Merlin6 CP Monitor by Abriox

A Compact Unit Housed Within or Adjacent to a Test Station or Bond Box


The MERLIN CP Monitor is a compact unit housed within, or adjacent to, a Test Station or Bond Box. It collects Cathodic Protection (CP) data and communicates (via either an internal or external antenna) using the cellular network.

MERLIN CP monitors collect CP data automatically, check that it is within specification and report immediately if an alarm threshold is exceeded. They can be deployed anywhere on the pipeline network where it is important to record pipe-to-soil potentials or measurements of bonding or interfering currents.

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
  • 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 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.
  • Zero carbon footprint for CP monitoring.
    • no vehicle surveys required, fully automatic system.
  • Small size for deployment at test stations, bonds etc.



  • Compact size - quick and easy to install, typically 20 minutes on site
  • Daily CP level check (hourly optional 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.

IP Rating


IP Rating

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

Weight 450g (1lb)

Daily or Weekly Reports

Lightning Protection
Daily or Weekly ReportsWeekly report gives min, max and average
of all channels for the week

IP Rating

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

Operational Remperatures


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


Lightning Protection

Testing performed on the new MERLIN design showed that:

  • A “naked” MERLIN easily survives 2500A at 3kV (8/20us pulse) via AC or from the pipeline – a substantial surge.
  • With Abriox’s recommended external surge arrestors in place, the MERLIN withstands10kA, 10kV without damage - a massive surge.
  •  Even bigger surges (29kA) can be survived by MERLIN - but the external surge arrestors may be blown to pieces!

Technical Specification

The MERLIN Transformer Rectifier Monitor is a compact unit designed to monitor and report the operation of a rectifier. Its key features are:

  • Alarms and periodic reports sent to a central HQ using GSM SMS communication
  • Fully independent monitoring channels (allow high-side or low-side shunt and accurate ON potential measurement)
  • Installation by cellphone
  • Remote control of rectifier output from cellphone and/or software.

Physical Dimensions

Physical Dimensions
(H x W x D)

5” x 3.5” x 2”



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


Typical installation locations for the MERLIN CP Monitor include: mid-points between rectifiers or pipeline terminations (low CP levels), pipeline crossings or corridors (sources of interference from foreign systems), critical bonds between pipelines (the direction of the bond current can even be monitored), isolation joints (to check potentials either side of the IJ), 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

Pipe-to-soil potential measurements (Premium and higher) at the rectifier require a reference cell and relay. Remote synchronization (Super and Excel) require a MERLIN solid state Interrupter.


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.