Residual Chlorine Analyzer
Streaming Current Charge Detector

Chemtrac, Inc./ Products/ Streaming Current/ Streaming Current Charge Analyzer


Streaming Current Charge Analyzer

HydroACT with DURATRAC 4

The HydroACT Analyzer with DuraTrac 4 Streaming Current Sensor is Chemtrac’s most reliable and accurate Streaming Current Monitor, providing unique and versatile capabilities for optimizing coagulant or polymer dosing. With improved Streaming Current measurement capability, expansive I/O, state of the art chemical feed logic, and the ability to monitor additional parameters key to coagulation (e.g. pH, UV254, NTU), this revolutionary product offers a
dependable, comprehensive, and scalable approach for tackling virtually any water treatment scenario.

The HydroACT Analyzer with DuraTrac 4 Streaming Current Sensor is Chemtrac’s most reliable and accurate Streaming Current Monitor, providing unique and versatile capabilities for optimizing coagulant or polymer dosing. With improved Streaming Current measurement capability, expansive I/O, state of the art chemical feed logic, and the ability to monitor additional parameters key to coagulation (e.g. pH, UV254, NTU), this revolutionary product offers a dependable, comprehensive, and scalable approach for tackling virtually any water treatment scenario. A well designed interface gives the user easy access to frequently used features like zero offset. Intelligent diagnostics, service reminders, advanced alarm features, and optional email/text alerts all work together to notify the user when service is required or when process conditions having changed sufficiently to warrant attention.

Standard Features
  • Includes analyzer, DuraTrac 4 sensor, 1 analog output, and 25 feet of interconnect cable
  • 0.2 to 10 gpm sample flow capability
  • Quick-replacement, user serviceable parts
  • Easy push button zero offset
  • Advanced signal health diagnostics

Optional Features
  • Expandable sensor inputs and I/O
  • Up to 1000 feet of interconnect cable
  • Chemical feed control outputs
  • Data logging with MicroSD download
  • Modbus or PROFIBUS communications
  • Color display
  • Remote (internet) access

  • Capability of incorporating multiple measurements that are key to coagulation, such as pH, TSS/NTU, and UV254 organics
  • Multiple chemical feed control options with overfeed protection, start delay, setpoint ramping, and other advanced features
  • State of the art features like signal health diagnostics and pH compensation provides improved

The HydroACT Streaming Current Analyzer standard configuration includes version HA2 analyzer, 1 DuraTrac 4 sensor, 1 analog output, and 25 feet of interconnect cable. Optional features include relays, digital inputs, digital communications, expanded number of sensor inputs and analog outputs, color display, and data download capability. Maximum I/O capabilities and certain features are specific to the different versions of HydroACT as detailed below.

HydroACT Features HA2 HA4 HA8
Sensor limit* 2 4 8
Analog output limit* 2 4 8
Relay limit* 4 8 16
Digital Input limit* 4 8 16
On/Off threshold control optional optional optional
Advanced control (e.g. PID) optional optional optional
Color display  
Data logging and download  
Remote (Internet) access    optional optional
PROFIBUS, Modbus   optional optional

*Optional configuration limits. See above description for standard configuration of analyzer version & I/O setup. Optional configurations must be specified.


Sensor Options

Free Cl, Total Cl, Cl Dioxide, Chlorite,
Ozone, ORP, pH with Temperature, DO,
Conductivity, SCM, UV254 Organics,
TSS/NTU, Particle Counter

Available Output Types

Universal (0-20mA, 4-20mA, 0-10 VDC)

Relays (optional)

SPST electromechanical relays rated for
380 VAC, 6A max.
Alarms & Thresholds: user-configurable alarms and 2 userconfigurable
thresholds (for control)
Chemical Feed Control (optional) HA4 & HA8 only – PID, Feed Forward, Flow
Proportional, Timer – multiple loops
Communication (optional) Modbus ASCII/RTU (RS485), Modbus TCP
(Ethernet), Profibus DP
Data Logging (optional) Customizable data logs. 1 million records
can be logged internally, and downloaded
to MicroSD card.
Enclosure ABS flame retardant, IP65, Nema 4X
Display 4.3”, 480×272, 24 bit, grayscale
Optional: color (HA4 & HA8 only)
Dimensions HA2 & HA4 – 9.0” W x 12.2” H x 4” D
(230 mm W x 309 mm H x 1035 mm D)
HA8 – 18.0” W x 12.2” H x 4” D
(460 mm W 309 mm H x 1035 mm D)
Weight HA2 & HA4 – 4.5 lbs (2 kg)
HA8 – 9 lbs (4 kg)
Warranty 12 months from date of purchase


