A bench type digital multimeter (DMM) is a precision electronic measuring instrument designed for use on a workbench or laboratory setting. Unlike handheld multimeters, bench DMMs are larger, more robust, and typically offer higher accuracy, resolution, and a wider range of measurement capabilities. They are used for testing and diagnosing electrical and electronic circuits, components, and systems. Key features of bench type digital multimeters include: 1. **High Accuracy and Resolution**: Bench DMMs provide precise measurements with high resolution, often up to 8.5 digits, making them suitable for applications requiring exact data. 2. **Multiple Measurement Functions**: They can measure various electrical parameters such as voltage (AC/DC), current (AC/DC), resistance, capacitance, frequency, and sometimes temperature. Advanced models may also measure inductance, conductance, and other parameters. 3. **Data Logging and Connectivity**: Many bench DMMs offer data logging capabilities, allowing users to record measurements over time. They often include interfaces like USB, GPIB, LAN, or RS-232 for connectivity with computers and other devices, facilitating remote control and data analysis. 4. **User Interface**: These multimeters typically feature a large, easy-to-read display, often with graphical capabilities, and intuitive controls for ease of use. 5. **Durability and Stability**: Designed for long-term use, bench DMMs are built to withstand the rigors of a laboratory environment, providing stable and reliable performance over time. 6. **Advanced Features**: Some models offer additional features such as mathematical functions, limit testing, and automated test sequences, enhancing their utility in complex testing scenarios. Bench type digital multimeters are essential tools in research and development, manufacturing, and quality control environments, where precision and reliability are critical.

A bench multimeter and a handheld multimeter differ primarily in terms of design, functionality, accuracy, and application. 1. **Design and Portability**: Bench multimeters are larger, stationary devices designed for use on a workbench or in a laboratory setting. They are typically AC-powered and have a more robust build. Handheld multimeters are compact, battery-powered, and portable, making them suitable for fieldwork and on-the-go measurements. 2. **Functionality and Features**: Bench multimeters offer advanced features and higher precision. They often include multiple measurement functions such as voltage, current, resistance, capacitance, frequency, and temperature, with more digits of resolution. They may also have additional capabilities like data logging, connectivity options (USB, GPIB, LAN), and programmable interfaces. Handheld multimeters provide basic measurement functions and are designed for general-purpose use, with fewer features and lower resolution. 3. **Accuracy and Precision**: Bench multimeters provide higher accuracy and precision due to their advanced circuitry and calibration standards. They are suitable for applications requiring precise measurements, such as research and development, calibration labs, and quality control. Handheld multimeters, while accurate for everyday use, have lower precision and are more suited for troubleshooting and maintenance tasks. 4. **Application and Use Case**: Bench multimeters are ideal for environments where high accuracy and advanced measurement capabilities are required, such as laboratories and manufacturing facilities. Handheld multimeters are used by electricians, technicians, and engineers for field service, repair, and maintenance tasks due to their portability and ease of use. In summary, the choice between a bench and a handheld multimeter depends on the specific requirements of accuracy, functionality, and portability for the intended application.

When selecting a bench multimeter, consider the following key features: 1. **Accuracy and Resolution**: Look for high accuracy and resolution to ensure precise measurements. A multimeter with a higher number of digits (e.g., 6.5 digits) offers better resolution. 2. **Measurement Functions**: Ensure it can measure voltage, current, resistance, capacitance, frequency, and temperature. Additional functions like continuity, diode testing, and data logging can be beneficial. 3. **Input Ranges**: Check the range of input values it can measure. A wide range allows for versatility in different applications. 4. **Display**: A clear, large, and backlit display is crucial for readability. Some models offer dual displays for simultaneous measurement readings. 5. **Connectivity**: Look for USB, RS-232, GPIB, or LAN connectivity for data transfer and remote operation. This is essential for integration into automated test systems. 6. **Build Quality and Durability**: A robust build ensures longevity, especially in industrial environments. Consider models with protective features like overvoltage protection. 7. **Ease of Use**: Intuitive interface and easy-to-navigate menus enhance user experience. Soft keys and rotary knobs can simplify operation. 8. **Calibration and Certification**: Ensure the multimeter is calibrated and comes with a certificate of calibration for traceability and compliance with standards. 9. **Sampling Rate**: A higher sampling rate allows for capturing fast-changing signals accurately. 10. **Brand and Support**: Opt for reputable brands known for reliability and customer support. Availability of service centers and warranty terms are also important. 11. **Price and Budget**: Balance features with budget constraints. Higher-end models offer more features but at a higher cost. 12. **Software Compatibility**: Check for compatibility with software for data analysis and reporting. These features collectively determine the multimeter's suitability for specific applications, ensuring accurate and efficient measurement tasks.

