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DM3 Dual Inline EC/TDS Monitor

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Product Description

The DM3 is a commercial-grade EC/TDS monitor measuring at two independent probes.  The DM3 features a large backlit screen that displays readings from both probes simultaneously.  With its shielded cables and diagnostic messaging this robust device is ideal for Reverse Osmosis (RO) systems, or anywhere that two locations must be monitored.  


  • Highly efficient and accurate due to its advanced microprocessor technology.
  • Displays EC and TDS levels for two locations.
  • The unit backlight shuts off automatically after 3 minutes.
  • Factory Calibrated with a 342 ppm NaCl solution. The DM3 features digital calibration, and each probe can be calibrated independently.
  • Diagnostic error messaging.
  • Shielded sensor cables.
  • Comes equipped with quick connect fittings for the probes.
  • Installs quickly and easily.

Differences from the DM1:

  • Designed for commercial/industrial applications.
  • Stronger, water-resistant casing.
  • Digital calibration can be done individually on each probe/line.
  • Improved design, including an extra large, easy-to-read backlit LCD display.
  • Longer, waterproof, shielded cables.
  • Magnetic mounting bracket.


EC: 0 to 9999μS or 0 to 9.99mS
TDS: 0 to 5000ppm or 0 to 5ppt
Accuracy: ±2% of the reading
Conversion Factor: NaCl (avg. 0.5)
Cable Length: 46" (including sensor), shielded cables
Digital Calibration: Digitally factory calibrated to NaCl 342 ppm. Re-calibration can be done separately for each probe.
Power source: 2 x AA batteries (included)
Size: 4.6 x 2.8 x 0.7 inches
Weight: 8 ounces (with batteries)

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Product Reviews

  1. Amazing Quality to Value! 5 Star Review

    Posted by on 30th Jan 2024

    I purchased this for my aquariums RO/DI system. Out of the package the unit is well built. The wires are fully shielded/insulated unlike cheaper HM units and the backlit screen and user-selectable units are a very nice touch. It also comes with a magnetic mounting bracket with adhesive which made installation very simple (and future maintenance too!). To check it's accuracy I I compared it to a Myron L AR-1 Conductivity meter that has been calibrated by a third party. The Myron L AR-1 read my RO/DI water at 0.6 uS/cm. The DM3 read my water at 0.5-0.6 uS/cm. I was pleasantly surprised that the DM3 even got in the ballpark of the AR-1 since the AR-1 is over a $1000 conductivity meter. This is a slam dunk product that I think you'll be happy with. Buckeye Hydro was great too, I received the item 2 days after ordering it!

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