• Amines in water – Water condensates
  • Salty water – Geothermal steams
  • Other water applications


  • In situ or extractive measurement
  • Low detection limit
  • Short response time
  • True T.D.S. measurement
  • Direct reading in mg/l or PPM/W
  • Long-life sensor
  • Interference-free
  • Low maintenance

The WATERSULF Series analyser is dedicated to the measurement of dissolved sulphides in water up to pH 8.5.

  • The concentration of Sulphides in water depends on the sample pH.
  • Between 0 and 6 the H2S is at the maximum concentration.
  • Between 6 and 8.5 the H2S concentration decreases.
  • Between 8.5 and 11 no H2S is present in the water.
  • Above 11 S־־ concentration increases.
  • Between 4 and 8.5 the HS־ increases.
  • Between 8.5 and 11.5 the HS־ is at the maximum concentration.
  • Above 11.5 the HS־ concentration decreases.
  • At neutral pH (7) only H2S and HS־ are present.
    The measurement principle is based on a variation of HENRY’s law :
    the weight of any gas dissolved in a definite volume of liquid is proportional to the partial pressure the gas exerts above the liquid at a constant temperature.
    The WATERSULF™ analyser incorporates :
  • an electrochemical sensor for sulphide (H2S)
  • a pH sensor (For calculation)
  • a temperature sensor (For calculation)
  • a pressure sensor (For alarm only)
    The sensors are connected to microprocessor electronics, which deliver a true concentration of T.D.S. calculated in relationship with the pH and temperature.

The H2S sensor is immersed in the water. The sensor is equipped with a propriety membrane. Due to the partial pressure effect, the membrane is only pervious to gases. No liquids, ions or solids can penetrate the sensing part.
The sensor contains a buffer solution with a redox catalyst and 3 electrodes. A defined polarization voltage is applied to the electrodes in order to give a well-defined concentration ratio of the oxidized/reduced redox catalyst. The H2S reacts, first chemically in presence of the redox catalyst to form a reaction product. Then, the electrochemical oxidation of the reaction product takes place at the measuring electrode.
Due to the polarization voltage effect, the system can adjust the concentration ratio. The resulting current is proportional to the dissolved molecular amount of H2S present in the sample.
The pH pressure and temperature sensors are also immersed in the water and deliver signals to the electronic module, which calculates the H2S + HS־. concentration on a real-time basis.

 1000 Panel Mounting, Safe area installation.
 3000 Ex-proof Probe, ATEX certified for hazardous area installation.
Electronic module 19” rack safe area installation.
 4000 Probe and electronic module, Ex-proof ATEX certified for hazardous area installation.
 5000 Portable battery-powered system, safe area installation.
MODBUS protocol
Calibration system
Remote control via Ethernet
Standing frame
Sampling system
For other options, consult factory

Measuring principleHenry’s Law. Detection of H2S / Sulphides using an electrochemical cell in relationship with pH and temperature.
Measuring ranges0.01-3 or 0.05-10 or 0.5-50 mg/l (to be stated). Other ranges, consult factory.
Range unitMg/l or PPM by weight (to be stated.)
Detection limit0.01 mg/l approx.
Response timeLess than 5s full scale (sample system excluded).
Resolution1μg/l (depending on the range.)
Linearity± 2% of the calibration full scale.
Reproducibility± 1% of the calibration full scale.
Accuracy± 2% of the instant value.
Cross sensitivityNone for the following components (% vol) :
– CO2 max 25.38 – H2 max 0.544 – CH4 max 5.78
– NH3 max 1000 PPM – CO max 92 PPM – CS2 max 5
– Organic solvents max 20 – Acetic acid max 1 mole/l – Salt – HCN
Yes for SO2 100 PPM equal 1 PPM H2S.
PH range0 – 8.5 (above on request)
Temperature0 – 30°C (above on request)
Pressure0 – 10 barg (above on request)
Area classificationGeneral-purpose for WATERSULF™ 1000 and 5000 Ex II 2G / Eexd II CT 6 ATEX certified.
For –20°C up to +40°C for WATERSULF™ 3000 and 4000.
Distance between probe and electronics1500m
RFI protectionI.E.C. 8013 Level 3
Sizes / WeightsDepending on the model. Refer to related schematics.
A – Detection probe module, equipped with 4 sensors   
1. – H2S / Sulphides 3. – Pressure 
PrincipleElectrochemical (Amperometric)PrinciplePiezoresistive
ResolutionLess than ± 0.1%Measuring range0 – 10 barg
Response timeLess than 1sBursting pressure15 barg
Accuracy± 2% of the instant valueResponse time150 ms
Temperature range0 – +30°CRepeatability± 0.1% of full scale
Bursting pressure10 barg max.Hysteresis± 0.1% of full scale
PH range0 – 8.5 (above on request)Accuracy± 0.1% on –5° up o +35°C
Shaft materialTitaniumTemperatureYes on given range
Sensitive tipGlassHousing materialStainless steel
PolarizationBuilt-in electronic boardSensor life24–36 months (depending on the application)
Sensor life9 – 12 months (depending on the application)  
2. – pH 4. – Temperature 
PrincipleSingle rod electrodePrinciple4 wire technique platinum resistor (Pt 100)
Measuring range0- 9 pHMeasuring range-2 up to +30°C
Accuracy0.05 pHResponse timeApprox. 1s
Response timeApprox. 1sRepeatability± 0.001°C
Bursting pressure15 barg.Accuracy± 0.01°C
Shaft materialTransparent plasticBursting pressure15 barg.
Thread materialStainless steel or titanium (on request)MaterialPlatinum, ceramic, titanium
Sensor life12–24 months (depending on the application)Sensor life24–36 months (depending on the application)
Probe power supply15VDC 35mA from the electronic module (galvanically isolated)
Probe electronicsOne PCB including :
DC-DC converter – RS 232 driver Micro controller – 4 channel 20 bit ADC
Temperature bridge – Pressure amplifier H2S amplifier – pH amplifier
One PCB for single-core transmission cable (FSK module)
Output signalRS 232 1200 Baud/s galvanically isolated
Probe diameter48 mm
Length440 mm
Connections2 ½” threads or flanges (to be stated) for general purpose in situ probe.
¼” NPT Female for ATEX version with Ex-proof box and sample chamber.
B – Electronic Module 
Power supply85 – 265 VAC 47 / 444 Hz 12VDC for Model WATERSULF™ 5000
DisplayLCD alphanumeric. H2S/ HS־ /, pH, T, P are displayed
Keyboard16 Keys, TOUCHSENSE™ type
Process alarm1 programmable with a built-in keyboard. Potential free relay contacts 3A 220V in N.O. or N.C. (to be stated). Relay coil normally de-energised or energised (to be stated).
Fail alarm1 potential-free relay contacts 3A 220V in N.O. or N.C. (to be stated). Relay coil normally energised (as Standard)
Analogue outputs4-20 mA self-powered, isolated, 600 ohms max. loop load (4 outputs available).
Digital outputRS 232 / 485.
Remote communicationETHERNET

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