Well, it is not so much that they are uncommon. But they are expensive. It’s not really a CT meter (current transformer) since DC doesn’t play with a transformer, it uses a hall effect sensor, which is a sensor that reacts to a magnetic field (even one that is stationary).
The cheasest DC-capable clamp meter I could find is the Majortech MTD75T. It’s about R1500. It is very plasticky, and definitely not rated for hard industrial type work, but for a DIYer who’s just using it every 7th weekend or so, it will do just fine.
1 Like
Indeed! I suppose the term is a ‘clamp meter’
But these meters are such a pleasure since reading current values is so easy.
1 Like
This how I do it.
My MPPTs are rated for 150V, which means two panels in series max’s out my voltage. I just get too close to 150V with my possible low temperatures.
I use 6mm wire which allows me to make all my connections with 30A MC4 connectors.
Then I parallel up on the roof sometimes 2S3P or 2S4P depending on panel orientation to give me a Imp of just under 30A.
These equal voltage strings are then brought down to a ground level combiner box.
Each 30A string ( + & - wire together) passes through a torroid ferrite core (Every little bit of lightning protection helps) and then a combination of strings are combined onto a DC MCB.
From the DC MCBs it’s off to the respective MPPTs.
I combine each MPPT’s input strings on a single DC MCB, so as to optimise my MPPT’s.
All the strings are of the same voltage, so I mix and match E, W & N strings, so as to match the noon peak to the respective MPPT’s capability.
This means I don’t have the facility to easily switch out a single 30A string at a time for testing purposes.
Sure it’s easy enough to measure the individual current contribution with a clamp meter, and I do do that after any modifications.
But I wanted something simpler, that I could tell if a string was under-performing at a glance.
So I got a bunch of these, ( still awaiting installation, thanks COVID):
https://www.aliexpress.com/item/32967098638.html?spm=a2g0s.12269583.0.0.2897f991NqCK6H
The idea is to mount them all in a enclosure, monitoring each combined 30A string and to be able to tell if a string is under-performing with a passing glance.
I’ll label each meter with typical noon values at various dates, (or something along those lines).
They have gone up over a dollar each since I bought mine.
Go here for an affordable DIY meter : www.era-energytech.com