Local front panel control

Remote control - analog signal

Remote control - digital signal

Local front panel control

        Local control means using onboard potentiometers to set the output voltage/current. Some modules contain user-accessible potentiometers (ME, MRC, MRD, etc.), allowing the user to set voltage/current. Most of Weismann's rack mount units include a fully functional front panel with a locking counter dial to set the desired voltage/current.

       So if the power control circuit is analog and a front panel potentiometer is used to set the power supply, that potentiometer determines the design resolution achieved.

Because the resistive element presents a continuous contact surface rather than discrete turns of wire as in a wirewound potentiometer, the arc brush of a cermet (ceramic/metal) or plastic film potentiometer can be set closer to the target value value.

       Most modular power products with local design capabilities use cermet or plastic film potentiometers, so these devices can technically achieve the "near infinite resolution" capabilities required by the manufacturer. The potentiometer used on most rack units is a wirewound Bourns potentiometer (3590 5kΩ, 10 turns) with a resolution specification of 0.025%.

       If the modular or rack-mounted power supply product has a standard digital interface (RS-232, Ethernet, or USB), the power control circuit is digital. Even though the front panel generates an analog signal to control the power supply, the signal is converted to digital at the bit resolution used by the digital interface and control circuitry.

Remote control - analog signal

       If the power control circuit is analog and a remotely generated analog signal is used to set the power supply, the user-generated analog signal will determine the resulting design resolution.

       If the modular or rack-mounted power supply product has a standard digital interface (RS-232, Ethernet, or USB), the power control circuit is digital. Even if an analog signal is provided to a power product, the signal is converted to digital at the bit resolution used by the digital interface and control circuitry. So the resolution limit can be the bit resolution of the user-generated analog signal or the power supply, whichever is greater.

Remote control - digital signal

       If the modular or rack-mounted power supply product has a standard digital interface (RS-232, Ethernet, or USB), the power control circuit is digital. Designing a power supply through a digital interface results in limited bit resolution for the digital and control circuits in the power supply product.