This is a followup to my road test review.  While doing some of the tests that I proposed in my road test application, I thought of a few others.  This was the one that jumped to the top of the list.

The application is monitoring a building's current draw, both quantity and characteristics - such as large motor inrush demands caused by overhead cranes, etc.  Sometimes this type of survey is used to determine the size of a backup generator.  Sometimes it is used to determine if other loads can be added to an existing backup generator.  Electricians use it to chase electrical problems.  Is the issue intermittent or does it have a pattern?  All cool stuff.


When we do this with power meters, we make all the connections, close up the electrical panels as best we can and place the power meter where we can and leave.  We come back at a later date, save the data, recover the system and leave.

Wouldn't it be helpful to see what's going on while it's going on?  To get an indication of where the data might be leading us?

It's also nice to know that the system is working correctly once everything is buttoned up.  Sometimes an accidental button push costs you another week or month of logging.


The PicoLog CM3 AC Current Data Logger has network capabilities, either as a monitoring node on a network when using the Windows PicoLog 6 software or through a computer on the network (Windows, Mac, Linux or RPi).

But what happens when you're a service technician and the customer doesn't want you on their network?          I know.  I am crazy to suggest such a thing, but it does happen.

I guess we need to create our own network.


Of course, the Raspberry Pi 4 is perfectly suited for this application.  The only hotspot application that I know of is autohotspotN.  Most importantly, it works.

For those that want to install it the long way,…

For those that would like a simple method, Jason, KM4ACK, has a script.


To insure that my RPi4 used its own hotspot all the time, I removed all of the known networks from wpa_supplicant.conf.

Because not everything goes as planned, the IP of the hotspot is  When wirelessly connected to the hotspot with a laptop, I used PuTTY to log into the RPi4 and start the VNC server.  From there, I was able to use RealVNC to launch and run the PicoLog 6 software.


I think I'll install this on the electrical service at my training center.  Let's get started...

Starting point.  Those are compact fluorescent lights on the left panel.  I really need to do better housekeeping.  Remove panel face.  Add current clamps.

Service Entrance Panel Current Clamps


The RPi4 is going to need power.  Fortunately, there is a spare breaker in the panel.  Add convenient plug.  Connect clamps and USB.  Place CM3 neatly in cabinet.

RPi4 Power PicoLog CM3 in Cabinet


I did choose to pop out one of the knockouts instead of trying to sneak the cables from beneath the cover.  Add cover.

RPi4 on Cabinet Ready for CoverCabinet Closed


Turn on circuit breaker and power up the RPi4.  Go fetch laptop.  Join RPiHotspot - which I renamed PicoLogHotspot.  I'm still not having any luck auto-starting the VNC server.  It did for a while and now it doesn't.  So, PuTTY to the rescue.  SSH in.  Launch vncserver.  Log in with RealVNC.  Launch PicoLog 6.

PicoLogHotspot Add VNC Node PicoLog 6


Here's what the data log looks like after about an hour and over night.  I did have to go back and change the scaling on the current clamps when I first started, but I only lost 2 or 3 minutes of recording.

Data Log Overnight Data Log

I snapped this while sitting at my desk 30-ish meters from the panel.

The PicoLog CM3 AC Current Data Logger is quite versatile.  The average person wouldn't even notice the Raspberry Pi on the cabinet.  THIS is exciting stuff - at least to a generator nerd.