COMPARISON OF THREE DIFFERENT SHUNTS DESIGN FOR AC-DC CURRENT
TRANSFER

Lucas Di Lillo1, Héctor Laiz1, Eliana Yasuda1, Ricardo García2
1Instituto Nacional de Tecnología Industrial, INTI, Argentina, ldili@inti.gob.ar
1Retired, Instituto Nacional de Tecnología Industrial, INTI, Argentina, garcia-levi@arnet.com.ar



Abstract: In order to update and improve INTI’s AC-DC
current transfer capabilities, we developed three different
types of 5 and 10 A shunts for the AC-DC current transfer
measurements included in a new AC-DC Transfer Step-Up
scheme. The construction details and the measurements
results are described in this paper.


Key words: AC-DC current transfer, current measurement,
current shunts, thermal converters
1. INTRODUCTION
At Instituto Nacional de Tecnología Industrial (INTI),
ac-dc current transfer measurement have been performed
using thermalconverters (TVC) and shunts.
Thermalconverters reach current levels up to 10 mA. In
order to increase the measurements capabilities, higher
current thermalconverters [1] or low thermal current
converters in combination with shunts are necessary.
The appearance in the market of new equipment capable
of measuring high currents with high accuracy in a
frequency range up to 100 kHz, creates the demand for
calibration at these levels.
The INTI primary standards of the ac-dc current transfer
difference consist of TVCs for lower currents (less than
100 mA) and TVCs combined with shunts for higher levels
(100 mA to 10 A) [2]. The INTI’s calibration and
measurements capabilities in this field are from 3 mA to 10
A and in frequency are from 10 Hz to 100 kHz with
uncertainties from 3 V/V to 40 V/V [3]. Although there
are several commercial shunts available in the market, INTI
decided to build their own. In this paper we are going to
show some ac-dc current transfer difference results and three
different designs for 5 A and 10 A shunts constructed and
measured al INTI.
2. EXPERIMENTAL RESULTS
The shunts were characterized by measuring their ac-dc
current transfer difference at 5 A, in a frequency range from
10 Hz to 100 kHz. The diagram of the measuring system can
be seen in [4].
Fig.1 shows the ac-dc current transfer difference for
three shunts measuring at 5 A. Two of them were design for
5 A and the other one was design for 10 A.
-200
-150
-100
-50
0
50
0,01 0,02 0,03 0,1 0,5 1 5 10 20 30 50 70 100
Frequency (kHz)
AC
-D
C c
ur
ren
t tr
an
sfe
r d
iffe
ren
ce
( 
V/
V)
TVC+SH5A(a)
TVC+SH10A(b)
TVC+SH5A(c)
Fig.1: AC-DC current transfer difference at 5 A for three different
shunt design.

3. DESIGN CONSIDERATIONS
All the shunts constructed at INTI were design for an
output voltage of 1 V for nominal input current.
A diagram of the shunt identified as TVC+SH5A(a) can
bee seen in Fig.2. The arrows indicated the flow of the
current and the drop voltage in the resistors [5]
Fig.2: Details of the construction of 5 A shunt

In this case, surface-mount resistors (SMD) with values of
33  were mounted in holes through the surface of the
double-sided circuit board and soldered to the copper layers
on both sides. The number of resistors was selected in order
that the heat dissipation for each resistor was ¼ of the
nominal power. This is to avoid level dependence errors due
to the increase of the temperature with the increase of the
input current. The resistors were placed in the perimeter of
the circuit board to make the current distribution as
symmetrical as possible. An UHF connector was placed in
the middle of the circuit board (left side of Fig.2.) for the
input current and an N male connector was placed for the
output voltage (right of Fig.2).
The second design, identified as TVC+SH10A(b) can be
seen in Fig.3. In this design, Vishay metal film resistors of
10  with low temperature coefficient and low tolerance
were used. The resistors were soldered between two plates.

Fig.3: Details of the construction of 10 A shunt

The third design was used in the shunt identified as
TVC+SH5A(c) ) and can bee seen in Fig.4.

Fig.4: Details of the construction of 5 A shunt

This design is similar to the one used in the NMI of
Russia and Sweden [6]. The shunt consists of 3 plates
connected by ribs. The plates and the ribs are made of
double side cooper layers. In the ribs, Vishay metal film
resistors with nominal values of 10  were soldered
between the two output plates, connecting them in parallel.
The arrows show the flow of current and the drop voltage in
the resistors which is connected to the TVC.







3. CONCLUSION
Three different types of shunts used for ac-dc current
transfer were measured. Results shows that the shunt
identified as SH5 A(a) shows small ac-dc transfer difference
in the hole range of measurements.
With this new set of shunts we can carry out multiple
measurements in a same current range, that allow us have a
redundant system, useful to obtain lower uncertainties
through statistical tools.
Details analysis using lumped circuit of each type of shunt
will be presented in the full paper.
REFERENCES
[1] Laiz, H.; Wunsch, T.F.; Kinard, J.R.; Lipe, T.E., “1-A and-
120 mA thin-film multijunction thermal converters”, IEEE
Trans. Instrum. Meas. Vol. 54, No 2, pp. 803-806 April 2005.
[2] Di Lillo,L; Laiz,H; García,R; “New AC-DC current
transfer set-up”, VI Semetro, Rio de Janeiro, Brasil,
September 2005
[3] www.bipm.org
[4] M. Klonz, T.Funcki, L. Scarioni “Quartz planar
multijunction thermal converter as a new AC-DC current
transfer standard up to 1 MHz”, IEEE Transactions on
Instrumentation and Measurements, Vol.54, Nº2, Apr
2005
[5] Lind, K, Sorsdal,T, Slinde,H,”Design, modeling and
verification of high performance AC-DC current Shunts
from inexpensive components”, IEEE Trans. Instrum.
Meas. Vol. 54, No 1, pp. 176-181 January 2008.
[6] Mansten, T et all; “new ac current shunt of MIKES”,
CPEM 2002, Conference digest.