DuraTrac 4 Streaming Current Sensor


-1000 to +1000

Signal Gain User adjustable, 1 to 600x
Zero Offset User adjustable
Sample Flow Rate 1 to 40 Liters per minute
Gain & Zero Offset User adjustable, Manual or Automatic
Repeatability (Cond. Range)* Better than 2% from (10 to 250 uS)
Better than 3% from (250 to 500 uS)
Better than 5% from (500 to 1,000 uS)
Max Pressure 20 psi (recommend atmospheric drain)
 Probe Type  Quick-replacement cartridge with replaceable sleeve
 Sample Connections  1” FNPT
 Materials Contacting Sample  Delrin, viton, stainless steel
 Wiring Connections  1 ea. shielded, 4 conductor, 22 AWG
 Self Diagnostics  Motor – RPM, Signal Health
 Power Requirements  110 VAC, 1 A, 60 Hz
220 VAC, 1 A, 50 Hz (optional)
 Enclosure  NEMA 4X, fiberglass reinforced
 Operating Temperature  34° – 120° F (1° – 49° C)
 Dimensions  11.2” W x 9.2” H x 6.3” D
(285 mm W x 234 mm H x 161 mm D)
 Weight  10 lbs (4.5 kg)

*Repeatability/Accuracy specifications for most other SCM’s are only valid when conductivity is very stable. These instruments do not perform to their specification when conductivity changes by as little as 10%.

DuraTrac 3 & DuraTrac 4 / Operation Manuals Version Languages Size Date
HydroACT 4 DuraTrac 3 User Manual

HydroACT 4 DuraTrac 3 User Manual

3.4 MiB 11/15/2017
HydroACT 4 DuraTrac 4 User Manual

HydroACT 4 DuraTrac 4 User Manual

3.5 MiB 11/15/2017
Streaming Current User Guides Version Languages Size Date
Quick Start Guide HydroACT With DuraTrac 4

Quick Start Guide HydroACT With DuraTrac 4

1.0 MiB 11/11/2016
Streaming Current Charge Analyzer / Datasheets Version Languages Size Date
HydroACT & DT3 - Data Sheet

HydroACT & DT3 – Data Sheet

397.1 KiB 01/26/2018
HydroACT & DT4 - Data Sheet

HydroACT & DT4 – Data Sheet

867.6 KiB 09/13/2016
DuraTrac 3 & DuraTrac 4 / Other Documents Version Languages Size Date
DuraTrac 3 Operation Manual (Older Model)

DuraTrac 3 Operation Manual (Older Model)

1.8 MiB 02/11/2014
DuraTrac 4 Operation Manual (Older Model)

DuraTrac 4 Operation Manual (Older Model)

1.7 MiB 09/05/2014
Streaming Current Monitors (SCM) are used to detect the net charge of soluble (e.g. organics) and insoluble (e.g. colloidal particulate) species in water. This is an extremely useful measurement because the net charge of colloidal and soluble contaminants in water will determine whether those contaminants are stabilized in suspension, or destabilized enough with the use of cationic coagulants to allow for more efficient removal via settling or filtration. A Streaming Current Monitor will respond to changes in the feed water turbidity as well as organics. Natural organic matter (NOM) will generally produce a significant response on a Streaming Current Monitor due to its high anionic charge. The ability to measure charge responses associated with both organic and particulate contaminants is what allows Streaming Current Monitors to reliably optimize coagulant dosage.
Streaming current is a very small electric current which is developed when water containing electrolytes is rapidly passed across a surface, such as what occurs when water is forced through a thin capillary. An identifying feature of a Streaming Current or Streaming Potential measurement device, like those used in water treatment, is a reciprocating piston that travels inside of a probe. The probe itself is composed of a dead end bore with electrodes positioned at either end. The vertical up and down movement of the piston causes water to be pulled into and then discharged from the probe’s bore. The clearance between the piston and probe walls is usually very small (e.g. 0.010 in) and this serves to create the “shearing zone” that gives rise to the streaming current signal.

