30A Shunt-Transducer 10mV/A 0.5% for DMM/Scope usage

[Cymaphore]

Hi,

I built something for personal use:

  * Shunt transducer based on Isabellenhette PBV R010
  * 10mV/A, 0.5% Tolerance
  * Temperature coefficient <30ppm/K
  * Rated current: 30A
  * Dimensions (without cables): 45 x 30 x 10 mm
  * Overall length: 570 mm
  * Measurement category: CAT II 1000V / CAT III 600V (due to the load side connectors, CAT IV 1000V possible with non-stackable jacks on the load side)
  * Pulse power rating: 2 joule / 10 ms
  * Load: Yellow, Blue; Stackable
  * Sense: Red, Black

These shunts from Isabellenhütte are quite impressive, I use them in a variety of applications. I have a couple of wild wirings on the lab bench for cases where neither the current clamp, nor the DMM current measurements are convenient (long-time measurements, very high in-rush currents, specific fuse-needs, etc.).

So I decided to turn me one of these shunts in a decent portable and appropriately rugged adapter. I intentionally left out any fusing and instead have a couple of Fuse adapters that I can plug in between when needed.

Load side has stackable connectors for flexibility. If it would be intended primarly for scope usage, coax + bnc would of course be more appropriate.

Measurement category rating is of course done by myself based on the specs of all parts included and no warrenties there.

Heat sink is dimensioned based on gut feeling, hope and space requirements (DMM bag).

It can measure 20A indefinitely without even getting significantly warm, I had it run on 30A for longer durations without any issues or deviations in precision. Inrush currents of about 200A have not been an issue so far. I haven't yet calculated or rated it's absolute limits.

It will be damaged or destroyed if used wrongly. It's an unfused measurement adapter and not intended for "poking arround for stray currents" use cases.

Precision of the Isabellenhuette shunt is as usual remarkable.

Parts:

  * 2 x Aluminium plates, approx. 40mm x 24mm
  * 1 x Isabellenhuette PBV R010 0.5% 0.01 Ohms shunt
  * 4 x Silicone measurement wire, 2,5mm² diameter (red, black, blue, yellow)
  * 2 x Staeubli / MC Protected lab plugs (red, black), 32A rated
  * 2 x SLS425-SE/M Stackable plug/jack connectors, 32A rated
  * 2 x Self adhesive heat conduction pads
  * approx. 80mm Heat shrinking tube, 5mm diameter, 3:1, 600V
  * approx. 50mm Heat shrinking tube with glue, 30mm diameter, thick-walled, 1000V

Assembly:

As seen in the pictures, not really complicated. After soldering and cleanup, I put on the heat conductive pads, put it to the aluminum plates and used hot glue to fill the gaps and have it stable for the shrinking of the outer covering. Be extra careful that no glue gets in between the aluminum plate and the shunt/heat conductor. Handling of the thick walled outer tube with integrated glue can be tricky but is worth the effort (very good insulation). Be extra careful not to overheat while soldering and hot-airing.

Best regards,
Martin

[Cymaphore]

Hi,

Since I still had a piece of the aluminium band left over, so I decided to turn another PBV Shunt into that packaging. By the way, the aluminium band is actually left over from renovation of our bathroom, I used most of the rest for similar simple heat sinking things and other stuff. It works quite well for that.

In the picture you can see both shunts, now labeled, dymo tape covered with transparent scotch tape to avoid the letters from being scratched or wiped off by chemicals. The slightly larger one is the new 100mV/A one. It's slightly larger because I just cut the rest of the aluminium in half. :-)

Out of interest I used some left over Arctiv Silver 5 as thermal compound. I wanted to see, if it is usable for that kind of a screwless packaging. Or if it will be tainted by hot glue or the heat shrinking tubes glue or affected by the shrinking heat. Thermal compound was once again applied to both sides of the shunt before putting it in between the heatsinks.

This time I used a 100mOhm PBV to make me a 100mV/A Shunt rated for 10A. Therefore, solely based on spec, it's measurement category is slightly lower then the other one.

Also I managed to arrange the entrypoints of the sense and load cables a bit nicer than before and was able to join the middle section on both sides while the tube was still hot enough.

To verify the arctic silver I'm currently running a burn-in test on it at 5A.

• Ambient Temperatur arround 30°C, Type K sensor at the surface of it, centerpoint, where the Shunt sits.
• Applying 5A to it until the temperature didn't change for a longer duration.
• Temperature settled down at about 55°C
• Burn in with 5A ran for all in all approx. 55h so far, with a couple of cool down phases (accellerates the burn in of the compound) and interruptions for inspections and the photo.
• Currently it settles at about 49.6°C
• Burn in phase not yet completed

This continous drop in temperature is a good sign, that the compound was not significantly affected by the heat shrinking process and is actually participating in heat transportation. Once the burn-in is completed, the temperature should be even lower.

