivity solutions; standard for nutrient solutions, process water, and wastewater
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ppm 0.5 (NaCl scale) — TDS calculated using the 0.5 conversion factor; standard for drinking water and water purification applications using NaCl calibration standards
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ppm 0.7 (442™ scale) — TDS calculated using the 0.7 conversion factor; standard for natural water, environmental testing, and applications using 442™ calibration standards (442™ is a registered trademark of Myron L Company)
Automatic Temperature Compensation (ATC)
Electrical conductivity is highly temperature-dependent — water conducts electricity better at higher temperatures, typically increasing EC by approximately 2% per °C. Without temperature compensation, EC and TDS readings taken at different temperatures are not directly comparable. The COM-100L’s ATC system applies one of three selectable temperature coefficients to correct readings to a standard reference temperature, ensuring accurate, comparable measurements regardless of sample temperature.
Ideal Applications
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Hydroponics & aquaponics — precise nutrient solution EC monitoring with ATC for consistent measurements across temperature-variable grow environments
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Water purification & RO systems — verify filter and membrane performance with TDS measurement across NaCl and 442™ scales
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Aquaculture — continuous water quality monitoring for fish and shellfish production
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Colloidal silver production — precise TDS/EC measurement for concentration control
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Pools & spas — water chemistry verification and treatment monitoring
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Boilers & cooling towers — process water TDS monitoring for scale prevention and treatment optimization
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Wastewater regulation — effluent conductivity measurement for compliance monitoring
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Laboratory & scientific testing — professional-grade accuracy with replaceable platinum electrodes and digital calibration
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Ecology & environmental testing — field-ready IP-67 waterproof housing for outdoor and aquatic sampling
Technical Specifications
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Model: COM-100L | Vendor: HM Digital
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EC range: 0–9,990 μS | 0–9.99 mS
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TDS range (0.7 scale): 0–8,560 ppm | 0–8.56 ppt
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TDS range (0.5 scale): 0–5,000 ppm | 0–5.00 ppt
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Temperature range: 0–55 °C | 32–130 °F
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Resolution: 0–99: 0.1 μS/ppm / 0.01 mS/ppt | 100–999: 1 μS/ppm | 1,000–9,990: 10 μS/ppm | Temp: 0.1 °C/°F
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Accuracy: ±2%
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ATC: Three selectable temperature coefficients
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EC to TDS conversion: Non-linear conversions for KCl, 442™, or NaCl — user-selectable
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Probe: Detachable platinum electrodes (replaceable; model SP-C1)
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Factory calibration: 1413 μS
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Waterproof rating: IP-67 (submersible; floats)
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Power: 2 × AAA batteries (included)
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Dimensions: 18.5 × 3.4 × 3.4 cm (7.3 × 1.3 × 1.3 in)
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Weight: 9.8 oz
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Origin: South Korea
Frequently Asked Questions
What does the HM Digital COM-100L measure?
The COM-100L simultaneously measures electrical conductivity (EC) in μS or mS, total dissolved solids (TDS) in ppm or ppt across two conversion scales (NaCl 0.5 and 442™ 0.7), and water temperature in °C or °F — all displayed at the same time on the backlit LCD.
What is the difference between the 0.5 (NaCl) and 0.7 (442™) TDS scales?
TDS is calculated from EC using a conversion factor. The 0.5 factor (NaCl scale) is standard for drinking water and water purification applications. The 0.7 factor (442™ scale) is standard for natural water, environmental testing, and applications using 442™ calibration standards. The COM-100L supports both, plus direct EC measurement in μS and mS, giving you four scales to match any application or calibration standard.
Is the COM-100L waterproof?
Yes. The COM-100L carries an IP-67 waterproof rating, meaning it is fully submersible and also floats — making it safe for field use, splash environments, and direct immersion in water samples without risk of damage.
What is Automatic Temperature Compensation (ATC) and why does it matter?
EC increases with temperature by approximately 2% per °C. Without ATC, readings taken at different temperatures are not directly comparable. The COM-100L’s ATC system corrects EC/TDS readings to a standard reference temperature using one of three selectable temperature coefficients, ensuring accurate, consistent measurements regardless of sample temperature.
Can I replace the probe on the COM-100L?
Yes. The COM-100L uses a detachable platinum electrode probe (model SP-C1) that can be replaced independently when the electrodes wear — extending the meter’s service life without replacing the entire instrument.
What is the COM-100L factory calibrated to?
The COM-100L is factory calibrated to 1413 μS. It also supports push-button digital calibration to any point within the meter’s range for field recalibration using your preferred calibration standard.
What applications is the COM-100L designed for?
The COM-100L is designed for professional applications including hydroponics, aquaponics, water purification, RO systems, aquaculture, colloidal silver production, pools and spas, boilers and cooling towers, wastewater regulation, laboratory testing, and ecology and environmental field testing.
What batteries does the COM-100L use?
Two AAA batteries, included in the box.
