How the ZM4 works
Broadly, the ZM4 regulator consists of a timer block, voltage comparison logic and a transistor output stage.
The timer block is responsible for overseeing the transition between the absorption and float stages, and is factory set from 40 to 80 minutes according to your battery capacity.
The voltage comparison logic continuously monitors the battery voltage and compares it to the voltage level you have selected with the adjustment control knob.
If it detects that the battery voltage has fallen below your set point, the output transistor stage will be turned on to increase the field current to the alternator.
Once the voltage level has been raised back to your setting, the field current is disengaged. Hysteresis is built into the comparison logic to ensure the feedback loop remains stable.
Any type of alternator can be run by this regulator, providing field current draw does not exceed 8 amps continuous or 16 amps intermittently. Most alternators only draw 1-3 amps max. Currently have an installation running 2 x 175 amp alternators off one ZM4.
Field Brush Configuration
The ZM4 N is a negative brush control system, this means that the positive brush requires power at all times and the theory is we control the negative brush which controls the output of the alternator as per the setting on the ZM4, A quick look at the colour of the board of the ZM4 will tell you which unit you have, GREEN is N Switching
The ZM4 P is a positive brush control system, this means that the positive brush is the field control and the negative brush is earthed
A quick look at the colour of the board of the ZM4 will tell you which unit you have RED is P Switching