Question

Okay for this question, I obviously don't need a quantity because I dont have any, but how would I approach this question in lab if asked:

"Quantify the scatter (or range) of the three resistance values as a percent of their averages"

I don't know what my answer should look like or what I'm supposed to do with the resistance values

Answer 1

Different printheads of the same model will have different average resistance values, as shown on the label of each printhead. This label average resistance value will be within some percent of the nominal average resistance, as shown in the specification. Better thermal printers will compensate for this variation between heads by adjusting either the heater voltage or the pulse width. This is discussed in detail elsewhere in connection with maximum operating conditions.

The resistance variation among heaters on the same printhead will be limited by the specification. For bimodal printheads, the signed difference between a heater's resistance and the label average resistance, expressed as a signed percentage of the label average resistance, will be within a percentage range. For example
- 10% < ? R / R_AV < +15% where ? R = (R- R_AV)
For gray scale printheads, sometimes the resistance variation among heaters on the same printhead is expressed as
|R_MAX- R_MIN| / R_AV
and is specified to be less than a certain percent.

Some specifications also limit the resistance difference between adjacent heaters. This would be expressed as
|R_n-R_n+1| / R_AV and would be specified to be less than a certain percent. Again R_AV means the label average resistance on the label.