STs Series Conductivity FAQ

Answers to common questions regarding STs Series Conductivity care, features, and recommendations

How should the electrode be stored?

The electrode should be stored dry with the electrode guard on for protection.  Before storage, rinse the electrode and interior of the conductivity guard to remove debris.  A soft brush can also be used to for any debris that remains stuck on the electrode.

How long does the electrode last?

Our conductivity electrode is exceptionally durable and can last between 5 and 20 years assuming proper care and use in an application that will not attack the electrode cells.  See our guide on Conductivity Electrode Care for more information.

Is the output automatically temperature-compensated (ATC)?

The output is adjusted by 2% per °C relative to 25°C.  A thermistor within the housing is used which is why the ATC is most accurate when the device is fully submersed.  ATC functions regardless of whether the temperature output is in use.

Do you provide a warranty?

Yes, our products come with a 2-year warranty but normally the electrode is excluded. For STs Series Conductivity electrodes, we also extend the two year warranty to the electrode.  These products are designed to last far longer if properly cared for and we will do what we can to help if any problems occur in or out of warranty.  Please don’t hesitate to reach out!

Read our full warranty here.

What voltage is required for the STs Series Conductivity?

An 8VDC power supply is sufficient with standard lengths of cable.  Voltage drop must be accounted for over long lengths of cable (50+ ft.) to ensure enough power is supplied to any water quality sensor.  To calculate it, first double the length of cable to get the account for the full length of the circuit, then multiply that by resistance per foot/meter to get total resistance.  pHionics uses 24 AWG tinned-copper wire which has a resistance of 0.026 ohms per foot (0.084 ohms per meter).  Multiply total resistance by the maximum expected current (20 mA, or 0.02 A, is safest) to obtain expected voltage drop.  Verify that the voltage drop plus required voltage for pHionics sensors (8 VDC) is less than the power supply voltage.  Please visit our article on voltage drop for more information and example calculations.

How long are STs Series devices expected to last?

While the electrode will require replacement every three years on average, the housing, seals, and cables are intended to last 10-20 years with proper care. To increase longevity of the seals, the Viton O-rings should be relubricated with a silicon grease during each disassembly, or at least inspected for any debris or damage.  The harshness of the solution (high/low pH, extreme salinity, high pressure, etc.) also affects longevity, which is why we offer the option of 316 Stainless-steel or titanium for the metal housing and PVDF (standard) or Delrin for the plastic.  All parts are replaceable to save money and limit waste in the event that any piece gets damaged.

What type of electrode is provided?

pHionics conductivity electrodes use a four-cell technique for high accuracy.  The electrodes are made of Delrin and the cells out of 316 stainless steel or titanium.  The electrode guard should always be on during measurement because it provides greater accuracy.

What spare parts are recommended?

For critical measurements, a duplicate STs Series combined sensor/transmitter is always recommended so a replacement for every part is available at any time.  A duplicate simplifies troubleshooting by always having a functional STs Series available.  It also allows for swapping of devices during calibration and cleaning, so measurement is not significantly disrupted.  At a minimum, a spare electrode is recommended in the event of damage or eventual replacement. 

How often should the STs Series Conductivity be cleaned and/or calibrated?

The frequency of calibration must be determined empirically as rate of drift and debris accumulation differs for each application. Calculating the offset during calibration provides information on whether the electrode is still viable.  See our article on Proper Sensor Calibration for assistance in the process.

How can the STs Series be installed/mounted?

The STs Series can be mounted in-line using the optional 1.0″ NTP PVDF DIN Connector, immersed with compression fitting in a 3/4″ pipe, or freely suspended by the Kevlar™ cable.  Please see the pHionics STs Series Device Manual or contact us at [email protected] for more information.

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