An "E overload", or potential overload, can actually be one of either two conditions: either 1) the maximum input voltage (±10 V for most) of the differential electrometer has been exceeded, or 2), or the compliance voltage (the maximum amount of voltage the power amplifier can provide across the working/counter interface) is at its maximum. The E overload light will not distinguish between these two different conditions, so it is the responsibility of the user to determine which is the more likely cause. One special note: if the leads are not connected to a cell, the voltage reading on the display of systems will "float" randomly, and may report an E overload under these conditions. This does not damage the system, and occurs because there is an open loop in the differential electrometer circuit; this would cease if you were to connect the working and reference electrode leads or connected a dummy cell across the leads.

An E overload due to exceeding maximum input of the electrometer is usually seen when working with a low impedance cell (i.e., fuel cell or battery) in galvanic mode.

An E overload due to exceeding maximum power amplifier output is usually a more serious condition because the full compliance voltage is being applied to the cell, causing possible damage to your electrode. This condition is most often caused by a bad reference electrode or failure to connect the reference electrode. With out a reference, the power amp continues to pump current into the system until it either overloads or reaches the desired potential (which it obviously can not do without the reference in place). Another common occurrence of this type of E overload is when working with highly resistive organic electrolytes. Again, the power amp is pumping current trying to achieve the requested potential at the working electrode, but it must also overcome the IR drop between it and the working, which can consume many volts depending on the resistance and the distance. To overcome this situation, reduce the distance between the counter and working electrodes.