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HYDROS 21 Conductivity, Temperature, Depth Sensor CTD-10 Upgrade



  • Brand: METER
  • Model: HYDROS 21
  • Product description: The problem with most water depth, temperature, and electrical conductivity sensors (CTD sensors) is that their cost is prohibitively high. Plus they often require an extra barometric pressure sensor
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HYDROS 21 Conductivity, Temperature, Depth Sensor CTD-10 Upgrade Description:

User's Manual

No need for costly extra sensors

A compact 3.4 cm diameter water level sensor that fits into tight spaces, the HYDROS 21 CTD sensor 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 or any other logging system, 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.

Water level sensor with easy, research-grade data in real time

One of the qualities that makes the HYDROS 21 water level sensor 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.

Affordable, accurate, and reliable

While engineering the HYDROS 21 water level sensor, 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.

Best price-to-performance ratio on the market

Trying to measure water level, temperature, and EC typically requires an expensive CTD 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.


CTD sensor continuously monitors groundwater and surface water level changes

Vented sensor means no need for an additional sensor to measure and reference barometric pressure

Integrated electrical conductivity and temperature measurement

3.4 cm diameter sensor that fits into tight spaces

Low cost


Easy to use

HYDROS 21 Conductivity, Temperature, Depth Sensor CTD-10 Upgrade Specificationx:

Measurement Specifications Water Depth Range: 0 - 10,000 mm
Resolution: 1 mm
Accuracy: ±0.25% of full scale at 20 °C
NOTE: Depth measurement accuracy assumes no abrupt temperature variations.
Temperature Range: -40 to +60 °C
Resolution: 0.10 °C
Accuracy: ±1.00 °C
NOTE: The pressure transducer may be damaged or destroyed if frozen in ice. Remove the sensor if the water temperature could drop below 0°C (32 °F).
Bulk Electrical Conductivity (EC) Range: 0 – 120 dS/m
Resolution: 0.001 dS/m
Accuracy: ±0.01 dS/m or ±10%, whichever is greater
NOTE: The EC measurement is corrected to a standard temperature of 25°C.
Communication Specifications Output DDI serial or SDI-12 communications protocol
Data Logger Compatibility METER ZL6 data loggers and any data acquisition system capable of 4.0- to 15.0-VDC power and serial or SDI-12 communications
Physical Specifications Dimensions Diameter: 3.4 cm (1.3 in)
Length: 9.0 cm (3.5 in)
Operating Temperature Range Minimum: 0 °C
Maximum: 60 °C
NOTE: Sensors may be used at higher temperatures under certain conditions
Cable Length 10 m (standard)
20 m)
40 m (maximum cable length)
Cable Diameter 6.00 ±0.25 mm (0.240 ±0.010 in) with minimum jacket of 0.80 mm (0.031 in)
Connector Types Stereo plug connector or stripped and tinned wires
Stereo Plug Connector Diameter 3.5 mm
Conductor Gauge 20-AWG signal and power / 21-AWG ground wire
Electrical and Timing Characteristics Supply Voltage (Power to Ground) Minimum: 4.0
Typical: NA
Maximum: 15.0 V
Digital Input Voltage (Logic High) Minimum: 2.8 V
Typical: 3.6 V
Maximum: 5.0 V
Digital Input Voltage (Logic Low) Minimum: -0.3 V
Typical: 0.0 V
Maximum: 0.8 V
Digital Output Voltage (Logic Low) Minimum: NA
Typical: 3.6 V
Maximum: NA
Power Line Slew Rate Minimum: 1.0 V/ms
Typical: NA
Maximum: NA
Current Drain (During Measurement) Minimum: 2.5 mA
Typical: 3.5 mA
Maximum: 8.0 mA
Current Drain (While Asleep)) Minimum: NA
Typical: 0.35 mA
Maximum: NA
Power Up Time (DDI Serial) Minimum: 52 ms
Typical: NA
Maximum: 100 ms
Power Up Time (SDI-12) Minimum: NA
Typical: 700 ms
Maximum: 750 ms
Power Up Time (SDI-12, DDI Serial Disabled) Minimum: NA
Typical: 175 ms
Maximum: 200 ms
Measurement Duration Minimum: NA
Typical: 450 ms
Maximum: 600 ms
Other Compliance Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)


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