A laboratory pH meter is a precision electrochemical instrument that measures the acidity or alkalinity of a liquid sample by detecting the concentration of hydrogen ions in solution. pH is expressed on a logarithmic scale from 0 to 14, where values below 7 indicate acidic conditions, 7 is neutral, and values above 7 are alkaline. Modern laboratory pH meters provide highly accurate, reproducible pH measurements and typically also measure oxidation-reduction potential (ORP), conductivity, dissolved oxygen, and temperature from a single instrument.
LabRepCo carries the Ohaus Starter series of laboratory pH meters – benchtop and portable models designed for research, analytical chemistry, environmental monitoring, biomedical applications, water quality testing, food and beverage analysis, and industrial quality control. The Ohaus Starter series combines precision measurement with an intuitive interface, offering entry-level to advanced models for every laboratory budget and complexity level. Browse by meter type below, or contact a LabRepCo specialist at 800-521-0754.
The most important decision when selecting a laboratory pH meter is whether you need a benchtop or portable model. Each configuration is optimized for a different working environment and workflow.
| Benchtop pH Meters | Portable pH Meters | |
| Form Factor | Plugged-in desktop unit with larger display and keypad | Battery-powered handheld unit for field and mobile use |
| Best For | Laboratory bench use where samples are brought to the meter; regulated environments requiring data logging and GLP output | Field measurements, remote sampling locations, production floors, or any application where the meter must come to the sample |
| Display | Larger screen with more simultaneous parameter display | Compact display; typically shows pH and temperature simultaneously |
| Data Output | USB, RS232, or Bluetooth data transfer for LIMS and GLP documentation | Limited connectivity; basic data logging on advanced models |
| Calibration | Multi-point calibration (up to 5 points) for higher accuracy | Typically 1 to 3 point calibration |
| Ohaus Models | Starter ST2100, ST3100, AB23PH, AB33PH, AB33M1 series | Starter ST300, ST300-B, ST300-G series |
ORP (oxidation-reduction potential), also called redox potential, measures a solution’s ability to oxidize or reduce other substances. It is expressed in millivolts (mV) and is an important parameter in water treatment, aquaculture, swimming pool monitoring, food processing sanitation, and certain research applications. Most Ohaus Starter series pH meters include ORP measurement capability alongside standard pH measurement, making them multi-parameter instruments rather than pH-only devices.
If your application requires ORP measurement, confirm that the specific Ohaus Starter model you select includes an ORP electrode input. Most benchtop Starter models support ORP as standard; contact LabRepCo to verify compatibility for your specific workflow.
The glass combination electrode is the most important consumable component of any pH meter system. Over time, the reference junction can become clogged, the glass membrane can become scratched or contaminated, and electrode response time slows – all indicators that a replacement electrode is needed. LabRepCo carries Ohaus Starter series replacement electrodes and accessories, including combination pH-reference electrodes, ORP electrodes, and conductivity cells.
Proper electrode storage and maintenance is critical to measurement accuracy. Always store combination electrodes in electrode storage solution (not distilled water), rinse with deionized water between samples, and calibrate before each use session. Browse our Starter Electrodes for pH Measurement for compatible replacement electrodes.
A benchtop pH meter is a plugged-in desktop instrument designed for laboratory bench use, offering larger displays, multi-point calibration, and data output via USB or RS232 for GLP documentation. A portable pH meter is battery-powered and handheld, designed for field sampling, production floors, or any application where the instrument must be brought to the sample rather than the sample brought to the instrument. For laboratory use with regulated documentation requirements, a benchtop model is typically the right choice. For field or mobile applications, a portable model is preferred.
pH meters should be calibrated before each use session using fresh buffer solutions. At minimum, a two-point calibration using pH 4.0 and pH 7.0 buffers covers most laboratory applications. Three-point calibration adding pH 10.0 is recommended when measuring samples at the extremes of the pH range. In regulated pharmaceutical and GMP environments, calibration records must be maintained as part of GLP documentation. The Ohaus Starter series benchtop meters support up to five-point calibration for maximum accuracy across the full pH range.
ORP (oxidation-reduction potential) measures a solution’s tendency to gain or lose electrons in chemical reactions, expressed in millivolts. It is distinct from pH – a solution can be neutral in pH but highly oxidizing or reducing. ORP is an important parameter in water treatment (chlorination monitoring), aquaculture, swimming pool and spa management, food processing sanitation verification, and research applications studying redox chemistry. Most Ohaus Starter series meters support ORP measurement alongside pH.
Key indicators that a pH electrode needs replacement include slow response time (taking more than 30 seconds to stabilize), inability to calibrate to within acceptable tolerance using fresh buffers, readings that drift continuously rather than stabilizing, visible damage to the glass bulb or reference junction, or the electrode having been stored dry for an extended period. Most glass combination electrodes have a service life of 1 to 2 years under normal use conditions. LabRepCo carries Ohaus Starter series replacement electrodes compatible with all Starter series meters.
LabRepCo carries the Ohaus Starter series of laboratory pH meters, including benchtop models (ST2100, ST3100, AB23PH, AB33PH, AB33M1 series) and portable models (ST300 series), plus compatible Starter series replacement electrodes. All Ohaus Starter series meters are available with full manufacturer warranty through LabRepCo’s GSA and E&I cooperative purchasing contracts.
Browse our benchtop pH meters and portable pH meters, or contact LabRepCo’s instrument specialists at 800-521-0754 for guidance on selecting the right Ohaus Starter model for your application.
Submit a PO
Looking to submit a purchase order rather than buying online? Click on the Submit a PO button to learn more.
Sales & Support
Customer Service
Mon - Fri: 8AM to 5PM ET
101 Witmer Road, Suite 700
Horsham, PA 19044
Would you like us to get in touch with you? Fill out the form below and we will contact you.