Why I checked this: Arctic Silver 5 can be squeezed away under pressure, possibly going somewhere I don't want it (no electrically measurable sign of that, but hard to tell without physical inspection). It is paste-like and therefore a bit more difficult to use in this kind of an assembly. Also it requires up to 200 hours of burn-in time to unfold its maximum effectiveness. The temperature drop during burn-in is always a good indication.

Best regards,
Martin

[Cymaphore]

Hi,

Now about 1/3 of the burn-in time (at 5ADC) is completed, so I had it underwent some "live trial".

• Testee: 2.8kW Tumble dryer; Runs at roundabout 11A (230VAC) in highest mode, that dryer works right at the edge of what european schuko plugs can withstand permanently; Every direction change of the trommel causes a peak of 40-50A
• Connected to the shunt via another adapter
• Running in highest drying program for about 1h
• Temperature monitored once again right in the middle
• Ambient temperature about 23°C

Initially, as to be expected with Arctic Silver 5 that has not yet fully been burnet in, temperature went up quite high. At peak I measured about 87°C on the surface.

After a couple of minutes at about  10.8A with regular short bursts of 40-50A, it began to gradually go down. I could actually observe the thermal latency get smaller during the test (time between a change in current and consequent change in temperature).

At about 1h the temperature remained at about 60°C.

Burn-in at 5A now continues, the temperature is now significantly lower at about 44°C.

So the Arctic Silver 5 seems to work and my 10A rating for the thing looks valid.

Best regards,
Martin

[schmitt trigger]

Very nice workmanship!

Are you planning on selling them?

[Cymaphore]

Very nice workmanship!

Are you planning on selling them?

Thank you

No, just made these for myself for a gap in measurement I percieved lately. Countinous DC currents of up to 30A, very long logging duration (expensive to do that with a clamp meter / transducer properly) and irregular current bursts that would blast an HRC fuse.

Just want to share it in case someone faces similar problems and want to build one for himself. Most of the parts involved are relatively inexpensive and widely available, especially if you build it for smaller voltages and not high voltage style like I did.

Best regards,
Martin

[2N3055]

To paraphrase Crocodile Dundee : "That's  not a shunt!!  This is a shunt !!".... 

Jokes on a side, Isabellenhütte resistors are very good and it will make nice shunt.

Mine is a "bit" bigger : RUG-Z-R002-0.1-TK1, used to measure up to 100A (200mV) with very good stability. Plan was to get it calibrated in a certified lab, but never did that. It was calibrated for internal use and is doing very good job.

One more thing about both resistor you used and one I used: they are made to be as noninductive as they could (they are metal foil type), and with short wiring can be used for AC with good results. What exactly bandwidth it would have would need to characterised, including all the wiring used..

Anyways, if you do long term current measurement, you might need to consider cooling it even more, for better linearity... Of course, that is if you need additional precision and stability.

[TiN]

"Now, now, easy there".





Current Ranges = 10 to 100 Amp.
Frequency Range = DC to 100 kHz.
Maximum Variability of Output Voltage (Percent) = DC    +/- 0.001% , 10Hz to 1KHz    +/- 0.002%, 1KHz to 10KHz    +/- 0.004%, 0KHz to 20KHz    +/- 0.02%, 20KHz to 100KHz    +/- 0.2%

[2N3055]

"Now, now, easy there".





Current Ranges = 10 to 100 Amp.
Frequency Range = DC to 100 kHz.
Maximum Variability of Output Voltage (Percent) = DC    +/- 0.001% , 10Hz to 1KHz    +/- 0.002%, 1KHz to 10KHz    +/- 0.004%, 0KHz to 20KHz    +/- 0.02%, 20KHz to 100KHz    +/- 0.2%

LOL...

I was making a joke, as we both made a shunt using Isabellenhütte resistors..
Low cost, homemade..
I got my RUG-Z-R002-0.1-TK1 new from Distrelec for very good price of 70 € few years ago.

Those 4 coaxial transfer standard shunts cost more than whole lab of instruments..... 

Of course, a bought Keysight 3458 will be better than homemade multimeter...

[Cymaphore]

My whole point was that the shunt easily fits in the bag of my S2 (and the other meters), not the other way around :-)

Those shunts are entirely different beasts, thank you for the pictures and impressions!

[2N3055]

My whole point was that the shunt easily fits in the bag of my S2 (and the other meters), not the other way around :-)

Those shunts are entirely different beasts, thank you for the pictures and impressions!

Like I said, I found it funny how I, also, made an shunt using Isabellenhütte resistor, but not exactly the same.

As I commented, I like it how you shown members here (that span from total beginners to seasoned pros)  how easy is to buy a good resistor and make a shunt that will enable you to measure currents that will be hard for internal shunts in multimeters.

I actually have a handful of those Isabellenhütte resistors (pretty much same type you used) that I use to make dynamic current measurements with my Picoscope...

Regards

[Cymaphore]

Same here :-)

I hook these things up to PicoScope as well if Peak Hold on the DMM is not suitable or I need to observe some follow up bumps or effects regarding switching that the slow current clamp would just miss. Has it's limits and side effects, of course, but it's simple and inexpensive overall.