HYDROS 21 Tech Specs
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Technical Specifications

Measurement Specifications
Water Depth
Range: 0.0000 – 10000.0000 mm
Resolution: 1.0000 mm
Accuracy: ±0.25% of full scale at 20 °C
NOTE: Depth measurement accuracy assumes no abrupt temperature variations.
Range: -40 to +60 °C
Resolution: 0 °C
Accuracy: ±1 °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: 1.0000 – 120.0000 dS/m 
Resolution: 0.0010 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
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
Length: 9.0000 cm (3.5 in)
Diameter: 3.4000 cm (1.3 in)
Operating Temperature Range
Minimum: 0 °C
Maximum: 60 °C
NOTE: Sensors may be used at higher temperatures under certain conditions; contact Customer Support for assistance.
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 0.031 in (0.80 mm)
Connector Types
Stereo plug connector or stripped and tinned wires
Stereo Plug Connector Diameter
3.5000 mm
Conductor Gauge
20-AWG signal and power / 21-AWG ground wire
Electrical and Timing Characteristics
Supply Voltage (power to ground)
Minimum: 4.0000 V
Typical: NA
Maximum: 15.0000 V
Digital Input Voltage (logic high)
Minimum: 2.8000 V
Typical: 3.6000 V
Maximum: 5.0000 V
Digital Input Voltage (logic low)
Minimum: -0.3000 V
Typical: 0.0000 V
Maximum: 0.8000 V
Digital Output Voltage (logic high)
Minimum: NA
Typical: 3.6000 V
Maximum: NA
Power Line Slew Rate
Minimum: 1.0000 V/ms
Typical: NA
Maximum: NA
Current Drain (during measurement)
Minimum: 2.5000 mA
Typical: 3.5000 mA
Maximum: 8.0000 mA
Current Drain (while asleep)
Minimum: NA
Typical: 0.3500 mA
Maximum: NA
Power Up Time (SDI-12)
Minimum: NA
Typical: 700 ms
Maximum: 750 ms
Power Up Time (DDI Serial)
Minimum: 52.0000 ms
Typical: NA
Maximum: 100 ms
Power Up Time (SDI-12, DDI Serial disabled)
Minimum: NA
Typical: 175 ms
Maximum: 200 ms
Measurement Duration
Minimum: 0.0000 ms
Typical: 450 ms
Maximum: 600.0000 ms
Manufactured under ISO 9001:2015
EM ISO/IEC 17050:2010 (CE Mark)