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Trimming shunt resistor

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Nabilah Etong

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Hi,

I'm new in the forum. Currently I'm doing a project on development and optimisation of a precision trimming process for manganin shunt resistor. The aims is to develop trimming process to adjust the tolerance of shunt between 5% to +/-1%. I want to know:

1. What is the best options to trim the shunt resistor (which used in smart energy meter)?
2. Why manufacturer didn't produce shunt with +/-1%? Is there any specific reason for this?
 

dick_freebird

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I doubt that a volume manufacturing process can do
better than the incoming sheet metal thickness tolerance,
and if you wanted it "pre-trimmed" you'd have to pay a
higher price. I guess the meters get sold well enough
with couple-% accuracy (though I bet the electric co
likes a bias toward a high reading).

I'd say a riffling file and a 4-wire resistance reading
is an easy way to go for a one-off. Presuming your
initial value is on the low side. There's not much help
for a high reading, except maybe solder-wetting a
region to reduce overall value (and you'd perhaps
add some tempco error by the dissimilar TCR).
 

FvM

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Firstly I don't agree with the assumption of 1% or even better shunts being unavailable. Probably not from all manufacturers.
Secondly, technics like grinding, milling, sand blasting, laser cutting are well suited for resistor trimming and can be automated.
 

tpetar

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Nabilah Etong

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Firstly I don't agree with the assumption of 1% or even better shunts being unavailable. Probably not from all manufacturers.
Secondly, technics like grinding, milling, sand blasting, laser cutting are well suited for resistor trimming and can be automated.

Do u know any manufacturer who produce shunt with lower tolerance?
 

Nabilah Etong

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1. Depends on the value of resistor and its nominal current and its tolerance out of the factory.
2. Cost
Frank

Thanks Frank. The resistor value in range of 0.1 to 10 mOhm. The resistance tolerance is +/-5%.
Currently I tried abrasive trimming but wonder if there is any other ways to do it as I don't thing I can used that technique if I want to produce shunt resistors in large quantity.

Is there any other reason than high cost? If cost is the problem, then I don't think I can bring the shunt with 1% tolerance or better to production line right?

- - - Updated - - -

E.g. Isabellenhuette https://www.isabellenhuette.de/en/precision-and-power-resistors/
or Vishay, Caddock
There's at least a large offer of 1% shunts, and some tighter tolerated.

Thanks. Been looking on Isabellenhuette and Vishay before.
Will look on Caddock too. Not sure if I can find any manufacturer from UK itself.
Trying to find any manufacturer that produce shunt resistor in smart energy meter with 1% tolerance so that I can do comparison but up to now, still didn't see any.

- - - Updated - - -


I attached the resistor spec that I will used for trimming.

specification.png

Rated current (dc / ac rms) = 300A
Output voltages = 30mV
Ohmic value = 0.1mΩ
Tolerance = 5%
Operating temperature range = -55 to 170°C
Inductance = <1nH typical
Thermal EMF = 3μV/°C
 

sokrat

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Hi All,

I have some Experience in the electronic energy meter design, I used a shunt resistor 200uohm and the tolerance I think 5% but the tolerance for shunt was not critical(depend on the Meter Class ) because you should make calibration for every meter during production to avoid the tolerance, and the meter has two measurement element CT and Shunt and the shunt USED for measure the return current in case of Tampers only.
 
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