Each printhead has an average resistance (R_{AV}) that is the arithmetic mean of the resistances of all the heater elements on that printhead.It is typically printed on the label of the printhead. The average resistances of actual printheads vary significantly regarding the nominal average resistance for that printhead model. At a fixed heater voltage, average power will have the same range of variation as resistance, because P=V^{2}/R_{AV}. If all printers used the same pulse width (T_{ON}), then the print energy would vary by the same range because Energy = P x T_{ON}. This uncompensated variation in print energy would cause a noticeable variation in print image quality and an unacceptably short life for printheads at the low end of the average resistance range.
The simplest way to compensate for variable printhead resistance is to use a variable voltage power supply and adjust the voltage (V_{H}) at printhead installation so that the print power is constant. This print power, expressed as power density, would be a horizontal line on the MOCC and maximum pulse width could be easily read from the MOCC.
More typically, printers use a fixed voltage power supply. Therefore print power becomes a range on the MOCC. The following example is for a KPA808MPA1 printhead. Its heater area is 0.11mm x 0.132mm = 0.01452mm^{2}. The specified average resistance is 660 ohm +/ 15%. The typical operating voltage (V_{H}) is 24V. The voltage loss (V_{L}) within the driver IC is specified as 0.9V, which for simplicity is always specified as a constant because it is small compared to V_{H}. The net power that generates heat in the heater element heater, (V_{H}V_{L})^{2}/R_{AV} is determined by the voltage drop across the heater element (V_{H}V_{L}), which is the same parameter that was controlled when the MOCC data was produced. The table below shows the calculation of three power density levels starting from minimum, center and high R_{AV} values.


High Power 
Mid Power 
Low Power 
Nominal R_{AV} 
Ohm 

660 

+ /  15% Nominal R_{AV} 
Ohm 
561 
660 
759 
Voltage drop = (V_{H}V_{L}) 
Volt 
23.1 
23.1 
23.1 
Power = (V_{H}V_{L})^{2} / R_{AV} 
W/dot 
0.951 
0.808 
0.703 
Heater area 
mm^{2} 
0.01452 
0.01452 
0.01452 
Power density 
W/mm^{2} 
65.5 
55.6 
48.4 
The resolution of this printhead is 8 dots per mm, making it a 200 dot per inch printhead. The MOCC below duplicates the 200 dpi MOCC shown previously. On it are plotted the three power density levels as horizontal red textured lines.
The printhead specification shows pulse width as 0.26ms at 0.841w/dot applied power and it shows 0.032w/dot as the power loss in the driver IC. Therefore net power = (0.8410.032) = 0.809 w/dot and power density = 0.809 / 0.0145 = 55.7 w/mm^{2}. This point falls on the 1.0ms cycle time line confirming that the MOCC and the specification agree on this single point.
If a printer design does not choose to adjust pulse width as a function of average resistance, then the single pulse width for a cycle time is determined by the intersection of that cycle time line with the maximum power level line. The minimum available print energy is given by the product of that single pulse width times the minimum power level.
For example, Kyocera routinely assumes that 24 mJ/mm^{2} is the energy density required to darken typical label media. A dotted line marked by purple diamonds shows this constant value on the above MOCC. The pulse width that will darken this media at all power levels is given by the intersection of the media line with the minimum power level, in this example at 0.5ms. How fast can this nonadjusted printer go while still achieving a long printhead life? The cycle time that will allow 0.5ms pulse width at maximum power happens to be visible without interpolation as the blue line (marked by "X"s) for T_{CY}=5.0ms, which is approximately 1 ips. This would not be acceptable in today's competitive bar code printer marketplace.
Note that the slope of the constant required media energy line is steeper than the slopes of all cycle time lines. If the printer design continuously adjusts the pulse width as a function of average resistance to give a constant print energy of 24mJ/mm^{2}, then the print speed is determined by the cycle time line that intersects the maximum power line at 24mJ/mm^{2}. This unknown cycle time is between 2.0 and 5.0 ms, perhaps about 2.8ms. The formula for calculating print speed (ips) is ips = (1000) / (T_{CY} * lpi). The print line density in this example is 8 lines per mm or 203 lpi. Then print speed equals 1.76 ips, a 76% improvement. The print image quality would most likely be better, because, without adjustment, the print energy would be excessive at higher power levels. 