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HM Digital COM-300 Waterproof Pro Series pH/TDS/EC/Temp Water Quality Test Meter (GT28-COM-300-HM)

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Quick Overview
  • Genuine HM Digital COM-300 pH, EC, TDS & Temp Meter
  • Super Precise (98% Accuracy)
  • Pre-Calibrated & Reads Wide Sample Ranges
  • Upgraded Non-Linear Scales (pH, µS, mS, ppm, ppt)
  • Conversions at the Click of A Button
  • High Quality Rivals Expensive pH, TDS & EC Meters
  • Test salinity, drinking water quality, scientific testing, mixing nutrients/fertilizers, gardening, hydroponics, monitoring boilers, coolers, pools, spas, aquariums, wastewater, and more!
4 Interest Free Payments of $85.00

HM Digital COM-300 | Water Quality Test Meter | Measures Electrical pH, Conductivity (EC), Total Dissolved Solids (TDS), Salinity & Temperature (°C)

The HM Digital COM-300 is a sturdy, waterproof, professional-grade water testing meter that’s quick, reliable, easy to use, and simple to re-calibrate.

The COM-300 device comes pre-calibrated to give you accurate and reliable readings of pH, electrical conductivity (EC), total dissolved solids (TDS), and temperature (°C Degrees Celsius), and has limitless applications from drinking water quality or scientific testing, mixing nutrients/fertilizers for gardening and hydroponics through to monitoring boilers, coolers, pools, spas, aquariums, and even wastewater!

Capable of reading an incredibly wide range of sample data with over 98% accuracy on five upgraded non-linear scales (pH (acid/basic power of hydrogen), µS (micro-Siemens), mS (milli-Seimens), ppm (parts per million), ppt (parts per thousand)), the COM-300 meter also enables precise and quick conversions with the click of a button.

Designed in the US and manufactured with innovative Korean tech expertise, this solid bit of kit is built to last and rival more expensive TDS & EC meters, without the exorbitant price tag.

Features, Performance, Specs & Certifications

  • Incredibly Precise Measurements - 98% accuracy (within +/- 2% of the true parameter) and comes pre-calibrated based on a 1413µS solution.
  • pH (Power of Hydrogen Acid/Base) Range: 0-14 pH
  • Electrical Conductivity (EC) Range: 0–9990 µS (micro-Siemens) and 0 – 9.99 mS (milli-Seimens).
  • Total Dissolved Solids (TDS) Range:
    • 0–8560 parts per million (ppm) (on an 0.7 Scale (442 Scale*))
      • *Note: "442 Scale" refers to a formula of salt and deionized water, in a ratio of 40% sodium sulfate, 40% sodium bicarbonate, 20% sodium chloride. This formula was developed by the Myron L Company over 40 years ago and remains the world's most accepted salt standard to this day.
    • 0 – 5000 ppm (0.5 Scale (NaCl - Sodium Chloride)); 0-5.00 ppt (0.5 Scale (NaCl - Sodium Chloride)
  • Temperature Range: from 0-55°Celcius, also features Auto Temperature Compensation (ATC) with three (3) temp coefficients. 
  • Measurement Range Resolution:
    • From 0-99 the resolution of the measurement range increases/decreases in increments of 0.1 µS per ppm, and increments of 0.01mS per ppt;
    • From 100-999 the resolution of the measurement range increases/decreases in increments of 1 µS per ppm; and
    • From 1000-9990 the resolution of the measurement range increases/decreases in increments of 10 µS/ppm.
    • Temperature resolution increases/decreases in increments of 0.1°Celcius.
    • pH resolution increases/decreases in 0.1pH increments. 
  • Electrical Conductivity (EC) to Total Dissolved Solids (TDS) Conversion Factor: quick and easy non-linear conversions for KCl (potassium chloride), 442 Scale, or NaCl (Sodium Chloride) solutions.
  • Digital Calibration: easily calibrate to any point within the meter's specified range, with the push of a button (hold/mode). 
  • Large LCD Display: with dual test and temperature defaults for easy readings in all light settings.
  • Probe Sensor: made of platinum electrodes and a glass pH sensor with reference tube electrodes that are easy to detach and replace if required (Replacement Part No. SP-C3). 
  • IP-67 Waterproof Housing is submersible and buoyant so will float (and you don't have to worry about dropping it in the water).
  • Power: Auto-off function for up to 1000 hours of use. Takes 2 x Triple A (AAA) Batteries (included).
  • Bonus: lanyard to prevent accidental drops and cap to protect the probe when not in use. 
  • Weight & Dimensions: Light Pocket-Sized Device - 101.5g & 18.5 x 3.4 x 3.4 cm
  • 1 Year Warranty


Can I test for hardness with a TDS Meter?

