Can we use more than one standard weight for daily verification of weighing bal

Yes. There should be atleast three standard calibrated weights for daily internal calibration

Max operating range for 30 kg balance is 24 kg.can we calibrate this balance with 24 kg weight by using three standard weight.i.e 20+2+2=24kg.

yes we can calibrate it by using given weight .because there is no standard calibrated weight of 24 kg so that we can use the set of 20+2+2 kg,

Yes, you can use but it should be certified by metrology department.

Scientifically only one test weight is sufficient for daily check whose weight is close to the balance capacity

But the common practice is to use 3 test weights which cover the working range

It is sufficient to use (20+5) since it is not obligatory to obtain exactly the 24 kg

It is not preferred to use many test weights to obtain a certain weight

(i.e 1 better than 2 better than 3)

But no problem

But take care of calibration certificates and the sum of errors and uncertainties of more than 1 test weight