i-Spy: Advanced 3-Phase AC Current Monitor with Modbus/RTU


  • True RMS, 0.1% accuracy, wide dynamic range.
  • Supports a wide variety of solid core and split core CTs.
  • Modbus/RS-485 communication (up to 63 devices per chain).
  • Customizable scaling, filtering, Modbus map, and serial settings.
  • Compact Size, Easy Wiring, DIN Rail Mounting.
  • Ideal for Control and Energy Management Applications.


The i-Spy transducer offers inexpensive yet accurate true RMS monitoring of AC current in three independent circuits or one three-phase circuit.

This unique product is ideal as a precision AC load monitor for Control and Energy Management applications.

The i-Spy combined with inexpensive current transformers provides a convenient tool for accurate load monitoring in any electrical equipment.

Product Description

The i-Spy is a microprocessor-based precision current monitor that performs true RMS current measurements in one three-phase circuit or in three independent AC loads. This device is backwards-compatible with existing ETA3.RTU transducers.

The unit supports standard 5A current transformers as well as a variety of current sensors including split and solid core CTs and precision sensors that may be applied to the secondary wires of existing 5A CTs.

The i-Spy measures true RMS current in each of the three inputs and provides output data (via Modbus RTU) that is proportional to the RMS current in each input, the averaged current {Iavg= (I1+I2+I3)/3}, and the total current (Itotal= I1+I2+I3). Configurable scaling factors can be applied to the output values for ease of use and compatibility.

A proprietary noise filtering technique is employed to expand the dynamic range of the device and to improve the accuracy and stability of readings at low currents.

The i-Spy supports the Modbus RTU protocol with configurable baud rate (up to 57600), parity, and stop bit settings. Up to 63 devices can be present on the RS-485 chain. The device's registers are available in 16-bit integer, 32-bit integer, and 32-bit floating-point formats with configurable scaling. The Modbus register map is customizable and may be user-adjusted for efficiency or compatibility with other devices.

For easy visual monitoring and commissioning, the device has configurable bi-color LEDs on each current channel, as well as communication and status LEDs. The current LEDs can be configured to show green, red, or off at different current thresholds.

The i-Spy is powered by 12-30 VAC/VDC. The unit is housed in a universal DIN mount enclosure and features screw-type terminal blocks for easy field wiring.


Power12-30 VDC/VAC
InputStandard CTs, 5A or 1A
Elkor Current Transformers (solid/split core -- MCT/MSCT):
333mV output CTs
Output RS-485 digital communication port. Up to 63 devices per line.
Modbus RTU (functions 3, 4, 6, 8, 11, 16, 17, 22, 23 and 43)
Baud rates: 9600 (default), 19200, 38400, 57600
Parity: None (default), odd, even
Stop bits: 1 (default), 2
Data Width: 8
AccuracyTRMS, 0.1% of reading, output resolution of up to 20 bits
Temperature Range-40°C to 70°C, RH 90% non-condensing
EnclosureDIN Rail - universal DIN attachment mounted on the back of enclosure; dim. h=3.75" w=2" d=2.25" (95x50x60mm).

Ordering Information

i-Spy-[CT Type]

Where [CT Type] Specifies CT Input Type: 

5A Inputs for 5A CTs

Inputs for mA output CTs.  200mA output Max (see below)
MCT Series
MS Series
MSCT Series
MRA Series
333mV Inputs for 333mV CTs

*** Contact Elkor for other input options



   Specifies transducer for use with mA output CTs such as MSCT1.

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