Horiba LAQUAtwin pH-33 Pocket pH Meter, 0.01 pH, 5-Point

LAQUAtwin-pH-33 is the top model of the three-member LAQUAtwin pH family from HORIBA Advanced Techno: a 164 mm pocket meter with a replaceable flat glass sensor that reads pH from a sample as small as 0.1 mL, resolves 0.01 pH and accepts up to five calibration points.

A pH meter you can calibrate and read from a single drop

The measuring surface is a flat glass membrane with a liquid junction, set into the sensor that clips onto the meter body. A few drops placed on the flat sensor and covered by the light shield cover are enough, and the manual states a minimum of 0.1 mL, or 0.05 mL when the optional sampling sheet B is used. That suits spot checks where a bench meter and electrode stand are not realistic.

Within the family the pH-33 is the one with the finest resolution (0.01 pH, against 0.1 pH on the pH-11) and the only one that shows temperature on its display (0 °C to 50.0 °C). It also has the deepest calibration, up to five points.

What the manual lists for this meter

• Glass electrode method, 0 to 14 pH range, 0.01 pH resolution and 0.01 pH stated accuracy.
• Up to 5-point calibration with USA or NIST buffer sets selectable in setup mode.
• Auto stable (AS) mode by default, with a stability icon, or auto hold (AH) mode that freezes the reading until MEAS is pressed.
• Display cycles between pH, voltage and temperature in AS mode; custom monochrome LCD with backlight.
• IP67 housing (no failure after 30 minutes at 1 m depth) but, as the manual notes, not for use underwater.

Technical specification

Measurement and meter data

Operating and physical data

Package contents and consumables

Choosing between pH-11, pH-22 and pH-33

The three models share one body and one S010 sensor, so the choice is about resolution and calibration depth. If a reading to 0.1 pH is enough for a quick pass/fail, the pH-11 does it. If you work to a tolerance of a few hundredths of a pH, or if you need to document a multi-buffer calibration, the pH-33 is the model to quote; it is also the only one that can show temperature and lets you adjust the temperature sensor against a reference thermometer.

For samples of unknown pH the manual recommends three-point calibration with pH 4.01, 7.00 (or 6.86) and 10 (or 9.18). When the sample is known, choose standards close to its pH.

First use, calibration and care

Insert two CR2032 cells with the plus sides up, slide the sensor on until catch A seats in hole a, and check the waterproof gasket is clean and not twisted. Before the first use, or after several days without use, condition the sensor: put a few drops of pH 7 standard on the flat sensor and wait a few hours, then rinse with running water. Calibrate afterwards, rinsing the sensor with the standard first to reduce carry-over.

After each measurement clean the sensor with tap water, dab it dry with a soft tissue and close the light shield cover. If calibration shows Er4, repeat conditioning and check the standard; repeated failure means the sensor has deteriorated and should be replaced. Initialise calibration data after fitting a new sensor.

Where a pocket pH meter earns its place

Typical uses in the Gulf are field and workshop checks where water chemistry matters: boiler and cooling-tower make-up, wash-down and cleaning solutions, effluent screening before a lab test, and food or agricultural samples. The manual limits sample and meter to 5 °C to 40 °C and warns that a large gap between sample and ambient temperature increases the error, so let hot samples settle first.

Related items

Sensor S010, the pH 4.01 and 7.00 standards and sampling sheet B are listed above by part number.

Related Horiba products: Horiba LAQUAtwin Salt-22 Pocket Salinity Meter, 0.01 to 25 %, Horiba LAQUAtwin 4EC-33 Pocket Conductivity and TDS Meter, Horiba LAQUA TB220-K Portable Turbidity Meter Kit, ISO 7027, Horiba LAQUA PH220 Handheld pH/ORP/Temperature Meter, Horiba LAQUA WQ-330-K 3-Channel Handheld Water Quality Meter and Horiba LAQUA DO220 Handheld Dissolved Oxygen Meter, Galvanic.

Documents and quotation

The official Horiba instruction manual for LAQUAtwin-pH-33 is hosted on this page for download. Seven Star LLC is an independent supplier in Muscat; send your quantity and delivery location through the quotation form and we will quote this item. Please confirm the exact order code, ratings and approvals against the document before ordering. More related products: product category.