Shunt For Multimeter

The current range in multimeters, par- ticularly the more inexpensive ones, is restricted by the load limits of the internal shunts to 1-2 A.The photo shows how eas- ily a precision heavy-duty resistor from Dale or RCL (0.1 52; 20 W; 1%) may be used as an external shunt. These resistors were not designed for this purpose, but they are much cheaper than custom made shunt re- sistors. The 20 W rating applies only, by the way, if a heat sink is used: without that its rating is only 8 W. The maximum current through the device on a heat sink is about 14 A; the larger versions draw up to17.5 A. When mounting the shunt, make sure that the test terminals as well as the device terminals are soldered properly, otherwise the resistance of the terminals is added to the shunt. ELEKTOR ELECTRONICS JULY 1989 SUPPLEMENT TEST & MEASUREMENT SHUNT FOR MULTIMETER