PicoLog CM3

The PicoLog CM3 Current Data Logger is designed for engineers, facility teams, laboratories and industrial users who need to monitor and record AC current consumption over short or extended periods.

The CM3 provides three independent input channels, making it suitable for both single-phase and three-phase AC current monitoring. It works with industry-standard AC current clamps that generate a voltage proportional to the measured current. This allows current to be monitored without making a direct electrical connection to the conductor being measured.

Typical applications include:

• Mains current monitoring
• Three-phase load balancing
• Machinery current monitoring
• Long-term current consumption logging
• Energy-use monitoring
• Electrical load studies
• Building services monitoring
• Industrial equipment monitoring
• Production equipment testing
• Preventive maintenance
• Electrical system troubleshooting
• ISO 14001 energy-monitoring programs

Three-Channel AC Current Monitoring

The PicoLog CM3 provides 3 measurement channels through 4 mm input sockets.

With one compatible current clamp connected to each channel, engineers can monitor:

• One three-phase electrical supply
• Three independent single-phase circuits
• Multiple machines or electrical loads
• Individual phases during load-balance testing

The three-channel architecture makes the CM3 especially useful for identifying differences between phases in three-phase electrical systems.

24-Bit Measurement Resolution

The CM3 uses a 24-bit analog-to-digital converter for detailed measurement of low-level AC signals.

Pico specifies:

• Resolution: 24 bits
• RMS noise: 60 µV
• Conversion time: 720 ms per enabled channel

The high-resolution design supports detailed current-trend logging when the CM3 is used with an appropriate current clamp.

True RMS AC Voltage Measurement

The CM3 fundamentally measures the AC voltage output produced by a connected current clamp.

Its direct electrical input specification is:

• Input range: 0 to 1 V AC true RMS
• Frequency range: 20 Hz to 1 kHz
• Input impedance: Greater than 1 MΩ
• Input coupling: AC coupled

The CM3 can therefore also be used for suitable AC RMS voltage measurements where the signal remains within its specified 1 V RMS input range.

Voltage Input Accuracy

Pico specifies the CM3 input measurement accuracy according to signal level:

• Below 200 mV RMS: ±1%
• Below 1 V RMS: ±2.5%

These figures describe the CM3 voltage-input accuracy and should not be confused with the accuracy specification of an attached current clamp.

When current clamps are used, overall measurement performance depends on both:

• CM3 input accuracy
• Current clamp accuracy and characteristics

Optional TA138 200 A AC Current Clamps

Pico offers the CM3 either as a standalone logger or as a kit with three TA138 AC current clamps.

The TA138 provides:

• Current range: 0.1 A to 200 A AC RMS
• Output sensitivity: 1 mV/A
• Accuracy: ±2% of reading, ±0.5 A
• Bandwidth: 40 Hz to 400 Hz
• Maximum conductor size: 16 mm
• Maximum output impedance: 1 kΩ
• Overvoltage protection: 600 V CAT II, 300 V CAT III

The clamp uses opening jaws that can be positioned around a conductor without making a direct electrical connection to the circuit. It also requires no battery or separate power source.

Standalone CM3 vs CM3 Kit

Pico currently provides two ordering configurations:

• PP815: PicoLog CM3 three-channel current data logger
• PP803: PicoLog CM3 kit with 3 × TA138 200 A AC current clamps

The three TA138 clamps should therefore be described as included with the CM3 kit, not as standard accessories supplied with every CM3 logger.

Non-Invasive Current Measurement

The CM3 uses external AC current clamps rather than requiring current to pass directly through the logger.

This provides several practical advantages:

• No need to break the monitored conductor
• Quick installation around suitable conductors
• No battery required by the TA138 clamps
• Suitable for temporary measurements
• Suitable for long-duration monitoring
• Easy movement between different circuits or equipment

The appropriate electrical safety procedures and clamp ratings must still be followed whenever measurements are made on energized installations.

Single-Phase Current Monitoring

For single-phase systems, one or more CM3 channels can be used to monitor individual circuits or loads.

Common examples include:

• HVAC systems
• Pumps
• Motors
• Heating equipment
• Production machines
• Building electrical circuits
• Laboratory equipment
• Electrical panels

Recorded current trends can help identify load cycles, periods of high current consumption and changes in equipment operation.