This Streaming Current arises due to these high shear forces acting upon a surface’s electrical double layer (EDL), which can be thought of as an atmosphere of charged atoms (ions) that appear on a wetted surface, such as the surface of a colloid, or in a larger context the surface of Streaming Current Detector’s piston. This atmosphere of charge is composed of a stern and diffuse layer (hence the term “double layer”) of positively and negatively charged ions. The shearing action of the water causes the separation of ions from the diffuse layer which in turn produces the “streaming current”. This signal is then amplified and processed by the SCM’s electronics where it is then displayed as the streaming current reading.

Zeta Potential (ZP) is the electrokinetic potential that exists at a colloids surface and is expressed in mV’s. Measurements of Streaming Current are not a direct measurement of Zeta Potential, although it is fair to say they are closely related for reasons described in the previous FAQ “How is the Streaming Current signal produced”. While it is useful to think of Streaming Current as a pseudo Zeta Potential measurement, it should always be made clear that any correlation between the two is not constant and trying to keep an online Streaming Current Meter reading calibrated to a laboratory determination of Zeta Potential is a very tedious task for most water plants and therefore rarely done.

It is more commonly accepted the relative measurement of electrokinetic potential provided by Streaming Current Meters is very useful as a process monitoring and control tool without needing to calibrate it to a ZP value, as long as the user makes occasional determinations of an optimum Streaming Current setpoint reading using jar testing or other methods (see FAQ “How do I determine my Streaming Current setpoint?).

Instruments used to measure Streaming Current go by many various names depending on manufacturer: streaming current monitor, streaming current analyzer, streaming current detector, streaming current meter, streaming potential analyzer, streaming potential detector, particle charge detector, particle charge analyzer, etc..

Some of these instruments will measure the electrical voltage potential (properly referred to as streaming potential) that results from the streaming current affect, while others measure the actual current itself. An instrument that is called Streaming Current might actually be technically measuring Streaming Potential.

It is an interesting fact that you will not see much agreement between manufacturers in how the Streaming Current reading is displayed. Some show the reading as -10.00 to +10.00, while another goes from -100.0 to +100.0, and while another still goes from -1000 to +1000. Part of the reason for this is because Streaming Current has long been accepted as a relative and unit-less number. So, decimal point or no decimal point is just personal taste of that manufacturer and not any kind of indication of measurement accuracy or sensitivity.

Chemtrac has adopted a range of -1000 to +1000 and uses the term “Streaming Current Value” (SCV) and sometimes “Streaming Current Unit” (SCU) for the units of measurement.

Online Streaming Current Meters (SCM) are used in various industries and applications. A very common use of Streaming Current Meters is for optimizing coagulant dosage in water treatment. The SCM allows the user to more accurately control the addition rate of the coagulant to maintain a setpoint charge reading that correlates to optimum treatment results. Other common applications for Streaming Current Meters include polymer control for wastewater treatment and wet end charge monitoring in the pulp and paper industry.
For many water treatment applications, if installation is done correctly and as advised by the manufacturer, then the odds are that a Streaming Current Detector (SCD) will provide a useful benefit and in many cases can be used to automate coagulant dosing. However, not all applications are a good fit for this technology. Water chemistry and the exact type of coagulant being used play a huge role in determining whether a Streaming Current Detector is a good fit. In some cases, the chemistry and coagulant selection are not the problem. The problem is sometimes to do with process design. Mainly in how and where the coagulant is being injected and mixed, and where a sample can be taken. In many of these cases, injection points and samples points can be moved around to better accommodate an SCD.

So how do you know if a Streaming Current Detector is the right choice for your application? Before making any decisions, we highly recommends a consultation with one of our application experts. Chemtrac has over 25 years of experience helping thousands of water treatment plants determine whether a Streaming Current Detector is the right tool for them. If we can’t make a confident determination over the phone, we will ask for samples to be sent to our lab for testing and/or come onsite to perform an onsite evaluation.

