Ammonium & ISE Analyzers

With enhanced ion selective electrode



What It Does For You

The model FX-300-NH4 analyzer uses specially engineered ion selective electrode technology for real time trending to monitor or control Ammonium (NH4+) and other ions in water without the need for frequent grab sample analysis.

The low maintenance ion selective electrodes (ISE) electrodes have no refillable solutions and need only periodic cleaning.

One-point offset calibration with results from your portable grab sample or lab instrument is required and done without removing the sensor from service. 

Industrial Grade Sensor

Our heavy duty ion selective electrodes measure free ammonium (NH+4) in solutions from 5-60°C (140°F).

They're available in several mounting styles for heavy industrial processing or municipal drinking and wastewater treatment:

  • Sanitary or hot tap insertion
  • Fully submersible into a basin or tank
  • Inline twist lock mount
  • Front and rear mounting threads for inline immersion

pH Compensation

Optional pH compensation is available using our ammonia & chlorine gas resistant pH sensor in solutions over 7 pH with temperatures up to 105°C to calculate a total ammonia measurement: dissolved gaseous ammonia (NH3) and free ammonium (NH3 +NH+4 ).

Reagent Free Direct Readings

The combination electrode determines free ammonium ions directly using no reagents, no separate reference electrode and without the increased complexity of converting dissolved NH+4 to gaseous NH3 for measurement with a gas sensor.

Lower Cost Alternative

Sample conditioning analyzers are costly.

Our system has a lower acquisition cost and more importantly a lower cost of possession compared to other technologies.

With its reagent free operation and reduced maintenance and cleaning requirements, you get performance with a low cost of ownership.

Low Maintenance

The low maintenance electrodes have no refillable solutions and need only periodic cleaning and one-point offset calibration with your portable grab sample or lab instrument without removing the sensor from service. 


  • Drinking water monitoring down to 0.5ppm
  • Monitor and control free ammonium between grab sampling in chloramine production or boosting
  • Select wastewater treatment down to 1ppm depending on water chemistry
  • High temperature industrial processes   with special half cell construction for improved intrusion resistance.

Heavy Duty Sensor & Modular Analyzer

Rather than thin bodied lab grade sensors commonly offered,  we use only sensors designed to withstand the conditions found in wastewater treatment plants and industrial processes.

Various compounds available for the solid state reference system with double or triple junctions provide resistance to the compounds and temperatures that can kill standard sensors, allowing you to focus on your process and not your sensors.

The modular analyzer design gives you the flexibility to configure the FX-300 as a simple ammonium transmitter, a pH compensated total ammonia analyzer, or a multi-parameter analyzer for any combination of measurements such as ammonium, pH, conductivity, ORP in one enclosure.

Each separate measurement and function module includes a 3 digit LED display of ppm and temperature and scalable 0/4-20mA output. Optional RS-485 Modbus RTU output is available and comes standard with the pH compensation module.

Ion operating ranges are selectable between 0-10, 0-100 and 0-999ppm.

A special high range "K-PPM" option allows you to measure from 0-10,000 to 0-999,000ppm.

The system is very easy to operate using three buttons on the face of each transmitter. The actual sensor millivolt (mV) output can be displayed by pressing the down button while in ppm mode.

More options include support for integral or external signal preamplifiers for long cable runs or noisy environments, alarm relays with basic control functions, temperature output and data logging.

Download FX-300-HH4  Brochure & Specs



Ion Compensation Can't Work

A unique membrane and solid state reference system in the electrode provides improved life and more selectivity over potassium, which interferes with the measurement.

The sensor can measure ammonium in the presence of 20 to 30 ppm potassium ions while maintaining linearity and stability under the most common conditions found in wastewater treatment.

Some systems include a second potassium ion sensor in an attempt to compensate for the interfering ion.

Ion compensation doesn't work reliably in continuous field applications given the variance of these factors:

Constant exposure to the interfering ion beyond a sensor's capability deteriorates the electrode, affecting the reading itself while gradually reducing its output.

Process streams can have varying sample background, analyte and interfering ion levels as well as temperature.

Uncertainties inherent to sensors as well as the calibration accuracy of the three sensors involved tend to compound any error instead of reducing it.

Continuously changing process inputs are too complex to be corrected with a formula, and extremely difficult to account for in a laboratory much less in an online application.



Total Ammonia

Dissolved ammonia gas converts into the ammonium ion form in a reaction dependent upon pH and temperature.

The sensor can only measure free ammonium ions (NH+4) . But given the pH and temperature relationship, the total ammonia (NH3 + NH+4) can be calculated using an ammonia gas resistant pH sensor and pH compensation module FX-300-TOT.

The system, shown above, displays free ammonium, pH and total ammonia.



Other Ions Measured

Ions measured in environmental monitoring and other applications include:

Solid state type sensors are available for:

  • Fluoride
  • Bromide
  • Chloride - low level measurements up to 350 ppm
  • Iodide
  • Silver
PVC membrane based sensors are available for:
  • Ammonium
  • Calcium
  • Chloride -  high level measurements
  • Lithium
  • Nitrate
  • Nitrite
  • Perchlorate
  • Sodium

Note that the ammonium, nitrate and nitrate sensors are not suitable to measure at the low levels required in aquaculture process control.


Contact us  for more info