Amplitude is a very simple measurement of subtracting the range (high - low) of a candle by some other data from that candle. in this case, we use the midpoint of the candle, so the calculation is (high - low) / (high + low)/2 . This isn't a new concept, but I could not find this study anywhere so I decided to add it myself.
Open-source script

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Want to use this script on a chart?
//A simple measurement of amplitude
//You can use this to help gauge volatility in the market
//Change the divisor as you wish

study("amplitude")
amplitude = ((high - low)/((high+low)/2))

plot(amplitude, style=histogram)