Digital ammeters are instruments that measure current flow in amperes and display current levels on a digital display. These devices provide information about current draw and current continuity in order to help users troubleshoot erratic loads and trends. They have both positive and negative leads and feature extremely low internal resistance.

Digital ammeters are connected in series with a circuit (and never parallel) so that current flow passes through the meter. High current flow may indicate a short circuit, unintentional ground, or defective component. Low current flow may indicate high resistance or poor current flow within the circuit.

Measurement Type

Digital ammeters can measure levels of alternating current (AC) and direct current (DC). Some devices that measure AC current also measure root mean square (RMS) power, which is the square root of the time average of the square of the instantaneous power. Many digital ammeters include a current sensor built into the meter or that clamps around the wire. Different types of digital ammeters can measure different ranges of AC current, DC current, and AC current frequency.

Form Factor

Some devices are handheld and portable, while others are designed for benchtop or shop floor use. Battery-powered digital ammeters can be operated without plug-in power and are often suitable for outdoor use.

Features

Many digital ammeters provide special measurement types or advanced options or features.

• Adjustable sampling rate - The sampling rate is manually adjustable.
• Alarm LED - Alarm light-emitting diodes (LEDs) light when the RMS value or peak value is greater than the range. Typically, alarm LEDs light only when the range has been greatly exceeded.
• Application software - The device has embedded application software.
• Auto-Ranging - Auto-ranging devices are self-adjusting to offer the best measurement scenario.
• Battery powered - Devices are battery-powered.
• Data acquisition - Devices with data acquisition capabilities have a computer interface and software for uploading data.
• Data storage / logging - Data storage or data logging devices have internal memory for storing data.
• dB readings - Devices measure values in decibels (dB).
• External shunts - External shunts can be used to extend the current input range. For example, an input that exceeds 5 A can be measured by providing a shunt.
• Filters - Devices have embedded filters.
• Integrating functions - Integrating functions allow the active power and current to be integrated (Wh and Ah).
• Mirrored scale - Mirrored scales make it easier to read the instrument to a given accuracy by enabling the operator to avoid parallax errors.
• Overload protection - Devices with overload protection have fuses or other devices to protect the meter.
• Programmable - Programmable devices can be programmed with trigger values to perform measurements.
• Range switch - Range switches can be used to select an appropriate range of units to be measured.
• Removable data storage - Devices with removable data storage have removable memory, drives, etc.
• Scaling function - Devices with a scaling function allow the pre-setting of the potential transformer and current transformer ratio, and the power scaling factor.
• Temperature compensated - Temperature-compensated devices are designed to counteract known errors caused by temperature changes.
• Triggering - Devices with triggering have an interface for external triggering.

In terms of advanced options, digital ammeters can:

• Adjust sampling rates automatically
• Display status information as a bar graph
• Measure decibel readings

Standards

Digital ammeters must adhere to certain standards and specifications to ensure proper design and functionality. 

BS 89 P2: Classification, construction, marking, electrical and mechanical requirements, and tests for analogue ammeters and voltmeters. To be read in conjunction with BS 89:Part 1

IEC 60051-2: Direct acting indicating analogue electrical measuring instruments and their accessories. Special requirements for ammeters and voltmeters.

KS R 5025: Ammeters for Automobiles.

Image Credit:

Dwyer | Hoyt Electrical Instrument