Conductivity and Dissolved Oxygen Meters Lab Equipment Manufacturer, Supplier and Exporter in India

Ten meters are listed here, CDOM-0001 to CDOM-0010: six conductivity meters in pocket, portable and bench forms, and four dissolved oxygen meters. With both measurements the meter is the easy part of the decision. For conductivity, the cell constant of the probe and how the meter handles temperature decide whether a reading means anything. For dissolved oxygen, the sensor technology decides what the running cost is and whether a still sample can be measured at all. Those two points are below.

Conductivity: temperature compensation is not an optional feature

The conductivity of a solution changes by roughly two per cent for every degree Celsius, which means a conductivity figure without a temperature attached to it is not a measurement. Three of the codes here signal how they handle that, one as automatic temperature compensation, one as a manual table model and one as automatic, so the distinction exists in the range and is worth understanding before choosing:

• Automatic compensation measures the sample temperature and corrects the reading to a reference temperature, normally twenty-five degrees Celsius. This is what you want for routine work, and it is what makes two readings taken on different days comparable.
• Manual compensation requires the operator to enter the temperature, which is fine in a controlled laboratory and a source of error everywhere else.
• Ask the reference temperature and the compensation coefficient, and whether the coefficient can be changed. The standard coefficient suits dilute salt solutions; it does not suit strong acids, sugar solutions or pure water, so if your samples are unusual, an adjustable coefficient matters. Ask also whether the meter can report uncompensated conductivity, which some standard methods require.

The cell constant: the most common mis-purchase

A conductivity probe has a cell constant, and the cell has to match the range you are measuring. A cell of low constant suits pure and distilled water; a cell of around one suits ordinary water, effluent and most laboratory solutions; a cell of high constant suits concentrated solutions and brines. Fit the wrong one and the reading is noisy, slow or simply wrong at the end of the range you care about. So ask, for every code: which cell is supplied and its constant; the measuring range that follows from it; whether other cells are available and at what price; and whether the meter recognises the cell constant automatically or it must be entered.

Then ask about calibration, which conductivity meters need regularly: which standard solutions are recommended, whether any are supplied, their shelf life once opened, and whether a one-point or multi-point calibration is used. A meter supplied without standards cannot be put into service on the day it arrives. For the electrode itself, ask the body material, how it should be stored, and whether it is a platinised cell, because platinised surfaces must not be wiped and eventually need replatinising, which is a service operation rather than a cleaning one.

If you intend to use the meter for total dissolved solids, note that a TDS reading from a conductivity meter is a calculation, not a measurement: the instrument multiplies conductivity by a factor that depends on which salts are present. Ask what factor the meter uses and whether it can be changed, and treat the figure as an estimate unless your samples match the assumption behind the factor.

Dissolved oxygen: ask which sensor, because it decides everything else

Two technologies are in common use and the listing does not say which these four are, so ask.

A membrane-covered electrochemical sensor is the traditional and cheaper arrangement. It consumes oxygen as it measures, which has a consequence that catches people out: the sample has to flow past the membrane, so a reading taken in a still sample reads progressively low and either the probe must be stirred, moved, or fitted with a stirrer. These sensors also need their membrane and electrolyte replaced periodically, they drift between calibrations, and the membrane is damaged easily.

An optical or luminescent sensor does not consume oxygen, so it needs no stirring, has no membrane or electrolyte to replace, holds its calibration longer and survives rougher handling. It costs more to buy and the sensing cap is a periodic replacement. For a teaching laboratory that measures occasionally, or a field programme where consumables are hard to get, it is usually the cheaper option over five years.

Whichever it is, ask: the calibration procedure, which for dissolved oxygen is normally a single point in water-saturated air with a zero check in sodium sulfite, and whether a calibration sleeve is supplied; whether the meter corrects for temperature, barometric pressure and salinity, since the saturation value depends on all three, and whether the pressure is measured by the instrument or has to be entered; and the consumable list with prices and shelf life, which for a membrane sensor is the real running cost. If the meter is for biochemical oxygen demand work, ask specifically for a probe that fits a BOD bottle and has its own stirrer, because a standard probe will not do that job.

Form factor and the practical details

The range runs from a pocket meter to microprocessor-based bench instruments, and the choice follows the use rather than the price. For field work ask the ingress protection rating, the battery type and life, and whether readings can be logged and downloaded. For bench work ask the display, whether there is a stand or electrode holder, the output or interface if results must be recorded, and the mains supply. For every code ask the resolution and the accuracy figure, with the conditions it holds under, the cable length on the probe, and the warranty position on probes, which are usually excluded or shortened and are the expensive part.

Also worth confirming

Two codes in this listing, CDOM-0008 and CDOM-0009, carry the same name as each other, so ask what separates them before ordering either. Ask also for the manual, the quantity of standards and consumables to order with the instrument, the supply voltage, frequency and plug type for your country, the calibration and service arrangement locally, and whether a calibration certificate is supplied. Any accuracy or range figure quoted is confirmed in writing on the quotation; ask for the conditions behind it.