Three-Phase Load Monitoring

Using three compatible current clamps, the PicoLog CM3 can monitor all three phases of a three-phase AC installation simultaneously.

This is useful for:

• Comparing phase currents
• Detecting load imbalance
• Monitoring machine operation
• Examining load changes over time
• Identifying abnormal current patterns
• Supporting electrical maintenance decisions

Pico specifically lists three-phase load balancing as a typical CM3 application.

Long-Term Current and Energy-Use Monitoring

The CM3 is designed for long-duration recording of electrical load behavior.

With PicoLog software, engineers can record current data over hours, days or longer periods and use the captured data to investigate:

• Peak-load periods
• Machinery operating cycles
• Idle-current consumption
• Changes in production load
• Electrical demand patterns
• Energy-saving opportunities

The CM3 measures current rather than directly measuring complete electrical power parameters such as power factor and real power. Any power or energy calculations should therefore use appropriate supporting electrical data and calculation methods.

USB Connection

For portable or local measurements, the CM3 can connect directly to a computer through USB 2.0.

USB provides both:

• Data communication
• Power to the logger

Normal USB-only operation requires:

• 5 V ±10%
• Less than 100 mA

No separate external power supply is needed for standard USB operation.

Ethernet Connectivity

The CM3 also includes Ethernet connectivity for network-based monitoring.

Pico specifies:

• IEEE 802.3 10Base-T Ethernet
• Compatibility with 10/100/1000Base-T networks

This allows the logger to be positioned away from the host computer and accessed across a suitable local network.

Power over Ethernet

The Ethernet interface complies with IEEE 802.3af Power over Ethernet (PoE).

When connected to suitable PoE infrastructure, both power and network connectivity can be supplied through the Ethernet connection.

Ethernet power requirements are specified as:

• 48 V ±20%
• Less than 40 mA
• Less than 2 W

Alternatively, USB can provide power while Ethernet is used for communication.

PicoLog Cloud Software

The CM3 works with PicoLog Cloud, Pico Technology's data acquisition and logging software.

PicoLog supports:

• Real-time data collection
• Multi-channel graphing
• Channel setup
• Multiple Y axes
• Programmable alarms
• Math channels
• Notes and annotations
• Pan and zoom
• Long-duration logging
• CSV export
• PDF export
• HDF5 export for applicable cloud captures
• Multiple Pico data loggers on one computer

The software allows engineers to configure and review current measurements without requiring a custom data acquisition program.

PicoLog Cloud Remote Access

PicoLog Cloud allows compatible measurement captures to be uploaded and shared for browser-based access.

Cloud-mode specifications include:

• Up to 1 sample per second per channel
• Maximum individual cloud capture duration of 30 days
• Continuous overwrite or fixed-duration recording options
• Browser-based access to captures
• CSV, PDF and HDF5 export from compatible captures

This can be useful for remote monitoring of machinery, electrical systems and long-duration load studies.

PicoSDK for Custom Applications

Pico provides PicoSDK for engineers who want to integrate the CM3 into custom software or automated systems.

Pico publishes examples for programming environments including:

• C
• C++
• C#
• Visual Basic .NET
• Microsoft Excel
• National Instruments LabVIEW

This makes the CM3 suitable for customized monitoring, automated testing and third-party software integration.

Expandable to 60 Current Channels

Pico specifies a maximum of 20 CM3 units in a multi-logger system.

With three channels per unit:

• 3 channels × 20 units
• Up to 60 current measurement channels

PicoLog can also operate different compatible Pico data logger types together, allowing current measurements to be recorded alongside temperature, voltage and other supported signals.

Typical Applications

The PicoLog CM3 is suitable for:

• AC current data logging
• Single-phase current monitoring
• Three-phase current monitoring
• Three-phase load balancing
• Building electrical monitoring
• Machinery current measurement
• Industrial load monitoring
• Long-term current recording
• Electrical maintenance
• Energy-efficiency studies
• Equipment operating-cycle analysis
• Research and development
• Production facility monitoring
• ISO 14001 monitoring programs
• Remote electrical load monitoring