To help us determine whether a Streaming Current Analyzer is right for your application, please gather the following information before contacting our application specialist:

1) Type of coagulant and/or polymer being used (e.g. alum, ferric, PACl, ACH), as well as a listing of all other additives fed upstream of where the SCM sample is to be located. Provide expected min, max, and average dosages of each chemical. If feeding PACl, please determine the products basicity. For any coagulant aids or flocculants, be sure to determine whether these are cationic or anionic.

2) The min, max, and average values for the following water chemistry variables: pH, alkalinity, temperature, and conductivity.

3) The min, max, and average for these raw water quality and process variables: NTU (or TSS), organics (TOC), process flow rate.

4) Exact location where coagulant is being injected relative to other additives and mixing devices. A simple hand drawn diagram is very helpful.

5) Location where the SCM sample point will be located, and how far downstream in seconds/minutes that is expected to be from coagulant injection point. This is very important to determine somewhat accurately!

6) Location where the sensor will be mounted relative to the sample point. Its best to not use long sample lines if they can be avoided.

7) For water treatment, provide a listing of the plants water source(s). It is very important to note if the plant will sometimes switch source waters.

8) For wastewater, list the type of industry (e.g. food, petrochemical, paper, etc). Wastewater will require many more questions to be answered during the phone consultation.

This is a very important question and something that is often not well understood. The Streaming Current Analyzer should be installed as close to coagulant injection as possible. When it comes to charge measurements, seconds matter! In some situations, the cationic charge that appears with the introduction of a coagulant is very short lived. In some cases, it is so short lived that it is impossible to measure, and Streaming Current Analyzers can’t be used in those applications without chemistry modification or a change in coagulants.

Of course, there has to also be consideration given to mixing. If the mixing of the coagulant is poor, then the reading will be unstable if the SCM is mounted too closely to the injection point. In those cases, one should consider ways to improve mixing before deciding to move the sample point further downstream. This is because moving the sensor downstream often diminishes responsiveness. It can also leave the SCM setpoint more subject to variation and complicate PID control.

Ideally, the sensor will sample directly out of the rapid flash mix where the coagulant is added, or directly after a static mixer. Keeping the response time (or lag time) down to 30 seconds is ideal. But less than 1 minute is usually acceptable. How well a Streaming Current Aanlyzer will work with > 1 minute lag time longer is just going to depend greatly on water chemistry and type of coagulant being used. We advise contacting Chemtrac before making any decisions on where to install a sample point and permanently mount your sensor. This could save you thousands of dollars by not having to relocate the sample point later.

The first recommend step is to pour raw water that contains no coagulant through your sensor. If the sensor has already been running on treated water, it is advised to first clean your sensor as recommended in the manual beforehand. Its advised to slowly pour at least 2 to 4 liters of raw water through the sensor (smaller amounts can be used if the sensor was properly cleaned), and then adjust the gain for a reading of -150. Some customers may prefer a higher or lower value depending on how much response they see to their coagulant.

By adjusting the gain for a known reading on your raw water, you will know exactly what sort of reading to expect if you lose your coagulant feed. Also, you will have a clear idea of how much response you get to your treated water. For example, if raw water reads -150 and treated water reads -25, then you know that you are seeing around 125 unit response and an 85% reduction in your raw water charge reading. Anything better than a 50% reduction is good, and you want at least 100 units of difference between your raw water and treated water readings. If you results fall short of this, be sure to contact our application specialist to determine what next steps need to be taken.

When a new or recently cleaned Streaming Current Sensor is put into service, it can take anywhere from 5 minutes to 1 hour for the reading to stabilize. This stabilization time is often referred to as the “conditioning time”. This is because the probe and piston need time to fully condition their surfaces with the soluble and colloidal species in the water, and to reach an equilibrium with the sample. For various reasons, this can take longer in some cases, but usually requires less than 30 minutes.

Once a sensor has reached stabilization, the response to normal changes in water quality and coagulant dosing is much faster than the initial conditioning time and measured in seconds.

The cleaning frequency is going to be application dependent and determined by factors such as NTU, TOC, Iron/Manganese levels, and upstream additives (e.g. Potassium Permanganate can lead to sensor fouling). Many WTP’s can go weeks without needing to clean. In those situations, we recommend at least monthly cleanings. But in other cases, and especially in wastewater applications, more frequent cleanings will be required.

