Electrodes for Swimming Pools

These four electrodes can be ordered directly

We stock the most requested versions for pools and spas. They can be ordered from our shop, with either a 1 m or 2 m cable.

All prices in euros, including VAT, plus shipping.

What an electrode for pool water needs to deliver

An electrode consists of a glass membrane, a diaphragm, inner and outer reference electrolyte, and a reference electrode. All four components in Apera’s pool electrodes are designed for chlorine exposure, continuous operation, and changing water quality. This results in three key figures that make the difference in everyday use:

• Fast response: 95% of the reading is reached after 10 seconds at 25 °C.
• High accuracy: the factory slope of the pH electrode is 97%.
• Low drift: long-term stability is under 10 mV, equivalent to 0.15 pH.

Robust glass membrane

The glass membrane detects the activity of hydrogen ions (H⁺) in the water and is the core technology of every electrode. The membrane in Apera’s pool electrodes is 10 times more robust than conventional glass membranes and combines low impedance with high stability. This makes it suitable for continuous monitoring in pools and spas.

Double diaphragm instead of simple ceramic

A single ceramic diaphragm lets the electrolyte leak out slowly and evenly, but it’s prone to fouling and clogging. That’s why the pool electrodes mostly use a double electrolyte structure, which significantly reduces this risk. This is reflected in the product name as “Double Junction.”

Long-lasting reference without silver ions

To keep the reference electrode stable over the long term, the reference electrolyte contains no silver ions. This avoids reactions with sulfides or proteins in the sample solution, which would otherwise clog the diaphragm.

Macromolecule coating for stable redox readings

Platinum and gold surfaces develop a thin oxide layer during storage and use and become contaminated, which changes the measurement interface. Apera’s macromolecule coating shields them from the environment: the electrode responds significantly faster, readings are largely stable after about 2 minutes, and different ORP electrodes deliver much more consistent values.

• Chemically resistant, releases no particles or breakdown products into the medium.
• Heat-resistant up to 190 °C.
• High ion conductivity and pronounced proton-exchange function.
• Selectively permeable — after water uptake, only hydrogen ions pass through.

pH electrodes for pool water

Two series cover the pool segment. The 201DJ and 203DJ series in a polycarbonate housing is the standard for pools and spas. The IndSen 710 series in lead-free glass is designed for higher temperatures up to 100 °C and more demanding installations.

201DJ and 203DJ series

Available versions: 201DJ-C (BNC, 12 × 120 mm), 201DJ-CBS (BNC, 12 × 83 mm), 201DJ-S7 (S7), 203DJ-C (BNC), and 203DJ-F (BNC+RCA). The 201DJ-C is available in the shop; the other versions are available on request.

Feature	201DJ series	203DJ series
Measuring range	0 to 14 pH	0 to 14 pH
Temperature	0 to 80 °C	0 to 80 °C
Housing material	PC (polycarbonate)	PC (polycarbonate)
Diaphragm	Double diaphragm: ceramic / foam plastic	Double diaphragm: ceramic / ceramic
Reference	Ag/AgCl	Long-life reference
Electrolyte	Gel without AgCl or AgCl-saturated gel	Gel I and gel without AgCl
Temperature sensor	not available	203DJ-C: no, 203DJ-F: optional
Dimensions	12 × 120 mm, 201DJ-CBS: 12 × 83 mm	12 × 120 mm
Connector	BNC, 201DJ-S7: S7	BNC, 203DJ-F: BNC+RCA

IndSen 710 series

pH electrodes made of lead-free glass with a ceramic/ceramic double diaphragm and long-life reference, usable up to 100 °C. This series is fully available on request.

Feature	IndSen 711	IndSen 712	IndSen 714	IndSen 716
Measuring range	0 to 14 pH
Temperature	0 to 100 °C
Housing material	Lead-free glass
Diaphragm	Double diaphragm: ceramic / ceramic
Reference	Long-life reference
Electrolyte	Gel I and gel without AgCl
Temperature sensor	optional	no	optional	no
Connector	BNC	S7	PG13.5 / BNC	S8
Dimensions	12 × 120 mm

ORP electrodes for disinfection control

The redox potential shows how effectively the disinfectant is working in the pool. Depending on the application, platinum or gold sensors are used, as a pin, film, or ring.

Type	Design	Measuring range	Temperature range	Application
Platinum	Pin, film, or ring	±2000 mV	-10 to 135 °C	Chromate reduction, nitrite oxidation, disinfection of pool and drinking water
Gold	Pin, film, or ring	±2000 mV	-10 to 135 °C	Cyanide oxidation, water disinfection

301DJ, 303DJ, and 306DJ series

Available versions: 301DJ-C (platinum pin), 301DJ-CS (platinum pin, 12 × 83 mm), 303DJ-C (platinum film), 303DJ-C-G (gold film), and 306DJ-C-G (gold ring). The 301DJ-C is available in the shop; the other versions are available on request.

Feature	301DJ series	303DJ series	306DJ series
Measuring range	±2000 mV	±2000 mV	±2000 mV
Temperature	0 to 80 °C	0 to 80 °C	0 to 80 °C
Housing material	PC (polycarbonate)	PC (polycarbonate)	PC (polycarbonate)
Diaphragm	Double diaphragm: ceramic / foam plastic	Double diaphragm: ceramic / ceramic	Double diaphragm: ceramic / ceramic
Reference	Ag/AgCl	Long-life reference	Long-life reference
Electrolyte	Gel without AgCl or AgCl-saturated gel	Gel I and gel without AgCl	Gel I and gel without AgCl
Sensor	Platinum pin or gold pin	Platinum film or gold film	Platinum ring or gold ring
Dimensions	12 × 120 mm, 301DJ-CS: 12 × 83 mm	12 × 120 mm	12 × 120 mm
Connector	BNC	BNC	BNC

IndSen 3710 series

ORP electrodes made of lead-free glass with a platinum or gold ring, usable up to 100 °C. This series is fully available on request.

Feature	IndSen 3711	IndSen 3712	IndSen 3714	IndSen 3716
Measuring range	±2000 mV
Temperature	0 to 100 °C
Housing material	Lead-free glass
Diaphragm	Double diaphragm: ceramic / ceramic
Reference	Long-life reference
Electrolyte	Gel I and gel without AgCl
Sensor	Platinum ring or gold ring
Connector	BNC	S7	PG13.5 / BNC	S8
Dimensions	12 × 120 mm

Calibration, standard, and storage solutions

Regular calibration and proper storage keep an electrode accurate for years. The right solutions can be purchased directly from our shop; they are available in 250 ml bottles.

• pH calibration buffers: pH 4.00, pH 7.00, and pH 10.01, 250 ml each.
• ORP standard solutions: 222 mV, 470 mV, and 650 mV, 250 ml each.
• Storage solution: 3M KCl for pH and ORP electrodes, 250 ml.

You’ll find the available calibration, standard, and storage solutions in our shop.

Which connector fits your meter?

The electrodes are available with the standard connectors used in pool technology. If you’re not sure which connector your system uses, simply send us a photo of the socket along with your inquiry.

Connector	Description
BNC	Standard connector on most measuring and control devices
S7	Screw head, common on dosing systems
S7-BNC cable	Connecting cable from S7 head to BNC
BNC + RCA	Additional RCA contact for the temperature sensor
PG13.5 / BNC	PG13.5 process thread with BNC signal connector
S8	Screwed head for fixed installations