You will find answers to common questions relating to products, warranties, and returns below. If you are having issues operating a product, try visiting our troubleshooting page.



Contact the Sensorex Sales & Customer Service Team by phone +1.714.895.4344 and we’ll be happy to assist you.

Our tech support team is happy to answer any questions. Please visit and fill out the support form. A member of our technical support staff will be back in touch within one business day.

For other general questions about all Sensorex products, please contact customer service via our online form or call us directly at +1.714.895.4344


Yes. The output signal and impedance of all pH/ORP electrodes are compatible with virtually all meter and controllers. When ordering, please specify the type of connector, the temperature compensation (if using Automatic Temperature Compensation), and the installation configuration (if installing in a tank or pipe).

Check out this post for more information on selecting the right online pH/ORP sensor.

No. Due to the hazardous materials (mercury and mercurous compounds) used in Calomel electrodes, Sensorex has developed an alternative calomel free pH electrode using non-hazardous materials. Calomel electrodes were primarily used in applications involving proteins, sulfide, Mercaptan and silver ions. These materials react with the silver ions in the typical reference solution/gel and precipitate at the reference junction, plugging the junction, creating a reference junction potential, and/or contaminating the reference solution/gel. Sensorex offers a calomel free design or a conventional double junction design with no silver or chloride ions in contact with the sample. The classical problems (hysteresis, instability, and short life at elevated temperatures) characteristic of Calomel electrodes are eliminated with the Sensorex Calomel Free or Conventional Double Reference Junction design.

Yes. However, if your application involves proteins, a Sensorex double junction electrode is recommended. Proteins will react with the silver ions in the typical reference solution/gel and precipitate at the reference junction, plugging the junction, creating a reference junction potential, and/or contaminating the reference solution/gel. Sensorex offers a calomel free or a double junction design with no silver or chloride ions in contact with the sample. If your application involves low ionic (less than 100 microsiemens) samples, Sensorex also has a low ionic electrode which will provide greater stability and longer life in these applications. Contact the factory for these specific applications.

Each Sensorex pH electrode is supplied with a soaker bottle or storage cap containing soaker/storage solution. If you no longer have the solution, you can purchase it by pint bottles from Sensorex (part number S16). If soaker solution is not available, you can use the following in order of preference: 4 pH Buffer 7 pH Buffer Tap Water Note: Do not store any pH electrode in DI water. DI water is for rinsing, not storing.

Standard pH electrodes contain 3.5M KCl as a reference gel. Samples like DI water and other low ionic solution contain very small amounts of salt. These solutions try to leach ions from the reference gel to raise their conductivity levels. This results in very slow, sluggish, and unstable readings from a conventional pH electrode. Sensorex offers any model in double junction electrode in a special low ionic configuration which addresses these measurements difficulties. Contact Sensorex for more details.

All pH electrodes provide a high impedance millivolt signal. This signal is amplified by a pre-amp. The pre-amp is typically built into the instrument or controller, but can be a separate component or even built into the electrode. Normally, cable runs under 25 feet are not a problem for the millivolt pH signal. If you want to ensure a strong signal or need long cable runs, the Sensorex pHAMP-1 battery powered amplifier can ensure quality signal transmission. If you are using an S8000 platform solution, there is a simple EM800 add on module that can be used. Contact Sensorex for more details.

Using a flat measuring surface in agitated turbulent flow will minimize coating problems on the measuring surface of the electrode. The coating tends to move off the measuring surface since the entire surface is exposed to flowing sample. Normal spherical bulb measuring surface have a dead flow area which promotes coating buildup.

Sensorex and all manufacturers’ pH electrodes conform to the Nernst Equation for pH output as a function of temperature. At 25 degrees C, the pH output is 59.16 millivolts/pH unit. The electrode will give zero output at a pH of 7.0 at all temperatures.

pH glass impedance goes up as temperature goes down by a factor of 2.5 times for each 10 degrees C change in temperature. For example, if the glass impedance is 100 Megaohms at 25 degrees C, it will be 250 Meg ohms at 15 degrees C. Higher impedance slows down the electrode’s speed of response to changing pH levels. This is characteristic of all pH electrodes.

