A very important factor in structure to earth potentials, where errors in reading can be very costly. Overload Protection Advanced design features virtually eliminate the chance of damage to either meter from electrical overload on all volt and millivolt ranges, even the 1 mV range. Note that the ammeter shunts are not protected by the amplifier, and are therefore subject to damage by current overloads. The instruments are inherently more resistant to mechanical damage, and since both instruments are identical, one spare instrument can be used as a replacement for the other. Replacement instruments, if ever needed, are low in cost and readily available.
Pointers are knife-edge type.
Use of optional accessory external shunt extends the range of current measurements to 100 A and can be used with either meter. Circuit may also be used like an ohmmeter for checking continuity of test leads.