Related ranges on this site

Flame photometry and colorimetric determinations are under TDS Meter, Photocolorimeter and Flame Photometer. The distilled or deionised water these calibrations and dilutions need is under Water Distillations and Stills. Nitrogen and chemical oxygen demand determinations are under Kjeldahl Digestion and Distillation Unit, weighing under Lab Balances and Scales, and sterilisation and shaking under Autoclaves, Sterilizers and Shakers.

Request a quote

Say what you are measuring and over what range, and ask for the probe specification rather than the meter alone. For example a bench conductivity meter with automatic temperature compensation (CDOM-0005) with a cell of the constant suited to your samples, calibration standards included, and the coefficient adjustability stated; and a dissolved oxygen meter with the sensor type named, the correction set confirmed and the consumable prices listed. Contact Ray Export for specifications, prices and lead times.

Frequently asked questions

Which conductivity cell constant do I need?

Match the cell to the range you measure. A cell of low constant suits pure and distilled water; a cell of around one suits ordinary water, effluent and most laboratory solutions; a cell of high constant suits concentrated solutions and brines. The wrong one gives a noisy, slow or simply wrong reading at the end of the range you care about. For every code, ask which cell is supplied and its constant, the measuring range that follows, whether other cells are available, and whether the meter recognises the constant automatically.

Is automatic temperature compensation necessary?

For routine work, yes. Conductivity changes by roughly two per cent per degree Celsius, so a figure without a temperature is not a measurement. Automatic compensation measures the sample temperature and corrects to a reference, normally 25 deg C, which makes readings taken on different days comparable; manual compensation needs the operator to enter the temperature. Ask the reference temperature and the coefficient, and whether the coefficient can be changed, since the standard one does not suit strong acids, sugar solutions or pure water.

Can the conductivity meter give a TDS figure?

It can display one, but a TDS reading from a conductivity meter is a calculation, not a measurement: the instrument multiplies conductivity by a factor that depends on which salts are present. Ask what factor the meter uses and whether it can be changed, and treat the result as an estimate unless your samples match the assumption behind that factor. Ask also whether the meter can report uncompensated conductivity, which some standard methods require, and whether the electrode is a platinised cell, which must not be wiped.

Which dissolved oxygen sensor should we choose?

The listing does not say which technology the four DO meters use, so ask. A membrane-covered electrochemical sensor consumes oxygen as it measures, so a still sample reads progressively low unless the probe is stirred or moved; its membrane and electrolyte need periodic replacement, and it drifts between calibrations. An optical or luminescent sensor consumes no oxygen, needs no stirring, has no membrane or electrolyte, holds its calibration longer and tolerates rougher handling, though its sensing cap is a periodic replacement.

How are these meters calibrated?

Conductivity meters need regular calibration with standard solutions: ask which are recommended, whether any are supplied, their shelf life once opened, and whether one-point or multi-point calibration is used, because a meter delivered without standards cannot go into service on the day it arrives. Dissolved oxygen is normally calibrated at a single point in water-saturated air with a zero check in sodium sulfite; ask whether a calibration sleeve is supplied, and whether the meter corrects for temperature, barometric pressure and salinity.

Pocket, portable or bench meter - how do we choose?

Choose by use. For field work, ask the ingress protection rating, battery type and life, and whether readings can be logged and downloaded. For bench work, ask about the display, the stand or electrode holder, the output or interface if results must be recorded, and the mains supply. For every code, ask the resolution and the accuracy figure with its conditions, the probe cable length, and the warranty on probes. For BOD work, ask specifically for a probe that fits a BOD bottle and has its own stirrer.

Key takeaways

• Cell constant first: match the conductivity cell to your range, or the reading fails where it matters most.
• Temperature makes it a measurement: automatic compensation to a stated reference keeps readings comparable.
• TDS is a calculation: ask the conversion factor and treat the figure as an estimate.
• Name the DO sensor: membrane sensors need stirring and consumables; optical sensors do not.
• Standards on day one: order calibration solutions with the meter so it can enter service on arrival.
• Same name, two codes: ask what separates CDOM-0008 from CDOM-0009 before ordering either.

About this page

Ray Export is a manufacturer and exporter of laboratory, scientific and educational equipment based at Plot No. 449, HSIIDC Industrial Area, Saha, Ambala, Haryana 133104, India. Enquiries: [email protected], +91-9817319615.

Written by Palak Mall, Senior Content Writer. Technically reviewed by Arvind Kumar, Lab Equipment Specialist, 12+ years in laboratory and testing instrumentation. Last updated: 18 October 2026.

Specifications for every code, including cell constant, measuring range, resolution, accuracy conditions and sensor type, are confirmed in writing on the quotation. For calibration or other certificates, contact us for the latest copies of the relevant certificates. No price is quoted on this page. Listing notes: CDOM-0008 and CDOM-0009 carry the same name; the listing does not identify which codes are conductivity meters and which are dissolved oxygen meters, nor the sensor technology of any dissolved oxygen meter.