Sort of, but not really. Hardness is a measure of the amount of dissolved calcium and magnesium within the water. A TDS meter will measure the total dissolved minerals, salts, or metals in the water - but it won't tell you what those dissolved particles are or whether they are actually a cause for concern. To assess your hardness, ask for a report from your local water board (if you draw from a municipal water supply). Otherwise, if you are on bore water, we recommend getting your water analyzed


How to recalibrate an EC & TDS Meter? Use an Electrical Conductivity (EC) and Total Dissolved Solids (TDS) Calibration Solution!

For optimal calibration results of your COM-300 EC & TDS Meter, we recommend periodically recalibrating your meter with HM Digital™ TDS Calibration Solution (342ppm NaCl).

The HM Digital TDS Calibration Solution contains:

  • 342 ppm of NaCl (Sodium Chloride) at 25 degrees celsius
  • 362 ppm at KCL (Potassium Chloride) at 25 degrees celsius
  • 478ppm as "442" at 25 degrees celsius
  • 700µS/cm at 25 degrees celsius

For best results using TDS Calibration Solution:

  • For an accurate result, we recommend that you decant the required amount into a sterile container for calibrating your meter.
  • Only use the required amount needed for calibrating.
  • Discard the used contaminated solution.
  • For optimal performance, re-calibrate your meters periodically, or if testing TDS or conductivity levels in wide or different ranges.
  • All Calibration fluids should be stored in a cool place, out of the heat of the sun.

How to recalibrate a pH Meter? Use a pH Calibration Solution!

For optimal calibration results of your COM-300 pH Meter, we recommend periodically recalibrating your meter with HM Digital™ pH 7.0 Buffer Calibration Solution.

For best results using the pH Calibration Solution:

  • PH-P7 is a quality pH 7.0 calibration buffer solution produced with high-quality salts and deionized water.
  • The solution is accurate +/- 0.02 @ 25 C and traceable to NIST standards.
  • Never touch the sensor with your fingers.
  • For additional instructions, consult the meter's user guide.
  • This product contains concentrated material(s) that may be harmful to human health. DO NOT DRINK.
More Information
Type Test Meters

Return Policy

Due to the nature of the products we sell, a strict return policy is in place. We work with food-grade certified materials that must be un-opened and un-used, so as to be able to be re-sold. This policy falls in line with the Australian Consumer Law, which is designed to protect BOTH BUYERS AND SELLERS. 

You may receive a refund or credit of equal amount, less the Restocking/Out-of-Pocket Shipping Expense Fee, if applicable, and any other deductions that are relevant. 

  • 30-Day Returns Policy: Returns will not be accepted without prior approval or after 30 days of the invoice date.

  • Wrongly Purchased Items/Changes of Mind Policy: Wrongly Purchased Items, or Change of Mind Purchases may be returned for a merchandise credit. This applies to, but is not limited to purchases of products that are:
    • The Wrong Size;
    • The Wrong System;
    • The Wrong Replacement Pack;
    • Due to a Change of Mind;
    • Due to Buyer Error, whereby the buyer has failed to conduct proper due diligence (including contacting FSA prior to purchase in order to clarify the relevant technical specifications, compatibility, requirements etc.) to ensure the product purchased from us is the correct product for their requirements.
  • Restocking/Out-of-Pocket Shipping Expense Fees Policy: All returns will incur a 17.5% restocking fee OR an out-of-pocket shipping expense fee, whichever is greater. 
    • This fee is in place to cover the administrative expense incurred in processing the return and/or the out-of-pocket expenses incurred by us in shipping the item to you. FSA may use its discretion to determine the restocking fee. Please note this policy falls in line with the ACL, and is designed to protect us as the seller from losses incurred due to buyer error. This means that you will NOT receive a full refund of the original purchase price - you will bear the cost of shipping the product back to us, and then you will receive a credit equal to the purchase price of the product LESS the Restocking/Out-of-Pocket Shipping Expense Fee. Please refer to our Shipping Policies (below) for further clarification.
    • Low-Value Returns: Please note that with low-value items, sometimes the cost of sending the item back to us may be more expensive to you, than simply keeping the item. For example, let's say you have ordered 3x meters of the wrong-sized tubing for your needs and paid $12.00. If, for example, it cost us $7.69 to send the item to you, and it would cost you $7.69 to send the item back to us, overall you would be $3.38 worse off (due to incurring $7.69 to send the item back to us, and having $7.69 taken out of the credit) than if you had kept the item and re-ordered the correct product for your needs. 