As a pH electrode ages, the impedance of the pH sensitive glass increases causing the output signal to become slow, sluggish, or drifting. Zero will shift beyond the adjustable range and span will shorten. In most typical applications, a pH electrode will function for 6 to 24 months. However, in fluoride applications or very caustic applications, the typical pH glass has a much shorter life. See our section on Fluoride Resistant electrodes for these applications.
All pH electrodes will have a small amount of offset as manufactured. The zero adjustment on your meter is designed to correct this offset. Consequently, you must calibrate the meter and electrode together, as a system. Sensorex supplies a pH Checker to calibrate or isolate a problem to your meter or electrode. But final calibration must be performed with the electrode connected to the meter. Sensorex also supplies buffers for performing pH and REDOX system calibrations.

The most common cause for this problem is an electrical ground loop in your system. To verify this problem, remove the electrode and calibrate it with a known buffer solution in a beaker. If the electrode measures within specification (stable and adjustable zero) when calibrated, place a copper wire in the beaker and the other end in your system. If the reading become unstable or shifts, a ground loop is your problem. The source of the ground loop could be any motor, pump, conductivity probe, or other electrically powered device in the media with the pH electrode. Do not attach the conductivity probe or any other electrically powered device to the same ground on your meter or controller as the pH electrode. You can also try placing a large (12-14 AWG) copper conductor into the media and the other end to the meter/controller ground terminal to draw the ground loop away from the pH electrode.

There are three possibilities to explain these observations:

  • the electrode sensing surfaces may be coated
  • the electrode may be reaching its useful life (typically 6 to 24 months)
  • a low ionic (conductivity below 100 microsiemens) media is being measured.

Call Sensorex to obtain a quote for our special low ionic pH electrodes for these applications.

A 2% – 5% hydrochloric acid (HCl) solution will dissolve most coatings. It is best to use a cleaning chemical that will dissolve the coating on the pH glass but not harm the materials of construction of the pH electrode. Refer to the specific product data sheet for materials of construction.

If your application includes proteins, heavy metals (Ni, Cd, Cu, Cr, Ag), sulfides, cyanides or iodides, or any other material which will react with silver or chloride ions, a Double Junction electrode will provide added protection and last longer.


Yes. The output signal of all ORP electrodes are compatible with virtually all meters and controllers. When ordering, please specify the type of connector, the length of cable, and the installation configuration (if installing in a tank, pipe tee, or insertion). You can read ORP output with most DVM’s (digital volt meter).

ORP is expressed in millivolts (mV). A range of -1000 mV to 1000mV is common with most ORP instruments.

ORP measures the total activity of a solution in mV or the total of reducing and oxidizing activities in a given solution. Practically speaking, ORP is useful for monitoring and controlling chemical addition of oxidizing or reducing agents. Oxidizing agents include chlorine, bromine, and ozone. Reducing agents include cyanide and sodium bisulfite and metabisulfite.

An ORP electrode employs a nobel metal such as platinum to sense electron transfer in oxidizing and reducing reactions. ORP senses the total electron transfer, or more simply if a chemical mix has more oxidizers than reducers in it. Nobel metals such as platinum, silver, or gold are used because they can sense the electron transfer but are not consumed in the reactions.

Some common applications for measuring ORP include:


  • Control of chlorine addition in swimming pools
  • Fruit and Poultry washing (disinfection)
  • Cyanide destruction in plating
  • Hexavalent chromium reduction
  • Mining application,
  • Control/monitoring of ozone addition in swimming pools and aquariums or purification of water prior to bottling or use in sterile solutions.
  • Bromine addition for disinfection of pools and spas is also common.

ORP does not have to be “calibrated” but it can be tested if desired or required. Standard ORP Test Solutions with stable mV outputs are required. Two types of solutions are available. One type requires you to mix pH buffers 4 and 7 with quinhydrone. These offer two different stable values, but the shelf life is only several hours and they cannot be stored. Sensorex part number B125 is a complete kit with everything that you need to complete two-point testing.

Sensorex also offers premixed solutions: B225 has a stable output of 230 mV while B425 has a stable output of 450 mV. Shelf life of these solutions is guaranteed for 12 months. 


We offer installation kits to support the following installation types:

  • Open channel / submersion
  • Closed vessel / in-pipe
  • Bypass / sampling

Maintenance intervals can very significantly depending on application and the environment in which the instrument is installed. We suggest comparing the output of the online unit to a grab sample measured by another UVT meter to confirm calibration accuracy 1-3 times per week. A visual inspection of the unit is recommended monthly.

