Bullhorn Tough. Bullhorn Reliable. Bullhorn Compliant.

Bullhorn RM4150S and RM4151S RMUs

Bullhorn S Series RM4150S and RM4151S RMUs are cellular-based, reliable, two-way remote monitoring units that offer unrivaled protection against surges. They are ideal for rectifiers, tanks, and well casings.

Bullhorn S Series RM4150S and RM4151S cellular, surge-hardened RMUs withstand the most extreme environments.

Why Choose Bullhorn RM4150S or RM4151S RMUs?

Bullhorn S Series RMUs monitor your critical data points, including AC and DC volts, pipe-to-soil potential, shunts, instant off, and accumulators.

Bullhorn Web

Remote Operations – Uploading measurements Bullhorn Web is automatic. Use the mobile application to change a configuration, take measurements, control interruption, and initiate instant off readings.

Reliable Interruption – Patented influence and interference technology and GPS-synchronized interruption are available when you purchase or as a field upgrade.

Rugged Durability – Bullhorn remote monitors survive the harshest conditions with built-in surge protection. For enhanced safety against surge events, you can add a high-energy surge arrester or Advanced SurgeProtect Kit.

Accuracy – RM4150S and RM4151S RMUs enable you to find and fix minor issues before they become significant. They automatically calibrate and zero each measurement, and AC and DC voltage measurements are accurate within ±1 percent throughout the range. For example, a one mV (millivolt) measurement is accurate within ±10 microvolts.

Instant Alerts – Never worry about unknown problems with your unit. Configure text or email notifications that immediately inform you about high-priority situations, such as a low battery or unusually high consumption rates.

Integrated Compliance Solution – We provide a complete end-to-end system to prove regulatory compliance. Easily import Bullhorn’s field measurements into PCS™ Compliance software and integrate them into reports.

Unlimited Warranty – American Innovations’ industry-leading warranty covers your Bullhorn RMUs against any unexpected surge damage for up to three years.

The Bullhorn RM4150S replaces the RM4150, and the RM4151S replaces the RM4151.

Learn about our full range of Bullhorn Cathodic Protection Remote Monitoring Units.



5 Analog Channels (RM4151S has 2 analog channels)

DC voltage range:

±150 V with accuracy of 1% of reading

DC voltage range:

150 V with accuracy of 1% of reading

Input impedance:

10 MΩ

Scan rate:

Once every 30 seconds

Channel-to-channel isolation:

≥ 250 V DC

Channel-to-channel isolation:

≥ 250 V DC


Survives multiple 30KV strikes. Tested using 50uS waveform to simulate lightning strike.

2 Digital Channels


Digital input, accumulator, accumulator reset, or contact closure (0 – 24 V DC)

Minimum logic:

1 = 2 V

Maximum logic:

0 = 1 V

Scan rate:

20 scans per second

Minimum pulse width:

250 ms

2 Digital Channels

Switch Out channel

Maximum current:

500 mA DC

Output voltage:

10-14 V DC

Minimum switching cycle:

1 s

On/off cycle increments:

100 ms

Interruption modes:

Daily, interference, start/stop, continuous, and Instant Of

Interference mode:

Set up to 99 rectifiers or groups for influence studies

Relay types:

NO or NC, solid state or mechanical

Instant Of

Analog channel 3:

± 10 V DC, sampled 60 times per sec

IR drop edge delay:

0 to 60 seconds in increments of 1 ms


GPS-synchronized measurement using configurable on, off, and delay settings


GSM cellular:

Worldwide compatibility on LTE cellular networks


Carrier independent. Automatically selects the best signal.

Poll, reconfigure, set alarm thresholds & update firmware over-the-air

Software Interface

Bullhorn Web

Bullhorn Tools for PC

Power Supply


100 – 240 V AC with included AC/DC converter


10 – 14 V DC (9 – 36 V DC with optional external DC/DC supply


Internal sealed rechargeable battery



Polycarbonate enclosure (5” x 2.25” x 8”)

External mount (optional):
Part #: 517200-000

Aluminum Enclosure
(7.3” x 4” x 12.4”)



-30° C to +70° C


0-95% non-condensing

Safety and Compliance


FCC Part 15

Let’s chat! Tell us about your project and we will get back with you as soon as possible.