If all of the shunts were identical, there are still some errors in the setup. Sensing the voltage near the supply for example adds some error, it will not vary like the temperature sensor placement or the biggest problem, inserting the shunts into the clamps.
To give you some idea of the variance of the jig, here is the plots showing the resistance across the entire 100 Ampere sweep for all of the 5mohm shunts.
Two of these shunts were from CEM branded meters. They appear to have the same diameter and length so we expect these two will behave the same. Only looking at these two, the first graph shows their resistance. The next plot shows their voltage drop. These two were very linear across the entire 100A sweep. The temperatures were within 70deg C which is better than I would expect as there is a large temperature gradient across the surface. Those clamps are a plated brass with lots of thermal mass.
One thing I wish I had explained was Watt density. We are looking at the power dissipated with how much surface area the part has. The Kunsuntest ZT102 and free HF meter both calculated out to 12W/in^2. The nichrome with even higher resistance really pushes this up and why it makes good toasters and hair dryers. Lots of heat in a very small space..
For the few people that are interested, I have attached the raw data I collected during these tests. Voltage, current, power and temperature. One file for each shunt tested.
I look forward to watching the video. Unfortunately at the earliest it will be Monday, or Tuesday night.
In no way have I seen the insides of as many DMM's as Joe but in cheaper ones the shunts seem to be made of copper or brass.
Unless they're made of materials accepted for shunts like Constantan, no wonder there's some variability.
Nice job, I enjoyed it.
What was the software you were using?
Nice job, I enjoyed it.
What was the software you were using?
I use LabVIEW.
Voltage drop measures at 10.00 Amperes
Using large body HRC fuses
Brymen, BM869s, 312mV
UNI-T, UT61E, 239mV, Modified
CEM, DT9939, 350mV
UNI-T, UT181A, 294mV
Fluke, 115, 280mV
AMPROBE, AM530, 353mV
Fluke, 107, 325mV
Other...
Cen-Tech, 98025, 131mV, No fuse
External Shunt, 10mV
I made one more attempt to further improve the UT61E by adding even more copper and reduced it another 20mV was all.
Joe, one more excellent video. Thank you for the work.
I think that Centech will start stamping their meters with "exclusive 100A fuse" in the 10A input. That or the input will actually be marked as 100A (20 sec max).
LOL, yeah. Instant upgrade of fuse and higher current rating. Weee!
Voltage drop of the meter test leads swept from 2 to 20 Amperes in 2A increments. One meter stands alone....
Is that Centech yellow/green?
Is that Centech yellow/green?
You bet it is. They could make the meter with 100A for a 20 seconds and if the shunt doesn't melt off the board, the leads would open.
I wonder how the probes included with the two Kasuntest meters would do. Better yet, I wonder what leads the 121GW will include.
You bet it is. They could make the meter with 100A for a 20 seconds and if the shunt doesn't melt off the board, the leads would open.
I wonder how the probes included with the two Kasuntest meters would do. Better yet, I wonder what leads the 121GW will include.
You should have filmed that.
on the 1.21GW That will be a good guess.
I have a pair of Probemasters on my 87-1, and a set of modified(cut off safety shroud) gold Brymen's on the 3456A, with a set of Fluke probes floating around. My biggest problem with the HF meter, is that the probes are too short
.
He mentioned they would start testing in January but I guess that was pushed out. Better to make sure they are happy with it before it gets released.
I did capture the lead tests. Here is the free cen-tech meter leads.
https://youtu.be/fQowDZstguw?t=1222
Current through the shunt, voltage across the shunt and calculated resistance compared with the original shunt.
Much lower Watt density. Note also the added copper in the terminals.
Checking alignment against the Brymen BM869s.
A nice and toasty meter. Brymen looking at the drop across the modified UT61E. The UT61E will over range a bit over 22 Amperes.
Does it reach 200mV at 20A like their claim in the Kasuntest manual, no. The fuse and shunt get pretty warm with 10W but I ran it like this for a five minutes with no problems.
The Kasuntest KT6000 at 22A. 2 more Watts.
Where did you get the manganin sheet from?
Where did you get the manganin sheet from?
Came from a friend of mine. Looks like you can order wire or sheet stock of pretty much any size. I plan to make a video of the 61E but am still waiting on the proper fuses. This is were a lot of the heat is going now. Old 15A Fluke fuse, surprised it survived over 20A.
Measuring 20A with the UT61E. This meter is starting to look as bad as my UT90A.