  • Shipping Policies: 
    • Free Shipping Offer: As part of our offer of Free shipping Australia-Wide, FSA reserves the right to select the most cost-effective courier to effect delivery of the product to you. We make no guarantee as to how long an item will take to arrive due to unforeseen circumstances outside of ours/the couriers' control, including but not limited to: Staff Shortages, Supply Chain Demand, Extreme Weather Events etc.
    • Express Shipping Policy: If you require an item on an urgent or Express basis, it is your (the buyer's) responsibility to contact us directly by telephone on [phone removed by eBay] prior to purchase, in order that we may quote you the options available for Express Delivery to your nominated address, and to organise additional payment for this Express Service. Express Shipping is not included in our offer of free shipping - this service will come at an additional cost payable by the buyer. 
    • Late Shipping Policy: Given that we offer the option for customers to organise Express Shipping with us prior to purchase, cancellations or refunds will NOT be issued on the basis of late or delayed shipping where the customer has opted for our Free Shipping offer. If the item (sent via Free Shipping), arrives late and the buyer wishes to return the item on this basis, the buyer will be liable for the cost of returning the product to us and a Restocking/Out-of-Pocket Shipping Expense Fee will be applicable to the return, as per the listed returns policy line items above. The customer will be issued a merchandise credit.
    • Our offer of Free Shipping does not apply to Returns: Whilst we offer Free Shipping, this does not mean that there is no cost to ship the product - obviously, a shipping expense is incurred, and as with all e-commerce operators that offer Free Shipping, the cost of shipping the product from our warehouse to your nominated shipping address is built into the price of the product. The offer of Free Shipping therefore only applies to the act of FSA supplying the product to you, and does not cover the cost of returning the product from the customer to FSA.
    • Returned to Sender Items: In the case of the buyer being unavailable to sign, refusing delivery, or the item being sent back to us for whatever reason, FSA may, at its discretion, pass the cost of the product being Returned to Sender (i.e. being returned back to us), back onto the buyer. Refer to Restocking/Out-of-Pocket Shipping Expense Fees (above).
    • Lost Parcels: If an item is deemed to be LOST IN TRANSIT by the courier, the customer is entitled to a replacement product or refund in line with the ACL. In the case of a replacement product, FSA reserves the right to send the replacement product in line with its Free Shipping offer. If you do require the replacement item urgently, please get in touch with our customer service team directly to organise Express Shipping. 

  • Product Damage & Product Faults: Any damage to products that are not reported to FSA within 48 business hours of receipted delivery is not covered under our transit warranty. Return shipping is to be paid by the buyer to the address provided by FSA. It is recommended that the customer applies a transit warranty to the return freight item/s, in case of damage.
    • Faults: Should the item appear faulty or doesn’t work as described, you must supply written/photographic/video evidence of the fault to us, so that we may assess whether the unit/item must be returned for testing (if requested). If testing is requested, return postage is to be paid by the buyer. 
      • If the unit/item is deemed to be faulty, compensation will be provided for the postage cost (proof of cost required). 
      • If the unit/item is deemed to be in working order and as described, the buyer will be responsible for the cost of return postage of the product from FSA's premises, back to the buyer. 
    • Minor Damage: Any damages (minor, that can be repaired) will incur a fee, that will be deducted from the total refund which will be equal to the cost of the replacement parts (List Price) and labour charges (if applicable) to repair the system(s). This will be separate from the Restocking/Out-of-Pocket Shipping Expense Fees.
    • Major Damage: Any damage considered to be major and not feasible for repair may be refused and the return request will be void. The customer will be responsible for the return freight or disposal of the damaged unit.

Returns are not accepted on special order items unless the manufacturer allows it. Applicable fees will apply.

If you have any questions about our return policy, please contact us before purchasing. This will also help to ensure you purchase the correct product that suits your requirements.