A calibration test was done on NINO preamp board in order to understand 
its functioning as well as to obtain its
input charge versus threshold relationship.

The test circuit is shown by nino-ckt.jpg.

The procedure followed is:

1. We adjust using the attenuator the required pulse output (in mV).
2. We can compute the charge(Q) injected, by multiplying this voltage(V) 
by the series capacitance(C=10pF).
3. Give this input to one of the NINO channels.
4. Look at the ORed output and adjust the on-board threshold.
5. We do this till the ouput just (dis)appears.
6. We will measure this threshold at its test point.
7. The measurements are plotted.

The plot is shown in nino-plot.jpg.

On the X-axis is the NINO threshold voltage. On the left Y-axis is the 
charge injected(in fC), while on the
right Y-axis is the (atenuated)pulser output (in mV). A linear fit is also 
done. The relation obtained was:

charge = 0.0248 * threshold + 0.1684

It matches quite well with the value specified by the designers (i.e ~4mV 
threshold per 1 fC of charge).

The errors on the measurements are mainly due to inaccurate reading of the 
input pulse height on a CRO.