3 Operation
The XPPS module is very simple to use. In most cases, all that
is needed is to connect the XPPS to AC power, and connect the
preamplifier cables, being mindful of connector and cable current
ratings. For best results, it may be necessary to also connect the ground
strap to the associated signal processing electronics in order to
eliminate ground loop noise. Prior to connecting the AC power, it is
necessary to select the proper input voltage on the AC power input
module on the rear of the unit; see below for instructions. In most
cases, the voltage will be set properly prior to shipment.
3.1 Connector Current Ratings
Note that the XPPS front-panel DB9 connectors are rated at 2
Amperes per pin. As a rule of thumb, each connector should carry no
more than 1.5 Amperes on any voltage, no more than 3 Amperes total.
Note: It is always safest to split the load between all four DB9
connectors.
Current per
Voltage
Total
Current
Recommendation
< 1.5 A
< 3.0 A
Use one or more DB9 connectors
< 3.0 A
< 6.0 A
Use two or more DB9 connectors
< 6.0 A
< 12.0 A
Use three or more DB9 connectors
> 6.0 A
> 12.0 A
Use all four DB9 connectors
For example, consider a 26-element detector system that
draws 100 mA on +/-12 V and 50 mA on +/-24 V. The current
required at +/-12V is 2.6 A, and the current required at +/-24 V is 1.3
A. The total current is 3.9 A. At a minimum, two DB9 connections
must be made, however, the best cabling solution would use all four
DB9 connections.
3.2 Preamplifier Connector Pinout
The female DB9 connectors on the XPPS conform to the
standard pinout for detector preamplifier power connections:
Pin
Description
1 and 2
Ground
4
+12V
6
-24V
7
+24V
9
-12V
3, 5 and 8
Unused
