Doesn't a pointer scale indicate the weight on the scale?
The way you're trying to solve indicates the use of a set of scales with two dishes;
but problem states that's not allowed!
Anyway, IF a regular weigh scale is allowed, ONLY one weighing is required.
Like, if regular coins weigh 10 (then the counterfeit = 11), if you put one from
each stack on the scale, the scale will indicate 101 (9 *10 + 11).
Please check your problem and repost properly and clearly.