We recommend calibrating the unit with DI water once per week for most accurate results.

The battery for the UVT-LED-H will last for approximately 350 measurements.

The two-year limited warranty covers any defects in materials and workmanship. The warranty does not cover damage caused by misuse, use outside specifications, or accidents. For more details, review our Warranty Policy.


Yes, but very infrequently if you use Sensorex DO6400 or DO7400 series. DO6400 and 7400 series can provide more than nine months of trouble-free service. DO Maintenance kits are available with all parts and solutions required for maintenance.

Yes. It is important that the membrane used on the sensor be clean and clear of any biological or other materials. Simply wiping with as soft cloth can do the job. For heavy fouling applications such as open pond aquaculture or waste treatment, we recommend using an automated cleaning device.

Sulfides will cause a precipitation reaction at the cathode. However, sulfides are rarely encountered in most applications.

Sensorex offers both PTFE and HDPE membranes. Although HDPE membranes provide faster response and higher output, the PTFE membrane provides more mechanical strength and still has a fairly quick response time (95% in two minutes or less). We recommend the PTFE membrane for our submersible DO sensors, especially in aquaculture applications.


Conductivity is used to measure the amount of dissolved solids in a solution or the concentration of acid or base..

This can be a somewhat complex answer. A conductivity sensor has a known AC voltage passed from a “sending” side, through the solution being measured, and out to the “receiving” side. The current in the circuit is measured. Using Ohm’s Law, V = IR, R, the “Resistance” across the water is calculated. Conductivity is 1/R.

Depending on the range, conductivity is expressed in µS (microSiemens) or mS (milliSiemens). When very low conductivity is measured, (if <0.1µS) it is often expressed as resistivity (Megaohms) rather than conductivity. In the past, conductivity was expressed as in micromhos or millimhos. The mhos units are now expressed in Siemens or fractions of Siemens.

Conductivity is greatly affected by temperature. An error of 2 – 5% per degree Centigrade is common and depends on the range of conductivity being measured. Generally, 2% error is most common for above 500uS. Lower conductivity especially values expressed as resistivity (ultra-pure water = 18.2 Megaohms = 0.055 uS) have up to 5% error. Your conductivity instrument will make these corrections automatically if a temperature sensor is used.

Use mild cleaning agents such as detergents or 5% HCl (removes scaling deposits). Always soak electrodes in chemicals and do not use toothbrush or wire brushes to clean since these will effect electrode performance.


Yes. Amperometric Sanitizer sensors require a controlled flow rate between 0.2-0.6gpm. Sensorex advises that the sensor is installed in flow cell FC72 and used with FM001 flow meter or a product similar to it.

The frequency for changing the membrane cap can vary significantly based on the application for use. The cap should be replaced when damaged or when readings are erratic or elevated in comparison to a DPD test.

The electrolyte should be drained and refilled approximately every 60 days.

Yes, this is very important. A sensor that is new, has had maintenance, or has been out of flow should be equilibrated in flow for 12 hours before use.

The amperometric sensors generate 4-20mA output and are factory scaled to specific range of 0-2ppm, 0-5ppm, or 0-10ppm.

Yes, the amperometric sensors require 12-24V DC with minimum of 250 mA. Maximum load is 1 Watt.

Free Chlorine is affected by pH and must be within 5.5-8.0 range. CLO2 and total chlorine are not affected by pH. All sensors are affected by temperature. The sensors should not be used in water containing surfactants, organic chlorine, or stabilizers such as cyanuric acid, ozone, or bromine.

Amperometric sensors are calibrated to a DPD test on a grab sample. The sensor’s 4-20mA output is adjusted to a value equal to the ppm reading of the DPD test.

We recommend that the sensor is stored at 5°C – 50°C ONLY and maximum humidity of 90% (non-condensing). Based on the amount of expected storage time, we recommend different approaches:

  1. Short Term Storage (one week or less): Store in Flow cell with water to prevent the probe from drying out.
  2. Intermediate Term (one week to one month): Store in cap, bottle, or beaker with water to keep membrane wet.
  3. Long Term (one month or longer): Remove Membrane Cap and store completely immersed in DI water or tap water if DI water is not available. Turn sensor upright and shake it to remove fill solution from inside the sensor.


