Hi I have got a HM8018 LCR meter. There are options on it to measure inductance at different frequencies, I have no idea at which frequency should the inductance be measured to get an accurate reading? If an inductor is not in the circuit, why should its value depend upon frequency?
You meassure it at the frequency (or closest) at which you will be using the inductor in the circuit.
The different core materials introduce losses that increase with frequency. Usually a grade of core material is chosen for best results for the particular frequency band at which you want to use the inductor. At VHF or higher frequencies an air core is likely to be used.
Because no inductor is ideal. Why don't you try to measure the inductor at different frequency? Without detail informations, nobody can answer the question.
In case of doubt you'll want to measure the inductance in the frequency range where it's used.