  This work illustrates and compares some methods to measure the most relevant
parameters of silicon photo-multipliers (\sipm{}s), such as photon detection
efficiency as a function of over-voltage and wavelength, dark count rate,
optical cross-talk, afterpulse probability. For the measurement of the
breakdown voltage, $V_{BD}$, several methods using the current-voltage $IV$
curve are compared, such as the "IV Model", the "relative logarithmic
derivative", the "inverse logarithmic derivative", the "second logarithmic
derivative", and the "third derivative" models. We also show how some of these
characteristics can be quite well described by few parameters and allow, for
example, to build a function of the wavelength and over-voltage describing the
photodetection efficiency. This is fundamental to determine the working point
of SiPMs in applications where external factors can affect it.
  These methods are applied to the large area monolithic hexagonal SiPM
S10943-2832(X), developed in collaboration with Hamamatsu and adopted for a
camera for a gamma-ray telescope, called the SST-1M. We describe the
measurements of the performance at room temperature of this device. The methods
used here can be applied to any other device and the physics background
discussed here are quite general and valid for a large phase-space of the
parameters.
