  A calibration method aimed for the differential nonlinearity (DNL) error of
the Low Energy X-ray Instrument (LE) onboard the Hard X-ray Modulation
Telescope (HXMT) is presented, which is independent with electronic systems
used as testing platform and is only determined by the analog-to-digital
converter (ADC) itself. Exploring this method, ADCs that are used within the
flight model phase of HXMT-LE can be calibrated individually and independently
by a non-destructive and low-cost way, greatly alleviating the complexity of
the problem. As a result, the performance of the energy spectrum can be
significantly improved, further more, noise reduced and resolution enhanced.
