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HYDROS 21
4. SERVICE
This section contains calibration and maintenance guidelines for the HYDROS 21.
Troubleshooting solutions and customer support contact information are also provided.
4.1 CALIBRATION
METER factory calibrates the water depth and EC sensors to values stored internally in
flash memory. The depth sensor is calibrated to known depths of water, and the EC sensor is
calibrated using potassium chloride (KCl) solutions of known concentrations.
relates EC at 25 °C for various concentrations of KCl, and these values can be used
to verify the HYDROS 21 EC sensor performance. The value outputs from the HYDROS 21 are
internally corrected to 25 °C.
Table 2 HYDROS 21 calibration values
Electrical Conductivity
(mS/cm)
Concentration of KCl in
Distilled Water
(g/kg)
100
0.0446
200
0.0930
500
0.2456
1,000
0.5120
2,000
1.0673
5,000
2.8186
10,000
5.8758
20,000
12.2490
4.2 CLEANING
Maintaining the HYDROS 21 is essential for consistent sensor performance. Inspect and
clean the HYDROS 21 frequently to prevent accumulation of microorganisms, plants,
sedimentation, or other debris.
4.2.1 PRESSURE TRANSDUCER
The HYDROS 21 ceramic piezoresistive sensor must be protected from sediment and debris.
If sediment or other debris build up on the pressure transducer, clean the membrane.
NOTE: Take care not to damage the pressure sensor.
Follow these steps to clean the HYDROS 21 pressure sensor:
1. Run water through the side slots of the sensor housing across the ceramic pressure
transducer to remove debris.
