Ohmmeters – find manufacturers and suppliers

Ohmmeters are electrical measuring devices for determining the electrical resistance of a conductor, component or circuit.

Resistance is measured in ohms (Ω) and is a fundamental parameter in electrical engineering, as it indicates how strongly a material or component inhibits the flow of electrical current. The higher the resistance, the worse an object conducts electricity.

Below is an overview of how ohmmeters work, the types and measuring methods of ohmmeters, their use and areas of application, as well as precautions to be taken when operating them:

How ohmmeters work:

Ohmmeters work according to a simple physical principle: Ohm's law (U = R × I).
To measure the resistance, the device applies a defined voltage to the object to be measured and measures the current flowing through it.
The resistance is calculated from the ratio of voltage to current.

There are two basic types of ohmmeters:

1. Analog ohmmeters: Usually work with an internal voltage source e.g. battery and a pointer measuring mechanism. The current flow through the measured object moves the pointer, which indicates the resistance on a scale.
2. Digital ohmmeters usually as part of a multimeter: Use microcontrollers and A/D converters to measure voltage and current with high precision and display the resistance mathematically.

Measuring methods of ohmmeters:

Different measurement methods are used depending on the area of application and the required accuracy:

1. Two-wire measurement: The simplest form, in which current and voltage are conducted via the same two wires. Suitable for low resistance values, but susceptible to measurement errors due to cable lengths and contact resistances.
2. Four-wire measurement (Kelvin measurement): Separate leads for current supply and voltage measurement to eliminate errors due to contact resistance. Particularly precise and common for measurements of very small resistances (<1 Ω).
3. Bridge measurement method: A Wheatstone bridge or other comparator circuit is often used for precise laboratory ohmmeters.

Use and application areas of ohmmeters:

Ohmmeters are used in many areas of electrical engineering and electronics - both in development and in operation, maintenance and fault diagnosis. The most important applications include:

1. Testing of resistors:
Verification of the nominal value for electronic components.

2. Conductivity testing:
Detection of conductor breaks, bad solder joints or contact problems.

3. Continuity testing:
Check function in multimeters with acoustic signal to detect a continuous current path.

4. Insulation measurement:
In special high-voltage ohmmeters (megohmmeters), the insulation resistance between conductors or to earth is measured - important in building installations or electrical machines.

5. Motor test, coil test:
Assessment of windings for continuity or short circuit.

6. Battery and cable test:
Detection of high internal resistance or line losses.

Precautions when operating ohmmeters:

When measuring with an ohmmeter, certain rules should be observed in order to obtain correct results and avoid damage to the device or object being measured:

• No voltage: Resistance measurements may only be carried out on de-energized components. Applied voltage can damage the ohmmeter or provide incorrect values.
• Avoid the risk of short circuits: If the wrong measuring range is selected, the internal current of the ohmmeter can cause damage.
• Observe temperature dependence: Resistors change their value at different temperatures - this can influence the measurement results.
• Ensure contact quality: Poor or oxidized contacts lead to falsified measurement results, especially with small resistances.

The ohmmeter is an indispensable tool in electrical engineering that is used daily in the laboratory and in practice. It provides simple, fast and reliable information about electrical connections, components and system states. Whether for troubleshooting, building electronic circuits or in safety-critical tests - the correct use of the right ohmmeter provides crucial information for the function and safety of electrical systems.

Here is an overview of the most important points to consider when purchasing ohmmeters:

When purchasing ohmmeters - whether as a stand-alone device or part of a multimeter - the focus should go far beyond the price and the measuring range specification. This is because an ohmmeter is often crucial for the diagnosis, quality testing and documentation of electrical systems. Careful selection ensures precise measurement results, high reliability and long-term cost-effectiveness.

