Sensor Type

pH: Series Q25P Differential or Conventional types

ORP: Series Q25R Differential or Conventional types

Display Range

pH: 0.00 - 14.00 ORP: -1000 to +2000 mv

Accuracy

0.02 pH or 2 mv

Repeatability

0.01 pH or 1 mv

Sensitivity

0.01 pH or 1 mv

Analog Output

2-Wire unit: Single 4-20 mA DC, 450 ohms maximum

Battery unit: Two 0-2.5 VDC, 50K ohms minimum

External DC: Two 0-2.5 VDC, 50K ohms minimum

Power Requirements  

2-Wire unit: 17-30 VDC, 25 mA maximum

Battery unit: 2 AA Alkaline batteries

External DC: 5-17 VDC, 10 mA maximum

Output Isolation

600 V Galvanic isolation

Enclosure

NEMA 4X (IP-66) Polycarbonate, V-0 flammability

Weight

2-Wire of External DC Unit: 1lb. (0.45 Kg) 
Battery Unit: 2 lbs. (0.9 Kg)

Certifications

CE marked to BS EN 61326-1:2006 Standard 
UL and CSA General Purpose

Size

4.4”H x 4.4”W x 3.5”D (111 x 111 x 90 mm)

Mounting Options

Wall or pipe mounting bracket supplied

Conduit Entry

Two PG-9 cord grips, 0.16-0.31” diameter cable

Ambient Temperature

Operating: -40° to + 60°C 
Storage: -40° to + 70°C

Ambient Humidity

0-95%, Non-condensing

Conventional Sensor

The most widely used pH sensors contain a hydrogen ion sensitive glass measuring electrode and a silver/silver chloride reference element. The reference element is sealed in the sensor which is filled with an electrolyte and electrically connected to the outside solution through porous junctions. The glass electrode is in direct contact with measured solution.

Conventional sensors are good for clean water applications and typically have an operating life of 1-3 years. They are relatively inexpensive and are available in submersible or inline versions.

Differential Sensor

Differential sensors have a pH sensitive glass electrode (identical to the measuring electrode) rather than the silver/silver chloride element of conventional sensors. The second glass electrode is housed in a chamber filled with pH 7 buffer. A high surface area junction connects the buffer system to the pH measuring element. The pH is then measured by calculating the voltage difference between the two glass electrodes.

Differential sensors are the best option for demanding applications like wastewater, plating baths, industrial process water, or high temperature applications. They are also good in applications containing sulfur as sulfur compounds destroy the silver/silver chloride component of conventional sensors. Differential sensors are much longer lasting.