  Recently, the Istituto Nazionale di Astrofisica (INAF) has placed a contract
with Hamamatsu Photonics to acquire hundreds of Silicon Photomultipliers (SiPM)
tiles to build 10 cameras with 37 tiles each for the ASTRI Mini-Array (MA)
project. Each tile is made up of 8x8 pixels of 7x7 mm2 with micro-cells of
75um. To check the quality of the delivered tiles a complex and acurate test
plan has been studied. The possibility to simultaneously analyse as many pixels
as possible becomes of crucial im-portance. Dark Count Rate (DCR) versus
over-voltage and versus temperature and Optical Cross Talk (OCT) versus
over-voltage can be easily measured simultaneously for all pixels because they
are carried out in dark conditions. On the contrary, simultaneous Photon
Detection Efficiency (PDE) measurement of all pixels of a tile is not easily
achievable and needs an appropriate optical set-up. Simultaneous measurements
have the advantage of speeding up the entire procedure and enabling quick PDE
compari-son of all the tile pixels. The paper describes the preliminary steps
to guarantee an accurate absolute PDE measurement and the investigation the
capa-bility of the electronics to obtain simultaneous PDE measurements. It also
demonstrates the possibility of using a calibrated SiPM as reference detector
instead of a calibrated photodiode. The method to achieve accurate absolute PDE
of four central pixels of a tile is also described.
