Introduction to the Technical Specifications of a Digital Multimeter
Measurement range
In a multifunctional digital multimeter, different functions have their corresponding measurable maximum and minimum values. For example, a 41/2-digit multimeter has a testing range of 0.01mV to 1000V in the DC voltage range.
Measurement rate
The number of times a digital multimeter measures the amount of electricity being measured per second is called the measurement rate, which is measured in seconds. It mainly depends on the conversion rate of the A/D converter.
Some handheld digital multimeters use measurement cycles to indicate the speed of measurement. The time required to complete a measurement process is called the measurement cycle.
There is a contradiction between measurement rate and accuracy indicators, usually the higher the accuracy, the lower the measurement rate, and it is difficult to balance the two. To solve this contradiction, different display digits or measurement speed conversion switches can be set on the same multimeter:
Add a fast measurement mode, which is used for A/D converters with faster measurement rates; By reducing the number of display bits to significantly improve measurement speed, this method is currently widely used and can meet the needs of different users for measurement speed.
Input impedance
When measuring voltage, the instrument should have a high input impedance, so that the current drawn from the measured circuit during the measurement process is minimal and will not affect the working state of the measured circuit or signal source, which can reduce measurement errors.
For example, the DC voltage range input resistance of a 31/2-digit handheld digital multimeter is generally 10 μ Ω. The AC voltage range is affected by the input capacitance, and its input impedance is generally lower than that of the DC voltage range.
When measuring current, the instrument should have a very low input impedance, which can minimize the impact of the instrument on the tested circuit when connected. However, when using the current mode of the multimeter, due to the small input impedance, it is more likely to burn out the instrument. Please be careful when using it.