To calibrate a bench multimeter, follow these steps: 1. **Preparation**: Ensure the multimeter is in a stable environment, free from temperature fluctuations and electromagnetic interference. Allow it to warm up for at least 30 minutes. 2. **Reference Standards**: Use precision reference standards that are at least four times more accurate than the multimeter. These include voltage, current, and resistance standards. 3. **Initial Checks**: Inspect the multimeter for any physical damage or signs of wear. Verify that the display and buttons function correctly. 4. **Voltage Calibration**: - Connect the multimeter to a DC voltage standard. - Set the multimeter to the appropriate voltage range. - Compare the multimeter reading with the standard. Adjust the multimeter if necessary using its internal calibration controls or software. 5. **Current Calibration**: - Use a precision current source. - Set the multimeter to the correct current range. - Measure the current and compare it with the source. Adjust as needed. 6. **Resistance Calibration**: - Connect the multimeter to a precision resistor. - Set the multimeter to the resistance measurement mode. - Compare the reading with the resistor's value. Make adjustments if required. 7. **AC Measurements**: - For AC voltage and current, use an AC calibrator. - Follow similar steps as for DC measurements, ensuring the multimeter accurately reads AC values. 8. **Documentation**: Record all calibration results, adjustments made, and the equipment used. This documentation is crucial for traceability and future reference. 9. **Final Verification**: Recheck all measurements to ensure consistency and accuracy after adjustments. 10. **Seal and Label**: Once calibrated, seal the multimeter to prevent tampering and label it with the calibration date and due date for the next calibration. Regular calibration ensures the multimeter's accuracy and reliability in measurements.

The accuracy level of a bench multimeter depends on the specific model and manufacturer, but generally, bench multimeters are known for their high precision and accuracy compared to handheld multimeters. Accuracy is typically expressed as a percentage of the reading plus a number of least significant digits (LSD). For example, a bench multimeter might have an accuracy specification of ±(0.01% + 2 LSD). High-end bench multimeters can offer accuracy levels as precise as ±0.0035% or better for DC voltage measurements. These devices are often used in laboratory settings, calibration facilities, and other environments where precise measurements are critical. Mid-range bench multimeters might have accuracy levels around ±0.05% to ±0.1%, which is still suitable for many professional applications. The accuracy can vary across different measurement functions such as voltage, current, resistance, capacitance, and frequency. Typically, DC measurements are more accurate than AC measurements due to the complexities involved in measuring alternating currents and voltages. Temperature, humidity, and other environmental factors can also affect the accuracy of a bench multimeter. Manufacturers often provide specifications for operating conditions to ensure optimal performance. Regular calibration is necessary to maintain the specified accuracy over time. In summary, the accuracy level of a bench multimeter is a critical specification that varies by model and manufacturer, with high-end models offering superior precision suitable for demanding applications.

To measure current, voltage, frequency, and resistance with a bench multimeter, follow these steps: 1. **Current Measurement**: - Turn off power to the circuit. - Connect the multimeter in series with the circuit. - Select the appropriate current range on the multimeter. - Turn on the circuit power and read the current value displayed. 2. **Voltage Measurement**: - Ensure the circuit is powered. - Connect the multimeter probes across the component or section of the circuit where voltage is to be measured. - Select the appropriate voltage range (AC or DC) on the multimeter. - Read the voltage value displayed. 3. **Frequency Measurement**: - Connect the multimeter probes to the circuit where frequency measurement is needed. - Select the frequency measurement mode on the multimeter. - Read the frequency value displayed. 4. **Resistance Measurement**: - Turn off power to the circuit and discharge all capacitors. - Remove the component from the circuit if possible. - Connect the multimeter probes across the component. - Select the resistance measurement mode on the multimeter. - Read the resistance value displayed. Always ensure the multimeter is set to the correct measurement type and range to avoid damage to the device or inaccurate readings.

Some of the best brands for bench-type digital multimeters include: 1. **Fluke**: Known for reliability and precision, Fluke offers a range of bench multimeters that are highly regarded in both industrial and laboratory settings. Models like the Fluke 8845A and 8846A are popular for their accuracy and durability. 2. **Keysight Technologies (formerly Agilent)**: Keysight is renowned for its high-performance test equipment. Their bench multimeters, such as the Keysight 34461A and 34470A, are favored for their advanced features and precision. 3. **Tektronix**: Tektronix provides robust and reliable bench multimeters suitable for various applications. The Tektronix DMM4050 and DMM4040 are well-regarded for their measurement capabilities and user-friendly interfaces. 4. **Keithley Instruments**: A subsidiary of Tektronix, Keithley is known for its precision measurement instruments. The Keithley 2000 and 2010 series are popular choices for their high accuracy and extensive functionality. 5. **Rohde & Schwarz**: This brand is known for its high-quality test and measurement equipment. The R&S HMC8012 is a versatile bench multimeter that offers excellent performance and reliability. 6. **GW Instek**: Known for providing cost-effective solutions, GW Instek offers reliable bench multimeters like the GDM-8342, which are suitable for both educational and professional environments. 7. **B&K Precision**: B&K Precision offers a range of affordable yet reliable bench multimeters. Models like the B&K Precision 5491B are appreciated for their ease of use and solid performance. These brands are recognized for their commitment to quality, accuracy, and innovation in the field of electronic measurement, making them top choices for professionals and enthusiasts alike.