Standard Electronics Tests Before and After a SPARO Run
In an effort to gather data for the prevention and diagnosis of bolometer
array electronics malfunctions, the following quick tests should be performed
before and after each cooldown. The tests are simple, but provide a nice
sanity check. These tests are done without mounting the preamps and without
powering the JFETs.
The first test involves checking each pin on each preamp connector(on the
dewar) for shorts to the vacuum case. The only pin that should be shorted is
pin C. This pin is shorted directly to case in our grounding scheme.
The next test is to check the resistance between the common bias line(pin A
on each connector) and the ground of each bolometer. The pins for each detector
ground are listed in the table below.
Detector
|
Pin for Ground
|
| D9 |
K |
| D8 |
M |
| D7 |
P |
| D6 |
S |
| D5 |
U |
| D4 |
W |
| D3 |
Y |
| D2 |
a |
| D1 |
b |
At room temperature, the bolometers have zero resistance. Thus, the resistance
between the common bias line and each bolometer ground should simply be equal
to the bias resistance, which in the case of SPARO is 20M. See the
circuit diagram for a detailed look at
the circuit.