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pHionics 4-20 mA STs Series pH Sensor/Transmitter

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The pHionics STs Series™ pH sensor/transmitter provides highly accurate pH measurement from 0-14 pH. The electrode is glass with a silver/silver chloride reference wire and double junctions to ensure long-term stability in harsh chemical solutions.

Part Number: STS1014S-025

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$1,883.00 ex GST

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Overview
Specifications
FAQ's
Video's

All STs Series base prices include a 7.6m (25ft) cable.

Product Description

In addition, the body is made from Delrin and 316 Stainless Steel which provide excellent chemical resistance and durability for many years of service. Finally, input/output isolation, combined with differential amplification, virtually eliminates any forms of interference. From monitoring groundwater pH for contamination to industrial process control, the STs Series pH sensor/transmitter provides high value for long-term water quality applications.

Noise Reduction

From crystal-clear streams only touched by radio frequencies to wastewater treatment plants surrounded by heavy machinery, background noise and interference is everywhere. Our signal conditioning removes background (common-mode) noise from the measurement to ensure high accuracy. The signal is also sent through a preamplifier to strengthen it before traveling through a twisted-pair, shielded cable that protects the amplified 4-20 mA signal until it reaches the datalogger or controller.

Ease-Of-Use

Typical 2-wire transmitters are relatively easy to set up but improper wiring can result in damage to the transmitter or expensive controller. The STs Series prevents damage with a reversible input protection so the two wires per parameter can be switched without performance issues. Additionally, all parts, cable included, are quick and easy to replace without any special tools. This cuts down on maintenance time and costs, especially in circumstances where cable damage otherwise requires complete replacement of traditional sensors and transmitters.

Isolation

Isolation removes ground loop interference to save troubleshooting time and money by preventing damage to connected electronics in the case of power surges up to 600V. This allows the STs Series to be used in process control applications without worrying about different grounding potentials of the solution or mounting surface. It has the added benefit of protecting connected devices and people if exposed to large amounts of current caused by damaged machinery or improper wiring.

Low Power Usage

Sensors and transmitters made by other competitors commonly use more current than the 4-20 mA signal to power their devices, ranging from 3-15 mA additional. pHionics only ever uses the amount of current required for the signal, allowing STs Series devices to function between 60% to 375% longer on the same battery. The STs Series also only requires 8 VDC and has a three second turn-on time, further reducing power usage.

2-wire, 4-20 mA pH Sensor/Transmitter

Output	4-20 mA
pH Range	0-14 pH
Operational Temperature Range	0-70°C
Electrode Type	Silver/Silver chloride, double junction, replaceable gel electrode
Automatic Temperature Compensation	0-50°C
Isolation	600 VDC
Power Supply Voltage	8-40 VDC
Loop Impedance (Max)	200 Ohms at 12 VDC 800 Ohms at 24 VDC 1600 Ohms at 40 VDC
Response time	95% < 5 seconds
Pressure Range	0-100 psi
Wetted Materials	316 SS, Delrin, Viton, glass
Length	13.5 in (34.3 cm)
Width	0.750 in (1.9 cm) maximum
Weight (No cable)	0.50 lbs (0.227 kg)
Linearity	±0.004 pH
Accuracy	±0.014 pH
Sensitivity	±0.01 pH
Stability	±0.03 pH per year
Repeatability	±0.01 pH

2-wire, 4-20 mA Temperature Sensor/Transmitter

Output	4-20 mA
Temperature Range	0-50°C
Power Supply Voltage	7-40 VDC
Loop Impedance (Max)	250 Ohms at 12 VDC 850 Ohms at 24 VDC 1650 Ohms at 40 VDC
Isolation	600 VDC

Cable

Cable Material	Polyurethane
Type	4 conductor, Kevlar reinforced, water blocked, shielded, twisted-pair wiring
Maximum Distance	3 miles
Replaceable?	Yes

STs Series pH FAQ

How should the electrode be stored?

pH electrodes must be stored in solution to avoid drying out the glass bulb. We recommend storage in 3.0M potassium chloride (KCl) solution for maximum lifespan. Do not store in deionized water or other low ionic solution as this significantly reduces lifespan of the electrode.

How long does the electrode last?

Typical electrode life in an innocuous application is about three years. The nature of the solution being measured (flow rate, pH range, ion concentration etc.) all affect longevity so the lifespan can range from 6 months to 5 years. Electrode life must be determined empirically for each application through consistent calibration.

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, excluding 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.

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 for more information.

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?

Our pH electrodes are silver/silver chloride with a Teflon double junction. They are replaceable with a gel electrolyte instead of refillable electrolyte solution to reduce overall maintenance time.

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 the measurement or process is not significantly disrupted. At a minimum, a spare electrode is recommended in the event of damage–or the need for eventual replacement–when waiting for a replacement to be shipped could be detrimental to your application.

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

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. Check out our pH Electrode Care Guide for cleaning and troubleshooting procedures.

STs Series Initial Setup

pHionics STs Series Setup with HOBO RX3000

STs Series Electrode Replacement

STs Series Cable Replacement