The best ways to determine when a cleaning is needed is to look for one of two things. The first is an unstable reading. A bouncy or erratic reading, where the reading changes rapidly from high to low in just a matters of seconds, is generally the result of a fouled probe or a probe with a loose fitting in the bottom of the probe. The second thing to look for is an unresponsive reading. This is often made evident by a slow drift in the pump speed that is not occurring with changes in water quality or flow. The following FAQ “How do I know my SCM is working properly?” provides more information on how to check response. If the reading is seen to be erratic or non-responsive, then a cleaning is recommended. Eventually, the customer will develop enough experience with the Streaming Current Sensor to determine a sensible routine cleaning frequency.

It is generally recommended to make a solution of Comet or Ajex, using 1 tablespoon per half liter of water. For tougher stains, especially arriving from iron/manganese, it is recommended to use a product like CLR or Hach Rover. It is not recommended to soak the probe and piston in cleaning solutions for more than a few seconds or minutes. And never use an acid to clean the probe.
To determine the ideal Streaming Current setpoint one first needs to determine the optimum dosage of coagulant. Jar testing is certainly a common method for determining the optimum dosage of a coagulant. We also highly recommend the use of Laboratory Charge Analyzer, like our model CCA3100, for quickly determining the optimum dosage of coagulant. Once the optimum dosage is determined, set the coagulant feed pumps to deliver that dosage

Wait for a few minutes after setting the optimum dosage for the Streaming Current value to stabilize. Once stable, the reading seen on the display can be used as the setpoint value by which to base future dosage adjustments. This reading can also be zero’d as discussed in the a following FAQ “What is the Zero Offset feature used for?”.

A common observation with streaming current controllers is that the setpoint does require adjustment from time to time. The changes to setpoint might be needed for various reasons, but the most common reasons have to do with changes in water chemistry (namely pH, alkalinity, and temperature). pH plays a very important role, especially when it comes to inorganic coagulants like alum. Other possible factors include adjustments to upstream additives, seasonal water temperature changes, large conductivity swings, and changes in water sources can all result in needing to re-optimize the setpoint.

Unfortunately, there are too many variables needed to make an accurate prediction of how often your setpoint will need to be changed. But generally speaking, a process that maintains stable pH (as measured at the SCM sample point) will fare better and require less frequent setpoint adjustments. Once again, we invite you to talk to our knowledgeable staff as we can provide a much clearer assessment once we have an opportunity to talk to you about your unique application details.

A useful feature of most Streaming Current Monitors is the ability to Zero the reading. This allows the user to make their ideal setpoint charge value equal to zero (0), which makes dosage adjustments easier to interpret. For example, if the ideal setpoint before applying the zero offset was -50, it might be difficult for an operator to interpret which way to adjust dosage if the reading went to -45. But if that reading of -50 was “zero’d”, then the offset reading would have gone from 0 to +5 when the true value went from -50 to -45. Seeing the positive number on the offset value gives a clearer indication that coagulant dose needs to be reduced (since the coagulant is known to drive the charge positive). Likewise, if the reading went from 0 to -5, it would be clearer from seeing the negative number that coagulant dosage needs to be increased.
Streaming current is more than a measurement of charge associated with suspended particulate. In fact, for many waters the streaming current reading is significantly more impacted by natural organic matter (NOM) than it is turbidity. This is because NOM carries a very high anionic charge in comparison to most particulate matter. So, even a small increase in total organic carbon (TOC) levels can cause the streaming current reading to move significantly in the negative direction. The ability to detect charge of both soluble and insoluble species is why streaming current meters are so useful in water treatment.
Streaming current detectors have even been shown to detect the presence of various chemicals that were accidentally introduced into a WTP’s source water. If your streaming current reading is going negative and turbidity is holding stable, it is advised to look at other measurements of water quality such as TOC, UV, BOD, and COD to determine if anything else is changing.
The simplest and easiest way to check to make sure your SCM is working is to simply make a 10 to at most 20% decrease in dosage for 5 minutes and note the response you see on your Streaming Current Monitor. That is an online verification test using your raw water and your coagulant, which is much more meaningful than most “verification” kits that will be discussed in the following FAQ “Do you have a calibration procedure for Streaming Current”.

