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Several months ago, Virtjoule converted the vibration sensors on four compressors at Niwot Market over to the Virtjoule Juice Cellular CT.  Because there were two large Copeland compressors on each rack, there was a lot of vibration from one compressor being picked up on sensors for other compressors, what we call “cross-talk”.

Our goal for Virtjoule Juice Cellular CT was to isolate the runtime of each compressor by itself, making it easier to visually and programmatically analyze what was going on.

Remote mounting board for Cellular CT's

Remote mounting board for Cellular CT's

Key Points

CT’s are very good at isolating runtime behavior of components in more complex or integrated system of machines.

CT’s can be run a very long distance from the source to the Virtjoule sensor, 100′ or more.

Virtjoule Juice Cellular CT’s are like having someone standing with a clamp meter on a machine 24/7.

Need To Know It’s Running

The primary thing Bert Steele, owner of Niwot Market, needs to know is whether the compressors are running or not.  Oil temperature problems, refrigerant changeover, refrigerant leaks, and plain old worn out compressors have caused numerous problems over the time.  All of those problems have caused shutdowns on these critical compressors.  Sometimes it was a single compressor.  Sometimes the whole rack.  Virtjoule’s monitoring service and its ability to tell him his compressors are running has been critical to running a tight margin grocery business.

The compressor racks at Niwot Market have been one of the toughest environments for the Virtjoule vibration input sensors.  There are four compressors total, two each on a rack.  Because these are heavy compressors, when one operates it will vibrate the entire rack.  We were still able to distinguish one compressor from another via vibration, but analysis was more difficult and not as clear to the customer as we would have liked.

Niwot Market Low Temperature Rack

Niwot Market Low Temperature Rack

CT Installation

It’s easy to install CT’s.  Simply pull the top off the CT, wrap the body of the CT around the alternating current wire you’re interested in, and put the top back on.

Magnelab 70 amp CT on one of three phases

Magnelab 70 amp CT on one of three phases

The CT Run

In this installation, the compressors are in a basement room, underneath a corrugated metal and concrete floor, and situated near the center of the building.  Needless to say, cellular coverage from this location was not good.  We were able to find a location in a stairwell that gave us good cellular reception, but was still out of the way, yet accessible.


Virtjoule Juice Cellular CT’s can easily isolate and monitor electrical components such as large electric motors, compressors, fans and blowers, chlorine generators, sump pumps, air conditioners, walk-in and reach-in refrigerations, and many more types of critical electric machinery.

With amperage information, you can not only make power estimates, you can use Virtjoule’s 10 second data to determine if the machine is running, how often it’s cycling on and off, how long those cycle times are, and produce critical alerts via text, email, or callout.

[Randy Cox - CEO and co-founder of Virtjoule - He is the software designer and analytics engineer for Virtjoule Sense sensors. He studied Chemical Engineering and Petroleum Refining at the Colorado School of Mines. You may contact Randy at: randy at virtjoule dot com] – See more at:


Virtjoule has been in production and in the field with a new Cellular CT device called Virtjoule Juice.  It’s a new continuous monitoring system for amperage readings used on any type of equipment electric motors or other types alternating current draw.

The new Virtjoule Cellular CT has been calibrated with the Magnelab SCT-0750 line of industrial current transducers (CT) making it both accurate and flexible for reading amperages from 0 to 3,000 amps.

With the Virtjoule Cellular CT sensor and monitoring service, you can find problems such as short or long cycles, over or under amperage conditions, and after hours operations, all of which may indicate operational problems which should be corrected before becoming expensive repairs, large utility bills, or interrupting critical business processes.

Monitor Amperage and Power

Current transducers are a special type of sensor that can not only tell if current is flowing through an alternating current wire, it can also tell you how much amperage is flowing through the wire which is useful for both fault detection and energy studies.

First dedicated cellular CT on the market

This is the first low-cost dedicated cellular CT available on the market.  Other CT products are available on the market, but they are either unconnected loggers that have to be retrieved and uploaded or are connected to gateway devices that cost well over $1,000 and don’t stand alone.

CT’s are sized and based on the electrical current used on one leg of an alternating current wire.  Sizes can go from 5 to 200 amps in the SCT-0750 line and up to 3,000 amps on other parts of the Magnelab CT lineup.

Virtjoule cellular CT with Magnelab 20 amp CT

Virtjoule cellular CT with Magnelab 20 amp CT

A Must-Have Tool for Energy Auditors, Retro-Commissioning, and Service Providers

A cellular CT will become a must-have tool.  Energy auditors, retro-commissioning specialists, and service providers are all aware of the basic usefulness of a regular handheld CT.  24/7/365 monitoring via CT gives you the ability to isolate a single component of a machine or the flexibility to find the variable energy use of an entire machine.

Virtjoule has been known for excellent fault detection capabilities and using a CT is now one more way to tap into fault detection capability in addition to understanding the energy usage of a machine.

True RMS

The Virtjoule Juice Cellular CT is a True RMS sensor.  In addition to normal sinusoidal power feeds, it can be used to accurately measure amperage on variable speed devices and other pulse width modulated machines where computing the True RMS is key to knowing the correct amperage.  Knowing correct amperage is critical to knowing how much power a machine is using and, for that matter, what parts of the machine are running.

How can you use a Cellular CT?

Cycling and hours of operation

Use the Cellular CT to pick up runtime information which includes amperage levels, cycling behavior, and hours of operation.

Failing compressors

It’s a well known fact that most aging compressors will begin to draw more amps, not only on startup, but at runtime as well.  We have seen a recent example where amperage monitoring showed that a compressor was at the end of its life and we caught the actual failure when it happened.  Monitoring amperage can give you insight into machine life expectancy issues.

Locating energy wasters

Use the Cellular CT to do sub-metering on selected units.  With power output estimates from known amperage, it’s now possible to find those energy hogging machines.

Use the Cellular CT to demonstrate how much after hours operations cost.  By monitoring the machine 24/7, you know when it is running after hours.  Because you now have amp information, along with voltage and power factor it’s now possible to closely estimate how much after hours operations are costing.  Virtjoule can help you do that.

Monitor complex behavior of individual components

Cellular CTs can be used to monitor specific electrical components of a much more complex machine.  For instance, you can know conclusively at any time how many stages of compressors are being used in a large package unit.  Also, estimating energy usage on larger and more complex machines can be very inexact because you can only estimate just exactly how the machine is used.  Rules-of-thumb break down, particularly on larger machines.  Now you can find out exactly how the machine is being used and how it’s performing.

Because amperage can be turned into power information and because we’re taking 10 second averages of amperage, you can get very accurate estimates of power usage on any electrical machine, motor, or other electrical component of a machine.

Multi-tenant situation, expense sharing

Do you have a multi-tenant situation, but sub-metering is not possible?  Use Cellular CTs to understand power use across shared machines or electrical input and allocate costs appropriately and fairly.

Comparing a standard “clamp meter” with Virtjoule Juice Cellular CT

Clamp Meter vs Cellular CT

Clamp vs Cellular CT

Available now

Virtjoule Juice Cellular CT is available now.  Call us today to discuss how Virtjoule Juice Cellular CT can help you or your clients and get your order in for this first of a kind monitoring device.

[Randy Cox - CEO and co-founder of Virtjoule - He is the software designer and analytics engineer for Virtjoule Sense sensors. He studied Chemical Engineering and Petroleum Refining at the Colorado School of Mines. You may contact Randy at: randy at virtjoule dot com] – See more at: