PC11 Test Board for the A101

The PC11 is a printed circuit board designed to facilitate testing of the A101. In addition to testing circuitry, it provides component locations for use with detectors. Ground plane construction minimizes external pick-up.

INPUTS
IN: Detector input; PIN 12; should be AC coupled with a high voltage capacitor (500 pF - 1000 pF).
DET: Provides post to connect the detector and input capacitor.
TEST IN: Input to test circuit as described in specifications.
Vs: PIN 2; supply voltage (+4 to +10 VDC).
H.V.: Provides post to connect the detector to the high voltage supply through a resistor.

OUTPUTS
+ OUT: Positive, TTL type output from PIN 5.
O.C. OUT: Negative, open collector output from PIN 6. (Must be connected through 1 kohm to Vs.)
BUF OUT: Positive output through a Buffer/Line Driver IC from PIN 5. 

COMPONENTS
CV: Filter capacitor.
RP: Pullup resistor (1 kohm).
C: Test capacitor (2 pF).
R: Test pulse termination resistor (50 ohm).
RT: Threshold adjustment resistor.
CW: Pulse width adjustment capacitor.
CD: High voltage detector coupling capacitor (user supplied).
RB: Detector bias resistor (user supplied).
U2: Line Driver TPS2829.

The A101 can be tested with a pulser by using the small 2 pF test capacitor to inject a test charge into the input. The unit will trigger on the negative-going edge of the pulse, which should have a transition time of less than 20 ns. Either a tail pulse with a much longer fall time (>1 μsec) or a square wave may be used. If a square wave is used, triggering on both the positive and negative going edge will occur for large pulses. Charge transfer in the test circuit is according to Q=CV where Q=Total amount of charge, C=Capacitor, and V=Voltage.

Typical test circuit

Examples: 1) A 0.25 volts test pulse into 2 pF test capacitor will transfer 0.5 pC into the input of the A101. 2) Using the 2 pF test capacitor, the nominal threshold of the A101 will be at 80 mV. CAUTION: Use only the TEST INPUT to test the A101 with a pulse. DO NOT connect the test pulser to the input directly or through a large capacitor (>100 pF)as this can produce a large current in the input transistor and cause irreversible damage.