Conductivity / Temperature / Depth Sensor


Why spend more for less?

The problem with most water depth, temperature, and electrical conductivity (EC) sensors is that their cost is prohibitively high. Not only that, but the measurement often requires you to purchase an extra sensor to make a barometric pressure reading to correct for atmospheric pressure. You need a low-cost instrument that’s equipped with every sensor necessary for things like tracking changes in solute movement, measuring groundwater recharge, and studying surface water hydrology. You need the HYDROS 21.

No need for costly extra sensors

A compact 3.4 cm diameter sensor that fits into tight spaces, the HYDROS 21 is a low-cost, durable, and easy-to-use tool for monitoring EC, temperature, and depth in both groundwater and surface water. More importantly, it’s an all-in-one instrument. When used with the ZL6 data logger, you won’t require an additional sensor for measuring—and referencing—barometric pressure. With a range of 0 to 120 dS/m and a measuring depth of 10 m, the sensor makes accurate depth and EC measurements for a broad range of applications.

Easy, research-grade data in real time

One of the qualities that makes the HYDROS 21 so easy to use is its fast plug-and-play compatibility with the ZL6 data logger (also compatible with Campbell Scientific data loggers). Plus, with the ZL6, you can monitor and remotely access cloud data wirelessly from any internet-connected computer or device in near-real time.

Best price-to-performance ratio on the market

Trying to measure water level, temperature, and EC typically requires an expensive sensor with integrated telemetry. Unlike competitor sensors, all of the HYDROS 21’s data management happens in an external data logger, so the cost of each individual sensor is lower. Now, instead of having to rely on a single point measurement, you can take readings in several different locations without exceeding your budget.

Affordable, accurate, and reliable

While engineering the HYDROS 21, we wanted to design a water level sensor that was not only highly accurate but also provided a high degree of value. Because of its low-complexity, low-maintenance, and low-cost design, you can be assured you’re getting an instrument that will save you time, hassle, and money.

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  • Continuously monitor groundwater and surface water level changes
  • Integrated electrical conductivity and temperature measurement
  • 3.4 cm diameter sensor that fits into tight spaces
  • Low cost
  • Durable
  • Easy to use



Water depth: 0 to 1,000 cm
Electrical conductivity: 0 to 120 dS/m
Temperature: -11 to 49 °C, do not expose to freezing temperatures if sensor is in water


Water depth: 2 mm
Electrical conductivity: 0.001 dS/m
Temperature: 0.1 °C


Water depth: +/- 0.5% of full scale @ 20 °C

NOTE: Depth measurement accuracy assumes no abrupt temperature variations

Electrical conductivity: ±0.01 dS/m or ±10% (whichever is greater)

NOTE: The EC is corrected to a standard temperature @ 25 °C

Temperature: ±1 °C

Operation temperature

0 to 50 °C (Pressure transducer cannot be allowed to freeze while submersed)

Power requirements

3.6 - 15 VDC, 0.03 mA quiescent, 0.5 mA during 300 ms measurement


9 cm (l) x 3.4 cm (w)

Measurement time

300 ms (milliseconds)


Serial TTL, 3.6 Volts Levels or SDI-12

Connector types

3.5 mm (stereo) plug or stripped & tinned lead wires (3)

Cable length

10 m standard; custom lengths available upon request

Data logger compatibility (not exclusive)

METER ZL6,EM50/60 Series, ProCheck, Campbell Scientific

Software compatibility

ECH2O Utility (rev 1.64+), DataTrac3 (rev 3.4+)

California requires the following notice:

⚠️ WARNING: This product may contain chemicals including ethylene glycol, lead, nickel, styrene and cadmium, which are known to the State of California to cause cancer, birth defects or other reproductive harm. For more information, go to www.P65Warnings.ca.gov



Have a question or problem? Our support team can help.

We manufacture, test, calibrate, and repair every instrument in-house. Our scientists and technicians use the instruments every day in our product testing lab. No matter what your question is, we have someone who can help you answer it.

Phone US: +1 509-332-5600
Phone Europe: +49 89 12 66 52 0


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