• First of all, it must be clearly defined where and how the ohmmeter is to be used:
• For general electrical installations, simple maintenance or service work, a solid hand-held device with standard resolution is sufficient.
• For laboratory operation, research or calibration tasks, a high-precision desktop device with documented accuracy and interfaces is required.
• In industry, quality assurance or production lines, automation options, PC connection or robust designs can be decisive.
• Depending on the sector, e.g. automotive, energy technology, aviation and medical technology, different standards and accuracy requirements apply.
• The ohmmeter must reliably cover the required resistance range. Important questions are:
• Are very small resistances measured, e.g. for cables, contacts and welding points? Then a micro- or milliohmmeter with 4-wire technology and high resolution is required.
• Do high-resistance insulation resistances in the MΩ or GΩ range need to be measured? Then a special device with a high test voltage is required.
• For general applications, a wide measuring range from a few ohms to several MΩ is usually sufficient.
• The decisive factor is that the device offers sufficient resolution and accuracy in the range of interest.
• In professional applications, a specified and traceable accuracy is necessary:
• The basic accuracy should be known and documented (e.g. ±0.05 %).
• Long-term stability plays a role if the device is in permanent use.
• Calibration certificates, e.g. DAkkS, increase reliability, especially when monitoring test equipment in accordance with ISO 9001 or in certified processes.
• A key criterion for precision is the type of measurement:
• Two-wire measurement is simple, but prone to error with small resistances due to lead and contact resistances.
• Four-wire measurement (Kelvin measurement) is mandatory for very small resistances. Current and voltage circuits are routed separately in order to exclude contact resistances.
• A good ohmmeter for professional applications should at least offer the option of four-wire measurement - ideally with suitable test probes or connection sockets.
• The design and mobility requirements vary depending on the location:
• Hand-held devices are for mobile use, robust and easy to operate - ideal for field service, maintenance or installation.
• Desktop devices usually offer higher accuracy, more functions and PC connection - suitable for the laboratory and test field.
• Built-in modules or measuring cards are integrated into automated systems, for example for series test benches or end-of-line tests.
• The selection should match the infrastructure and working environment.
• A professional ohmmeter should be clearly legible, easy to use and ergonomically designed:
• Easy-to-read display, even in strong ambient light.
• Automatic range selection and reliable zero point adjustment.
• Compensation of lead resistance if required.
• Fast response time with changing measured values.
• Acoustic continuity test as an additional function for hand-held devices.
• Devices with multilingual user guidance, illuminated display or touchscreen offer additional convenience, especially for regular use.
• In professional environments, documentation of the measured values is often required:
• Devices with USB, RS232 or LAN interfaces enable connection to PCs, PLCs or data loggers.
• Software support for measured value recording, statistics or remote control is often a must for laboratory and test devices.
• SCPI or LabView compatibility is advantageous in automated test systems.
• For mobile devices, an internal memory or Bluetooth for on-site logging is helpful.
• Professional ohmmeters must work reliably even under difficult conditions:
• Robust housing, shock and impact resistant
• Protection against overvoltage, moisture and dust, e.g. IP54 or higher.
• Safety categories CAT II-IV depending on the operating environment.
• Temperature range in which the device works safely.
• Good battery life for mobile devices and short charging cycles.
• A durable device that requires little maintenance pays for itself much better than a cheap, short-lived model.
• For professional use, a calibratable device with a test report is crucial:
• Factory calibration should be standard.
• Optional: DAkkS calibration for metrologically demanding environments.
• Traceability to national standards for QA and certification.
• Compatibility with standards such as ISO, IEC, EN, CE marking.
• The availability of calibration services and spare parts is also a relevant aspect for long-term operation.
• Professional purchasing also takes soft factors into account:
• Technical support during use or fault diagnosis
• Good documentation such as manuals, tutorials and circuit diagrams.
• Availability of spare parts and repair service.
• Long-term product maintenance such as firmware updates and compatibility with new software.
• A reliable partner is often more important for devices in this class than the lowest price.

The purchase of an ohmmeter should always be based on the specific application, technical performance, long-term reliability and service support. Accurate, reliable and reproducible resistance measurements can only be guaranteed by carefully selecting a suitable device - tailored to the measurement task, application environment and system requirements. A high-quality, well-integrated ohmmeter significantly increases efficiency and safety in electrical engineering and is therefore a sensible investment in quality assurance.

Ohmmeters can be obtained from various suppliers. Comprehensive information about manufacturers and suppliers of Ohmmeters from all over the world can be found on Exportpages.