Merlin6 AC Monitor by Abriox

Monitors Daily AC Standing Voltage and Current Flow to Coupon. Isolated DC and AC Monitoring.


The MERLIN CP Hemi Monitor is a compact unit designed to fit invisibly within a CP riser post. It collects Cathodic Protection (CP) data and communicates using the cellular GSM network. MERLIN CP Hemi records pipe-to-soil potentials and current levels, checks that they are within specification and reports immediately if an alarm threshold is exceeded. Alternatively it may simply be that certain measurement points on the pipeline create risks to CP technicians, such as at busy road or rail crossings, or are difficult to access, such as on private land. At these points remote monitoring is very cost-efficient and can improve safety.

Two key features of the Abriox system are:

  • Cellular telephone control, which is all that is required to set up and configure MERLIN CP Hemi monitors. This makes installation really quick and easy (typically just 20 minutes at a test post) without the need for any special equipment.
  • AC monitoring on all channels to identify a possible corrosion threat - and protect the workforce from dangerous voltages or currents.

All data is automatically transmitted in a management report to the system HQ where it is available on-line using Abriox’s MERLIN iCPSM software. ICPSM provides access from any internet-enabled PC to a passwordprotected CP database, unique to each customer.

Users can configure and control MERLIN monitors, view CP data in graphical and numerical formats or export data for further analysis and archiving.



  • DC and AC monitoring for full corrosion prevention
  • Fully automatic system - data sent in automatically, wirelessly
  • Email or text message alarm when pipeline CP levels are inadequate
  • Reduced cost of measurement, especially at remote locations
  • Engineering time freed up for data interpretation and follow-up
  • Reduced risk to workforce at dangerous or remote sites
  • Compact size for easy installation inside the riser post
  • Zero carbon footprint for CP monitoring - no vehicle surveys required



  • Designed for easy installation in the riser post—typically 20 minutes on site. Color-coded connections to pipe/electrode/ coupon.
  • Daily CP level check (hourly option for problem solving).
  • Alarms reported immediately (user preset thresholds for all channels).
  • Weekly report gives min, max and average of all channels for the week.
  • 5-year life, batteries replaceable.
  • Sealed, weatherproof unit with robust lightning protection and wide operational temperature for all extremes.
  • Test and set-up from cellular telephone using text messaging.
  • Web-based user interface with graphical/tabular displays and data export.


GSM (SMS) Communications

Batteyry Backup

GSM (SMS) Communications

Test and set up from cell phone using
text messaging

Battery Backup5 year life, replaceable battery module.
User Alerts

Synchronized Interruption

User AlertsAlarms reported immediately (user preset
thresholds for all channels).
Synchronized InterruptionPair of relay contacts, normally closed. Contacts open whilst channel 2 is read.

Electrical Supply Monitoring

Custom Reports
AC Power MonitoringAlarm sent when protection levels inadequate – so that protection can quickly be restored to the pipeline.
Custom ReportsData automatically archived and presented in custom report formats or exported to other standard applications.

Daily or Weekly Reports

Daily or Weekly ReportsWeekly report gives min, max and average
of all channels for the week
Weight 520g (1.1lb)

Operational Remperatures

Lightning Protection
Operational Temperatures-40°C to +85°C (-40°F to +185°F). 100% condensing humidity.

IP Rating

Surge protection on all external inputs and outputs. 2,500A at 3,000V (8/20us). Additional protection using recommended surge arrestors.

IP Rating

IP Rating
The MERLIN CP Hemi Monitor is IP67 rated. Offering protection against falling dirt, rain, sleet, snow, windblown dust, splashing, hose-directed water and temporary immersion.

Technical Specification

The MERLIN CP Hemi Monitor is a compact, robust, long-life unit that monitors cathodic protection levels at a cylindrical test post. Its key features are:

  • Narrow diameter fits invisibly within cylindrical riser
  • DC and AC monitoring for full corrosion prevention
  • Alarm sent when protection levels inadequate
  • Reduced cost of measurement, especially at remote locations
  • Engineering time freed up for data interpretation and follow-up
  • Health & Safety – reduced risk at roads/properties, eliminates lone-worker issues
  • •Zero carbon footprint for CP monitoring – no vehicle surveys, fully automatic system


Physical Dimensions

Physical Dimensions
(H x W x D)

10.8” x 3.15” fits invisibly within standard 3.5” riser post



IP Rating


Operating Temperature

-40°F to +185°F 100% condensing humidity

Lightning Protection

Surge protection on all external inputs and outputs

2,500A at 3,000V (8/20us)

Backup Battery

5-year life, replaceable battery module


Cellular (GSM/SMS)

Software Management

iCPSM (web based) or CPSM (PC based)

  • Two pipe-to-soil inputs
    • 10 MOhm input impedance
    • ± 4V DC with AC rejection
    • 1mV resolution
    • 0-70V AC RMS, 10mV resolution
  • Current shunt input
    • 0-100mV
    • 0.01mV resolution
  • AC and DC current measured
  • All monitoring channels are fully independent
  • Pair of relay contacts, normally closed
  • Contacts open while pipe to soil input 2 is read
  • Contacts rated at 1A at 30V DC

MERLIN CP Hemi can be deployed at any test point on the pipeline network, such as: mid-points between rectifiers or pipeline terminations (low CP levels), pipeline crossings or corridors (sources of interference from foreign systems), pipelines close to, or parallel with, power lines (sources of AC interference) and rectifier drain points (to check rectifier output levels).





Pipe-to-Soil 1

Pipe-to-Soil 2
Instant OFF 

Coupon Current 
Bond Current 



1 Channel

2 Channel

3 Channel


MERLIN CP monitors use GSM SMS messaging to report data from the field to a central HQ. This method has several advantages:

GSM SMS Communications

  • Massive investment in infrastructure by GSM network providers
  • Excellent coverage in virtually all urban and semi-urban locations
  • Expanding coverage worldwide into remote/rural areas
  • Proven reliability
  • Low cost.


SMS communication enables MERLIN monitors to be set up in the field using a cellphone.

MERLIN monitors incorporate an internal GSM antenna which, in most locations, will be quite adequate. In weak signal areas, units can be equipped with an external antenna.

The MERLIN system is independent of network provider and Abriox will work with users to secure the most advantageous communication package in their country. We can usually supply our monitors with a GSM airtime package – but we can also factory fit free-issued SIMs or supply monitors for users to fit their own SIMs.