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Will a liquid resistor have different values with simple DC voltage versus pulsed DC voltage? And do voltage levels affect the resistance of a liquid resistor?
For example, if test a liquid resistor with simple DC supply, will it have same resistance as when tested with pulsed DC?
It depends on the liquid.
If it's a liquid metal like mercury, gallium, molten solder or sodium, then it will behave just like a normal solid resistor (save for possibly some magnetohydrodynamic flow in either self or external magnetic fields, which will likely be negligible if not intended) which is the same for AC, DC, pulsed DC etc.
If it's a heterogenous fluid, like an aqueous solution or minerals disolved in a molten salt, then it depends on the chemistry of the solution and electrodes. Polarisation, that is a chemical concentration gradient in response to a current flow, near the electrodes will usually increase the voltage drop across that part of the solution, so looking like an increase in resistance. This will occur with DC, and will increase as the current continues to flow, resulting in high and changing readings. This is why AC is usually specified for measuring the resistance of a solution.
If the solution is compatible with the electrodes, for instance copper electrodes and a copper sulphate solution, then at low currents polarisation will be less significant. However impurities can cause problems, and practical electroplating solutions contain all sorts of other chemicals (technology, practical know-how, 'secret sauce') to make the process work better.
There are many cases where measurements of aqueous solutions often have their own field of practical knowledge, in addition to just 'measuring with AC', for instance moisture levels in soil, or heart waveform electrodes.
When the solution is very weak, 'plain' water for instance, the effect can be the other way, that electrolysis of the electrodes puts orders of magnitude more solute ions into the fluid, increasing the conductivity.