A transmitter simply transmits a signal output only, such as 4-20mA signal. The transmitters Sensorex supplies are all 24V DC loop-powered with 4-20mA output.  Sensorex controllers are universally 100-240V AC powered and have 2 each 4-20mA outputs as well as 2 or more relay contacts.

Sensorex offers transmitters for all Sensors we manufacture and in some cases, have the 4-20mA transmitter interface is integrated into the sensor.

For pH and ORP: models TX100, TX2000 and TX3000 are offered.

For Conductivity: models CX100, CX2000 and CX3000 are offered for contacting conductivity sensors.  TCSMA and TCSTX transmitters are for use with inductive conductivity sensors model TCS3020.

For dissolved oxygen sensors: DO500 transmitter with display is offered or the DO6441 and DO6442 sensors are supplied with integrated transmitter circuit but no display.

Disinfection sensors including Sensorex FCL (free Chlorine) and CLD (chloride dioxide) are only available as blind sensors with 4-20mA output (No display).  A separate display can be integrated into the sensor loop or the display from the PLC or SCADA system can be used to display the sensor output.

No.  For transmitters, customers are required to supply their own power via a wall plug or 24V DC from a PLC.   For transmitter/controllers, customer are required to provide mains power.

All Sensorex transmitters and controllers are rated NEMA 4X (or IP65). This rating means that the devices are water-resistant.

Most transmitters and controllers are either wall or panel mountable.

Our TX2000RS and CX200RS pH/ORP and conductivity transmitters have Modbus 485 output.  No other digital outputs are available at this time.

For models CX2000 and CX3000, the temperature is output as a 2nd 4-20mA output.  The 4-20mA temperature range is preset to 0°C = 4mA and 100°C = 20mA, but this range can be adjusted in the settings of the unit.

For TX100 and CX100 transmitters, only English language menu is supported.  For TX2000, TX2000RS, CX2000, CX2000RS, TX3000 and CX3000, both English and simplified Chinese are supported.

Sensorex transmitter/controllers work with most manufacturers sensors.  The only exceptions are digital sensors with proprietary communication protocols or 5-wire differential sensors.


As of March 1, 2014, The SAM-1 will work on any Apple iOS phone or tablet running iOS 5.0 or higher.

Android is now supported as of April 10, 2015. Many Android devices are compatible. Supported Android devices must have:

  • Google Android 4.0 or higher (Modified versions of Android are not supported)
  • A 3.5mm headset jack with microphone (audio jack adaptors are not supported)
  • A screen size specified as Normal or Large (Small screen sizes are not supported)
  • Location services if GPS recording is desired
  • Access to Google Play

Please confirm that your Android device will meet these requirements with your phone carrier or device manufacturer.

October 19, 2017:

The SAM-1 app is not currently compatible with 64 bit iOS11. We are actively working to resolve the issue.

If you are using a protective case on your device, ensure that the case is not interfering with the connection of the SAM-1 to the audio jack.

SAM-1 uses the audio jack input of your device to communicate. Ensure that your audio jack volume set to maximum. Also ensure that the internal volume in your phone (Music setting) is not artificially set under 100%.

SAM-1 does have an internal re-chargeable battery. Connect it to your device, open the app, and ensure the device is charging. If the SAM-1 battery needs charging, the SAM-1 will trickle charge from the device and begin reading within a minute or two.**

Your device will normally keep the SAM-1 battery charged.**  An optional USB charging cable is available for keeping your SAM-1 fully charged if using the device extensively.

Please note: trickle charge functionality may not be compatible with Android devices.  Use of the SAMA-100 charging cable is recommended.

SAM-1 will support Smart Sensors from Sensorex. Currently you can choose the following sensors:

  • pH
  • pH and Temp
  • pH Spear tip
  • Conductivity and Temp


Additional measurement parameters are planned with future software updates.

SAM-1 currently supports English, German, French, Japanese, Russian, Spanish, Italian, and simplified Chinese. Other languages will be supported in future software updates. To use the SAM-1 in one of the languages listed above, your phone settings must be set to that language. The SAM-1 app and data files will display accordingly.

It is suggested to charge SAM-1 for 3 to 4 hours using the SAM-100 charging cable accessory.

Instructions for SAM-1 can be found in the SAM-1 App.  Download the App and then touch the “I” icon on the homepage for operating instructions.