For obvious reasons, some plants will not want to do the test described above. But the concerns of making a relatively small dosage adjustment of short duration should be weighed against the possible consequences of not doing these online verification test on occasion. Many WTP’s have assumed their SCM’s were working fine and only find out differently after their settled water NTU and filter effluent NTU started to climb due to a loss of coagulant feed.

Chemtrac does offer “verification solutions” that will clearly demonstrate the proper response of your Streaming Current Sensor where it matters the most, which is around neutral. We also offer ways to “calibrate” your gain setting to produce more consistent responses.

Chemtrac’s unique ability to verify the instrument response around neutral is important to understand because there are other suppliers who claim to have a calibration solution, but it’s just a solution with a very high dosage of cationic polymer which drives their reading well beyond the point of charge saturation. Streaming Current Analyzers will only go so far negative or so far positive before the reading flat-lines and becomes unresponsive to additional amounts of positive or negative charge. If you add enough polymer to a sample of water, it will send the Streaming Current reading to this max value and give a repeatable result, but it has no bearing on whether the sensor is working properly around a neutral charge.

A good analogy to help one understand our competitors calibration procedure better would be pouring in a 1,000 NTU standard into a turbidimeter that is designed to go no higher than 100 NTU, and then claiming that calibrating the turbidimeter to read 100 NTU using that 1,000 NTU somehow ensures an accurate or repeatable response at a value below 1 NTU. So, don’t be fooled, and definitely don’t pay good money for any calibration/verification kit that isn’t capable of checking the instrument response near neutral.

  • Come See us at WEFTEC (Booths 1841 & 1844) Posted on: 10/02/2017

    Chemtrac is in Chicago this week exhibiting at WEFTEC along with a few sister companies: NEFCO, Mass Transfer Systems, LEEM Filtration, Mer-Made Filter, and Sanborn Technologies. We are all owned by our parent company, North American Filtration, and we are sharing one 20’ x 50’ booth.

  • Video Testimonial: Lab and Online Charge Analyzers for Challenging River Water Coagulant Dosing Posted on: 08/07/2017

    The water treatment plant in King, NC has a source water that is quite a challenge to treat. The Yadkin River can experience quick and substantial changes in turbidity (NTU) and organics (TOC). Subsequently the required chemical feed dosages can be significantly impacted in a short period of time. Looking for the appropriate technology to help optimize their coagulation, settling, and filtration process, allowing them to produce the best water for their customers, they turned to two products from Chemtrac: the Laboratory Charge Analyzer (LCA), and the online Streaming Current Charge Analyzer (HydroACT Analyzer, and the DuraTrac 4 Streaming Current Sensor).

  • Chemtrac to Exhibit at ACE17 in Philadelphia Posted on: 05/25/2017
    The HydroACT Analyzer with DuraTrac 4 Streaming Current Sensor is Chemtrac’s most reliable and accurate Streaming Current Monitor, providing unique and versatile capabilities for optimizing coagulant or polymer dosing.
  • Another Successful Showcase at ACE 2016 Posted on: 07/30/2016

    The Chemtrac team joined attendees at ACE 2016 in Chicago, IL to discuss the latest models of Streaming Current Monitors, Particle Counters, Chlorine Analyzers, and HydroACT multi-parameter analyzer.   The Laboratory Charge Analyzer, a bench-top streaming current unit, was the featured product.

    As mentioned previously, the LCA builds on the success and solid performance of its predecessor models (CCA3100, ECA2100 and ECAT2100), allowing for charge neutralization titrations to accurately determine target coagulant dosages for surface water treatment. Essentially, the LCA provides a way for conducting jar tests in less than five minutes, as opposed to the traditional methods that can take in excess of an hour to run.

  • Happy Birthday Chemtrac, Inc. — Thirty One-derful Years! Posted on: 05/05/2016

    We are happy to say that this month marks the 31st anniversary of Chemtrac, Inc. Founded in 1985 upon the release of a new Streaming Current Monitor, Chemtrac has come a long way and is now recognized as one of the world’s leading manufacturers of Streaming Current Monitors and Particle Counters, as well as the provider of the HydroACT series of multi-parameter analyzers.

More News on Streaming Current

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